I A Fi Cap Five-Y Issue: 200 As Appro ive-Yea Transm pability (2009 Year Annual Tra 09 ved by the ar Annu mission y Statem -2013) ansmission Capa e Authorit ual ment ability Statement ty for Elec 20 t (2009 - 2013) ctricity Re 009 egulation o 9 on 3rd Au ugust 2009 Page | 1 9
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This Transmission Capability Statement is provided by the Oman Electricity Transmission Company according to Transmission and Dispatch Licence Condition number 27 and in accordance to the Grid Code / Planning Code. The Statement describes in detail the transmission system capability over the coming five years 2009-2013. The Statement provides up-to-date transmission system data in order to identify those parts of the system, which offer the opportunity for future development of existing and potential users of the system.
In this Capability Statement the results of load flow and short circuit analysis are presented based on the planned system reinforcement to meet the demand forecast provided by Oman Power and Water Procurement Company and the distribution companies. The Statement presents complete solutions of all problems reported in the previous Five Year Capability Statement (2008-2012). By the end of the period covered by the present Statement, problems of line and transformer loadings, voltage, and fault current issues will be completely removed. Significant improvement has been introduced in the OETC grid model, e.g. updated project schedule, generation data, system data and control settings.
The existing and planned development in the generation and is transmission system is described and a new section for transmission system derogations is also included in the Statement.
3. Technical Requirements for Compliance with the Grid Code and Licence 22 3.1. System Frequency 25 3.2. System Voltage 26 3.3. Security of Supply 26
4. OETC System Design and Planning Standards 27 4.1 Oman Electrical Standard OES 11 27 4.2 Oman Electrical Standard OES 25A and 25B 27 4.3 Oman Electrical Standard OES 27 27 4.4 Oman Electrical Standard OES 32 27 4.5 Other Standards 28
5. OETC Transmission System 28 5.1 Existing 220/132 kV Transmission System 28 5.2 Future System Development Projects 30
5.2.1 Projects expected to be completed to meet the 2009 peak demand 30 5.2.2 Projects expected to be completed to meet the 2010 peak demand 30 5.2.3 Projects expected to be completed to meet the 2011 peak demand 31 5.2.4 Projects expected to be completed to meet the 2012 peak demand 32 5.2.5 Projects expected to be completed to meet the 2013 peak demand 32
5.3 Summary 33
6. Existing and Planned Developments in Generation 39 6.1 Existing Generation 39 6.2 Planned Retirements of Existing Plant 43 6.3 Planned Future Generation (2009 – 2013) 43 6.4 Non-Contracted Generating Capacity 44 6.5 Interconnections 46 6.5.1 Interconnection with the UAE and the rest of the GCC Grid 46
7.1 System Demand 47 7.2 Demand Forecast 49 7.3 System Maximum Demand Forecast and Generation Availability 53
8. Transmission System Performance 58 8.1 Power Flow and Voltage Profiles 58 8.2 Fault Lvels 66
9. Development Opportunities 67
9.1 Review of the generation versus load balance on an area basis 67
9.2 Available grid station capacity 69
10. Derogations 76 Appendix A Review of Future Developments 80
A.1 Summery to projects to be completed annually between 2009-2013 peak demand 80 A.2 Projects expected to be completed to meet the 2009 peak demand 80
A.3 Projects expected to be completed to meet the 2010 peak demand 81
A.4 Projects expected to be completed to meet the 2011 peak demand 84
A.5 Projects expected to be completed to meet the 2012 peak demand 88
A.6 Projects expected to be completed to meet the 2013 peak demand 92
Appendix B Transmission System data 94
B.1 Substations Loads and Capacitor data 94 B.2 Overhead Line Circuit Capacities and Parameters 94
B.3 Transformer data 94
Appendix C Power System Studies 109
C.1 Summary of Load Flow Study results 109 C.2 Summary of Fault Level Study results 109
C.3 Diagrames of the model for the Load Flow Study Results 109
1.0 Executive Summary This Capability Statement presents the Oman Electricity Transmission Company’s development plans for the 220 kV and 132 kV transmission systems for the years 2009 to 2013.
The Statement includes data for the generators, loads, overhead line and cable circuits, transformers and capacitors used in the development of transmission system models for the power system studies undertaken with OETC’s DIgSILENT power system analysis software, version 14, in preparation of this Capability Statement. The Statement also includes the results of power system analysis of the transmission system that defines system performance when operating under the extremes of peak and minimum demand in each of the five years. From this analysis an assessment has been made of the opportunities for the connection of new generation and new demand on the system.
Table 1 lists the schedule for committed and planned system development projects on the 220/132 kV transmission system, although it should be noted that not all of the projects listed have full authorisation at this time. Implementation of these system development projects will increase the number of 220/132 kV grid stations from six to fourteen before the summer peak of 2013, with an additional installed firm grid substation capacity of 5,000 MVA. The number of 132/33 kV grid stations will also increase from the thirty one in service at the beginning of 2009 to forty nine (49) by the summer peak of 2013.
During the next five years the company is introducing direct voltage transformation from 220 kV to 33 kV and from 132 kV to 11 kV on the transmission system with respective 220/33 kV and 132/11 kV substations for the major residential/tourism developments at Blue City and Azaiba Coast (Wave Project).
It is also one of OETC’s strategic planning concepts to complete a 220 kV double circuit ring around northern Oman. By the summer of 2010 the proposed 220 kV connection between the Sohar Interconnector Station (SIS) and Al-Wasit in Mahadah will be completed to link the main load centre in Oman (Muscat) with the UAE and the rest of the GCC Grid via Sohar and the rapidly developing Sohar port and industrial area. By the first quarter of 2012 the 220 kV transmission system will also be extended from Misfah in the Muscat area to Jahloot and further eastwards to Sur. In addition, OETC plans to upgrade the line between Mahadah to Ibri to 220 kV to support the voltage and meet the expected load growth.
Beyond the period covered by this Statement, i.e. by the end of 2014, the 220 kV ring will be completed with the connection of Misfah Switching Station to Nizwa University Grid Station. The proposed 1,000 MW power plant at Duqum is scheduled for connection to the transmission system at some stage from 2015 onwards.
In accordance with Condition 27 of OETC’s Transmission Licence the power flow studies presented in this Capability Statement are based on demand forecast data provided by Oman Power and Water Procurement Company (OPWP) which it has used in its Seven-Year Statement (2009 – 2015). The forecast has been disaggregated by grid station, according to available DISCO data, for detailed power system analysis.
Table1 (continued): Summary of Planned Developments on OETC Transmission System (2009 - 2013)
Project No.
Description Status Details Purpose
Cont: 2010
5
132/33 kV GSP at Saham with 132 kV DCCT line from Khabourah and 220/132 kV SIS (Seh Al Makarim) grid station looped in and out of Saham
Under construction due in service Q3’09
2 x 125 MVA transformers Takes load transfer from Sohar Grid and Khabourah
6 220 kV DCCT line from Barka Power station to Filaj
Under construction, due in service Sep'09
11km, 220 kV DCCT line Reinforcement of OETC system between Barka P/Stn and Filaj
7 220/132/33 kV GSP at Airport Heights fed from the 220 kV Al Falaij - MSQ DCCT line
Under construction, due in service Nov.'09
2 x 500 MVA + 2 x 125 MVA transformers
Supplies new load and transfers some load from Bousher and Mawalleh
8 Azaiba Coast 132/11 kV grid station to supply Wave Project
Under construction, due in service Nov.'09 due to Airport Heights project
3x50MVA transformers Dedicated for the Wave project
9
Upgrade Seeb Main 132/33 kV grid station from 2 x 63 MVA transformers to 2 x 125 MVA. Upgrade 132kV DCCT overhead line from Mawalih to Seeb Main from single conductor to twin conductor
Evaluation of bids is ongoing.Expected
completion date is Q3’10 2 x 125 MVA transformers
Reinforcement of OETC system. Existing Seeb main grid is overloaded
Table1 (continued): Summary of Planned Developments on OETC Transmission System (2009 - 2013)
Project No.
Description Status Details Purpose
Cont:2010
16 Adding New transformer 125MVA at MSQ
Expected to be in Q2’10 1 x 125MVA Transformer
To meet N-1 for the existing grid. This transformer will be connected to the new 125MVA transformer at 2011 as MSQ-2 Grid within the same boundary of the existing grid.
17 Adding New transformer 125MVA at Mawalih grid.
Expected to be in Q2’10 1 x 125MVA Transformer
To meet N-1 for the existing grid. This transformer will be connected to the new 125MVA transformer at 2011 as Mawalih-2 Grid within the same boundary of the existing grid.
Table1 (continued): Summary of Planned Developments on OETC Transmission System (2009 - 2013) Project
No. Description Status Details Purpose
Peak 2012
35 132/33 kV GSP at Yankit connected to new 132 kV busbars at Jahloot grid station via 132 kV DCCT line
Expected to be in Q2'12 2 x 125 MVA transformers 45km 132 kV DCCT line
Phase 1 (2010): 60 MVA supplied at 132 kV from Yitti (5km away). Phase 2 (2011): With
220 kV established at Jahloot supply to Yankit taken from Yitti at 132 kV. Seefa Resort (15km from Yankit) supplied from Yankit. This project not confirmed waiting
conformation form the developer.
36 220/132 kV GSP at Jahloot connected to Misfah grid station via 220 kV DCCT line Expected to be in Q2'12 Adding 2 x 500MVA with 70km of 220kV
O/H line between Misfah and Jahloot
To meet load growth requirements and improve voltage profile and to be linked with
Sur area.
37 220/132 kV grid station at Sur connected to Jahloot grid station via a 220 kV DCCT line when 220 kV bus established at Jahloot
Expected to be in Q2'12 2 x 500 MVA transformers 160km 220 kV DCCT line
Required to support voltage in Sur and BB Ali areas. And to meet load growth ( OETC studying to construct this line as 400kV and
operated as 220kV)
38 Upgrade of Mudhabi grid station from 2 x 63 MVA to 2 x 125 MVA transformers Expected to be in Q2_12 2 x 125 MVA transformers To meet load growth requirements and to
maintain N-1
39 Upgrade of Izki grid station from 2 x 40 MVA to 2 x 125 MVA transformers Expected to be in Q2_12 2 x 125 MVA transformers To meet load growth requirements and to
maintain N-1
40 Upgrade of Rustaq grid station from 2 x 63 MVA to 2 x 125 MVA transformers Expected to be in Q2_12 2 x 125 MVA transformers To meet load growth requirements and to
maintain N-1
41 Upgrade of Sumail grid station from 2 x 63 MVA to 2 x 125 MVA Tx. Expected to be in Q2_12 2 x 125 MVA transformers To meet load growth requirements and to
maintain N-1
42 132/33 kV GSP at Al Kamil Expected to be in Q2_12 2 x 125 MVA transformers Load transfer and to met load growth requirements in the area.
43 132/33 kV GSP at Nizwa (University) Expected to be in Q2_12 2 x 125 MVA transformers connected to LILO of Izki - Nizwa 132kV lines.
Load transfer and to met load growth requirements in the area.
44 132/33 kV GSP at Al Roudha Expected to be in Q2_12 2 x 63MVA transformers connected to Al Modhabi through 40km 132kV lines.
To increase Voltage profile for the long 33kV lines (60km), Load transfer and to met load
growth requirements in the area.
45 Construction of new 220kV Grid station at Misfah Expected to be in Q212 New 220kV GIS interconnection Grid for
new IPP at Misfah To connect the new IPP to the Grid.
46 Upgrading of Ghoubrah 132kV Expected to be in Q2'12 2 x 125MVA Transformers To meet N-1 , cater load growth and to
connect the new IPP
47 Upgrading of Wadi Adai 220/132kV Expected to be in Q4'11 2 x 500MVA transformers, with 45km 220kV over head lines
To connect the new IPP from Barka and to support the Voltage at Muscat Grid Stations (Wadi Adai, Wadi Al Kabir and Al Falaj and to be as alternative supply for these Grids.
Table1 (continued): Summary of Planned Developments on OETC Transmission System (2009 - 2013) Project
No. Description Status Details Purpose
Peak 2013
59 New Grid station at Dreez Expected to be in Q1'13 2 x 63MVA, 30km 132kV lines from Ibri grid station.
To cater the load growth at Dreez area and to solve the issue of voltage drop, currently
this area is fed by two 33Kv feeders from Ibri grid/ load transfer(46.1MW)
60 New Grid Station at Al Khadh(Muscat) Expected to be in Q1'13 2 x 125MVA, 10km 132kV lines from Mawalih grid station
To cater the load growth at Mawalih and Mabailaha and load transfer with grids in this
area(Mawalih , Seeb Main and Mabailah)
61 Upgrading of Barka Main Expected to be in Q1'13 2 x 125MVA
To meet N-1 for the existing grid. These transformers will be connected with existing Barka main as new Barka Main-2 grid within the same boundary.
62 Upgrading of Manah-Nizwa 132kV lines Expected to be in Q1'13 Upgrading of the conductor (20km) This project to be organized with UPCo. 63 Upgrading of Mahadah Grid Station Expected to be in Q1'13 2 x 63MVA To meet N-1 for the existing grid.
64 Installing of Fault Current Limiters at Ghoubrah Expected to be in Q1'13 using latest technology To reduce short circuit Current effect in the area.
In order to model future system development as accurately as possible the distribution companies are required by the Grid Code to provide OETC with information that identifies their load transfer plans, including the load to be transferred, the timing and the grid stations involved, data that is also provided to OPWP for its own forecast of generation requirements. From the individual demand forecasts of the distribution companies, OETC has developed its own demand forecast for the transmission system as a whole, including the load transfers between grid stations that are then incorporated into the power system models for each year.
The forecast average annual growth in system demand of almost 12 % over the period 2009 –2013 drives many of the planned grid station reinforcements with a large portion of the additional demand supplied to the distribution companies through the 132/33 kV grid stations. To meet security of supply requirements and provide load relief to the heavier loaded grid stations it will be necessary to transfer excess load to the new or existing, but lightly-loaded grid stations. Comparison of the demand forecast with generation availability as defined in the OPWP Seven-Year Statement (2009-2015) shows a potential shortfall in generation capacity at system peak in 2010 and 2011. To meet the shortfall caused by planned plant retirements at Ghubrah and Wadi Jizzi it is assumed that power will be imported from direct customer generation. In addition the new generating capacity from Barka Phase-2 (SMN), Barka Phase-3 and Sohar Phase-2 will be required to meet future growth and avoid a further shortfall in generating capacity.
As the demand grows there is a greater need to extend the 220 kV transmission system so that bulk power is transmitted at this voltage rather than 132 kV in order to avoid overloads, improve voltages and reduce power losses. Consequently it is OETC’s objective to operate 220 kV as the main transmission voltage and use 132kV for sub-transmission and at some future date consider the introduction of 400 kV for the transmission of bulk power over long distances.
From Table 1 a total of 64 transmission projects are planned over a three year period, most of which are designed to increase the transmission system capacity so that it can meet future growth in demand and satisfy the security criteria. This is a major programme of capital investment in its infrastructure that will be spread across the whole network to improve transmission system performance across northern Oman and power system studies presented in this Statement confirm that the planned investment in 220 kV grid stations and transmission circuits will provide substantial spare capacity on the 220 kV transmission system to well beyond 2013.
The major technical issue identified in the studies was with high short-circuit fault levels on the 132 kV busbars at 4 grid stations in the Muscat area. The grid stations at Ghubrah, Bousher, Rusail and Madinat Sultan Qaboos (MSQ) were all shown in earlier studies (OETC Five Year Capability Statement 2008-2012) to have high 132 kV fault levels. Accordingly, OETC has taken appropriate remedial action to address this problem by implementing in the short–term, measures to split the 132 kV busbars at Rusail and Ghubrah.
In 2009, the 132 kV busbars were split at Rusail, but practical difficulties at Ghubrah prevented its implementation and the action to split the 132 kV busbars there has been postponed to be implemented later. Until then operating restrictions are being applied to avoid performing any works near switchgear at Ghubrah Power Station. Splitting the 132 kV busabrs at these power stations significantly reduces the fault level on the 132 kV transmission system in the Muscat area and temporarily solves the short circuit problem at zero cost.
In 2012 Rusail will no longer need splitting due to the network development and reconfiguration works completed to facilitate the addition of new IPPs, and therefore the Rusail busbars will be returned to normal operation. In 2013, with the completion of transmission system developments required to facilitate the introduction of new IWPP at Ghubrah, splitting of the busbars will no longer be required.
Load flow studies have confirmed that with the exception of the 132 kV bus-bars at Al Hail, the voltage levels across the transmission system can be maintained within the +/-10 % limits defined in the Grid Code. In the case of Al Hail, the 132/33 kV grid station is currently supplied via a single circuit line from Dank, but by the end of 2010 this will be upgraded to a double circuit connection
At Al Hail and at other remote locations, such as Sur at the eastern end of the transmission system, there is a strong case for the deployment of reactive compensation as a cost effective means of improving the system voltage. Similarly, with the demand in the Muscat area continuing to grow there are occasions when some grid stations in the Muscat area suffer reduced voltages at times of heavy load. To overcome this problem, Muscat Electricity Distribution Company (MEDC) have agreed to install new capacitor banks on the 33 kV busbars at Bousher, MSQ, Muttrah, Qurum, and Jahloot grid stations and studies presented in the report have confirmed that their addition by the summer of 2010 will produce a significant improvement in the voltage profile across the Muscat area.
Consequently, OETC has written to the distribution companies to request that they add more capacitor banks at the distribution voltage level to operate within the recommended power factor as an additional measure for improving system efficiency for the 2010 and 2011 system peaks.
The voltage problems experienced in the Al Dahirah area has led OETC to review its plans for system reinforcement to this area with the 220 kV system extended from Mahadah (Al Wasit) to Ibri, with Ibri scheduled upgraded before the 2011 peak. When this work is completed, the transmission system in this area will be fully compliant with the voltage requirements set by the Grid Code and the (N-1) security requirements set by Licence Condition 26.
OETC has floated a reactive power and voltage study in coordination with the distribution companies and a detailed study of the short circuit issue is also in progress to formulate long term plans for dealing with the fault level issue beyond 2013.
The Statement has reviewed the opportunities for the connection of new generation and new demand and identified those grid stations with substantial spare capacity where it should be possible to connect new demand to the system. A review of the balance between generation and demand has shown that the
construction of a new 500 MW power plant at Ghubrah in 2013 to supplement the existing generation at Ghubrah and the Barka Phase 2 and Phase 3 power plants will produce a generation surplus in the Greater Muscat area.
Section 2 of the Statement provides an introduction to the document, identifying the main related documentation and the key changes that have taken place on the transmission system since the previous issue of the Statement.
Section 3 identifies the technical requirements of the Grid Code and the Transmission Licence with specific attention to system voltage, frequency and security of supply.
Section 4 describes the main engineering standards used by OETC in its planning and design of the transmission system.
Section 5 describes the existing transmission system and summarises the planned developments in each year over the period 2009 to 2013.
Section 6 identifies the existing and planned developments in generation and describes the interconnections both inside Oman and internationally, i.e. PDO and the UAE respectively.
Section 7 presents the demand forecast and compares this with the generation capacity available.
Section 8 discusses transmission system performance and presents the results of load flow and short-circuits studies that show the performance of the transmission system at both peak and minimum demand in each year from 2009 to 2013.
Section 9 identifies the development opportunities for the connection of new demand and new generating plant to the transmission system.
Section 10 presents the areas of the network where network components will be operating above firm capacity during the period 2009 - 2013 and identifies the need for new or renewed derogations from application of the N-1 security criterion, as appropriate.
2. Introduction 2.1 Licence conditions, Codes and Standards
This Transmission System Five-Year Capability Statement covers the period 2009 – 2013 which has been prepared by the Oman Electricity Transmission Company S.A.O.C. (OETC) in accordance with the requirements set down under Licence Condition 27 of the Electricity Transmission and Dispatch Licence granted to the Company on 1 May 2005 by the Authority of Electricity Regulation (AER). The Licence has been granted under the powers invested in the Authority by Article (2) of the Law for the Regulation and Privatisation of the Electricity and Related Water Sector promulgated by Royal Decree 78/2004.
The purpose of the Statement is to provide up-to-date transmission system data for potential and existing users of the transmission system so they can identify those parts of the transmission system which offer the opportunity for future development. The Statement is required to be updated annually so that users and potential users of the transmission system are furnished with the latest information.
Potential users of the transmission system should be aware of the following main documents that influence the planning and future development of the transmission system infrastructure:
i) The Grid Code for the Sultanate of Oman.
ii) The Electricity Transmission and Dispatch Licence granted to OETC, notably Licence Condition 26, which defines the requirements for the Security Standards and the maintaining of an Efficient and Economic Transmission System.
iii) The approved Transmission Security Standards prepared in accordance with Condition 26 of OETC’s Transmission and Dispatch Licence.
iv) The Statement of Charges for Connection to the OETC Electricity Transmission System.
v) The Statement of Charges for the Use of the OETC Electricity Transmission System.
2.2 System Development since the 2008-2012 Statement
Since the issue of the previous Capability Statement, covering the period 2008 – 2012, the following projects have been completed and are currently being energized in time to meet 2009 system peak demand:
i. Construction of the 132/33 kV Manah to Adam double circuit overhead line and associated Grid Station at Adam.
ii. Upgrading of the 132/33 kV substations at Nizwa and Bahla. The works undertaken were for replacement of the two 63 MVA transformers at Nizwa grid station with two
125MVA transformers, and replacement of the two 40MVAtransformers at Bahla grid station with two 125MVA transformers.
The following projects are in the final stage and will be in service by the end of 2009.
i. Construction of the132/33kV grid station at Saham and the associated 132 kV transmission system.
ii. Installation of two 125 MVA transformers at Liwa Grid Station. The double circuit 132 kV Wadi Jizzi – Liwa - Shinas transmission line has been already energiesd.
iii. Installation of two 125 MVA transformers at the 220/132 kV Muladah Grid Station.
In addition to the transmission system developments, three new, large industrial customers have been connected directly to the transmission system in the Sohar area:
i. Shadeed Steel connected to the 220 kV SIA-A grid station.
ii. Aromatics industrial load has been connected to the same grid station at 132 kV.
iii. Sharq Steel connected to the 132 kV SIA-A grid station.
2.3 Improvements in the preparation of the Statement
Since the issue of the Transmission System Capability Statement for 2008 – 2012 there have been a number of improvements in the data and the power system modelling upon which the studies that are discussed in the Statement are based. The most significant of these are:
i. The Statement presents complete solutions of all problems reported in the previous Five Year Capability Statement (2008-2012). By the end of the period covered by the present Statement, problems of line and transformer loadings, voltage, and fault current issues will be completely removed.
ii. The OETC demand forecast is based on the data provided by OPWP and distribution companies which should make for a more accurate forecast.
iii. A review of power system model resulted in more appropriate settings being used for the transformers tap changers and the terminal voltages of generating units.
The improvements in the demand forecast and the power system modelling should result in similar improvements being achieved in the accuracy of the power system studies upon which network development planning is based.
3. Technical requirements for compliance with the Grid Code and Licence
In order to comply with Condition 26 of the Electricity Transmission and Dispatch Licence the transmission system must be planned, designed and operated to provide a secure, efficient and economic supply of electricity that is of an acceptable quality to its users.
Whilst Condition 26 specifically sets out the Security of Supply requirements, the most important characteristics that determine the quality of supply are frequency and voltage. The requirements for maintaining transmission system frequency and voltage within specified operating limits are set out in the Grid Code, and most clearly defined under conditions ASC4.1 and ASC4.2 respectively of the Ancillary Services Code.
Other issues that relate to the planning of an economic and cost effective transmission system that provides a voltage supply of acceptable quality, such as standardisation of equipment ratings, limitation of system losses, and the control and limitation of disturbing factors that affect the voltage waveform are covered by relevant Omani and/or International Standards.
3.1 System Frequency
In accordance with condition ASC4.1 of the Ancillary Services Code, OETC is required to maintain System Frequency within the following limits:
a) During normal operating conditions, the nominal system frequency of the transmission system shall be 50.00Hz and will be controlled normally between 49.95Hz and 50.05Hz.
b) During exceptional steady state conditions, frequency deviations will not exceed 49.90Hz to 50.10Hz unless disturbed circumstances prevail.
c) Under disturbed conditions, system frequency could rise transiently to 51.50 Hz or fall to 48.0 Hz, but not exceed these limits.
As ASC4.1 points out, the frequency of the total system is responsive to changes in the balance between the active power demand and total available generation capacity. OETC must therefore ensure that sufficient generation capacity and demand is available and connected to the system at all times to respond automatically to active power imbalances and correct any frequency change.
In accordance with condition ASC4.2 of the Ancillary Services Code, OETC is required to control system voltage within the following limits:
a) The voltage on the 220 kV and 132 kV parts of the Transmission System at each site with a user connection will remain within the limits of ±10% of the nominal voltage level.
b) The voltage on the 33 kV and 11 kV sides of transmission transformers at Connection Sites with Users will normally remain within the limits of ±6% of the nominal value unless abnormal conditions prevail.
During some system disturbances, such as where short circuits occur, the voltage could collapse transiently to zero at the point of fault until the fault is cleared.
Voltage regulation requires both active and reactive power flows across the transmission system to be carefully controlled. The physical characteristics of the plant on the transmission system also give rise to the generation and absorption of reactive power. Reactive power flows across the transmission system can give rise to substantial voltage differences and it is therefore necessary to maintain reactive power balances between sources of capacity and demand on a “zone” basis.
Unlike frequency, which is consistent across an interconnected transmission system, voltages at different points on an interconnected system are determined by the local sources of demand and capacity, by the prevailing network configuration and by the reactive power flows across the network.
The management of voltage requires control of reactive power and this can be provided by centrally dispatched generators, transformer tap-changers, by the connection of capacitor banks at 33 kV or below, or by means of static compensation.
3.3 Security of Supply
In accordance with Condition 26 of the OETC Transmission Licence the capacity of the Transmission System to transmit electricity shall not be reduced in the event that a single electric line, cable, transformer, circuit breaker and/or associated plant is not in service, provided that during a period in which such single electric line, cable, transformer, circuit breaker and/or associated plant is not in service. The operating voltage of the Transmission System may reduce to any level specified from time to time for such purposes in the Grid Code. In effect, the transmission system should be planned and operated to provide an (N-1) level for security of supply.
The Transmission System taken over by OETC in 2005 had several components that failed to meet the (N-1) criterion, and the Licence recognised that it might take two years, but at system peak 2012 and 2013 all grid stations and overhead lines will meet most of required standards and criteria to bring the whole system into full compliance. To date some of these out of firm situations have been addressed, but equally the steep growth in demand has caused further circuits / transformers to become out of firm. Section 10 summarizes the system grid condition.
In addition to the technical requirements of the Transmission Licence and the Grid Code, the principal electrical standards used by OETC in its planning and design of the 220 kV and 132 kV transmission systems are:
4.1 Oman Electrical Standard OES 11
The standard covers the topic “General Specifications for Electrical Materials and Equipment” and defines the worst case conditions for system design purposes by the following parameters:
a) maximum ambient temperature (50˚C)
b) maximum surface temperature for metal surfaces (80˚C)
c) altitude (between sea level and 30 metres above sea level)
d) maximum wind velocity (125km per hour)
e) average annual rainfall (100mm)
f) Maximum relative humidity (100%)
In determining the thermal rating of an overhead line conductor “still air” (i.e. a wind speed of 0.5km per hour) is used as this has the least cooling effect on the conductor. The standard also defines the design parameters for the 132 kV systems in terms of highest voltage (145 kV), design fault level (31.5 kA) and the requirement that the system be solidly earthed. Currently it does not specify corresponding figures for the 220 kV systems.
4.2 Oman Electrical Standard OES 25A and 25B
These standards define the requirements for aluminium conductor steel reinforced and aluminium alloy conductor overhead lines and aluminium alloy stranded conductor overhead lines.
4.3 Oman Electrical Standard OES 27
Volume 1 of the standard covers the design requirements for a 132/33 kV, 2 x 125 MVA substation with 132 kV gas insulated switchgear, including the 33 kV switchgear. Volume 2 covers similar requirements for the 132/33 kV, 2 x 63 MVA substation with 132 kV outdoor SF6 switchgear.
4.4 Oman Electrical Standard OES 32
The standard covers the design requirements for 132 kV double circuit overhead transmission lines with 400mm2 All Aluminium Alloy Twin Conductors (AAAC) on lattice steel towers that are deployed across much of the 132 kV transmission system.
4.5 Other Standards
In cases where an Omani Standard is not applicable it is usual OETC practice to adopt the appropriate IEC Standard. This particularly applies to the design of the 220 kV transmission systems.
The Oman Electricity Transmission Company is authorized to undertake all regulated activities of electricity transmission and dispatch in northern Oman at voltages of 132 kV and above. The existing transmission system has two operating voltages, i.e. 220 kV and 132 kV. It extends across the whole of northern Oman and interconnects bulk consumers and generators of electricity located in the Governorate of Muscat and in the regions of Batinah, Dhahirah, Dakhliyah and Sharquiya.
The transmission system was first established under the Ministry of Housing, Electricity and Water (MHEW) in 1983 and underwent rapid expansion during the 1990s. Consequently much of it has less than 15 years service experience. After the electrical sector was unbundled, the OETC took over the operation of the transmission system on 1 May 2005. The present OETC transmission system consists of:
686 circuit-km of 220 kV overhead transmission line
2837 circuit-km of 132 kV overhead transmission line
12 circuit-km of 220 kV underground cable
14 circuit-km of 132 kV underground cable
5630 MVA of 220/132 kV transformer capacity
6970 MVA of 132/33 kV transformer capacity
Two 220 kV interconnection grid stations
Two 220/132 kV grid stations
Four 220/132/33 kV grid stations
Thirty one 132/33 kV grid supply point substations
The transmission system is interconnected at 220 kV from Al Wasit grid station in Mahadah with the transmission system of the UAE and through this interconnection it will form part of the GCC Grid that links the electricity supply systems of Kuwait, Saudi Arabia, Bahrain, Qatar, the UAE and Oman. This should provide increased security of supply and benefits to the member countries in the form of cost savings from the sharing of reserve capacity and energy resources. The interconnector will be fully energised and brought into service when the Inter-Governmental agreement is signed.
The OETC transmission system is also interconnected with the PDO transmission network at 132 kV via a single circuit overhead line that runs between Nizwa on the OETC system and Nahda on the PDO system. Under normal conditions the power transfer across the interconnection is forecast to be negligible, but in the event of an emergency on either network the interconnection can facilitate a power transfer of up to 60 MW to address the shortfall. The energy transfer between OETC and PDO is managed such that annually the net energy transfer is around zero.
The transmission system is supplied with electricity generated from eight gas-based power stations located at Ghubrah, Rusail, Wadi Jizzi, Manah, Al Kamil, Barka AES & Barka SMN (phase 2) and Sohar.
In addition the transmission system may be supplied from direct customers, such as Sohar Aluminium and OMIFCO and some more additional generating units have been added at Barka. .
Three Distribution Licence holders, i.e. Muscat Electricity Distribution Company(MEDC), Mazoon Electricity Company (MZEC) and Majan Electricity Company (MJEC), take the bulk of the power transmitted through the main grid, from the 220/132/33 kV and 132/33 kV grid stations.
In addition to the three distribution companies, eleven large private customers are directly connected to the transmission system. Seven of these are connected to the transmission system in the Sohar Industrial Area. The existing private customers are:
220 kV Connections
i. Sohar Aluminium
ii. Shadeed
132 kV Connections
i. Sohar Industrial Estate
ii. Sharq Steel
iii. PDO
iv. OMCO
v. Aromatics
vi. Sohar Refinery
vii. OMIFCO
viii. Rusail Industrial Estate
The following new customers will be directly connected during the period covered by the Statement:
Zoom will be connected with the new 220kV Sur grid station in 2010.
VALE will be supplied via a single circuit connection to the existing SIA-1 substation, with the second circuit connected from the new 220kV SIA-2 station by the end of 2010.
The New Muscat International Airport (Ministry of Transport) will be connected to Airport Heights grid station by 2011.
In 2008 the system gross peak demand of 3,139 MW which occurred at 15:00 hours on 31 May, an increase of 13.2 % on the 2007 peak demand. During 2008, the energy imported to the system from connected generating plant was 14,017.1 GWh, whilst that exported to private customers and the distribution companies was 13,837.6 GWh, resulting in system energy losses of 179.5 GWh, which equates to an system energy loss of 1.3 %.
5.2 Future System Development Projects
The power system studies presented later in this Capability Statement and used to define the constraints and opportunities that exist on the transmission system over the next five years have been performed on the basis that the committed and planned development projects detailed in Appendix A and summarised below will proceed as planned and be completed to the current schedule.
5.2.1 Projects completed to meet the 2009 peak demand
A geo-schematic diagram of the existing transmission system in 2009 is shown in Figure 1. In section 2.2 of this Statement it was noted that a number of projects had been completed since the 2008 – 2012 Capability Statement was published and that the new works were being energised so that they were available to meet the peak demand in summer 2009. These projects will provide load relief to some of the heavily loaded grid stations and transmission circuits in addition to improving the voltage profile. The projects designed to meet the 2009 system demand include a new grid station at Adam, and the upgrading of the transformers capacity at Nizwa and Bahla.
5.2.2 Projects expected to be completed to meet the 2010 peak demand
Figure 2 shows in geo-schematic form the system development plan to meet the 2010 peak demand.
The new projects scheduled for completion in time to meet the summer peak demand in 2010 are at various stages of development and the major projects for which a consultant has been appointed for construction are:
i) 220/132/33kV Airport Heights grid station
ii) Azaiba Coast grid station (Wave project)
iii) New 132/33 kV grid stations at Wadi Sa’a, and Yitti.
iv) Construction of the132/33kV grid station at Saham and the associated 132 kV transmission system.
v) Installation of two 125 MVA transformers at Liwa Grid Station. The double circuit 132 kV Wadi Jizzi – Liwa - Shinas transmission line has been already energised.
vi) Installation of two 125 MVA transformers at the 220/132 kV Muladah Grid Station.
A number of grid stations cannot maintain (N-1) security of supply and additional transformer capacity is being provided to meet the 2010 peak at MSQ (125MVA), Ghubrah (40MVA), Bousher (125MVA),
Mawalih (125MVA) and Seeb Main (63MVA) until new grid stations are available to provide load relief in the future. At MSQ and Mawalih the third 125 MVA transformer installed in 2010 will be further reinforced in 2011 as part of the process to establish a second grid station within the boundary of each site. At Bousher, two 125 MVA transformers will be installed to meet peak 2010.
The replacement of overhead lines with underground cables in the Muscat area is also planned for completion in time for the 2010 peak.
5.2.3 Projects expected to be completed to meet the 2011 peak demand
Figure 3 shows in geo-schematic form the system development plan to meet the 2011 peak demand.
The major transmission system developments that are expected to come into service between the summers of 2010 and 2011 to meet the summer peak in 2011 are planned for the coastal areas to the east of Muscat. Other major projects scheduled for that period are a second 220/132 kV grid supply point in the Sohar Industrial Area (i.e. Sohar Industrial Area ‘B’), a new 220/33 kV grid station at Blue City, the new 220 kV double circuit line between SIS (Seh Al Makarim) and Mahadah (Al Wasit) grid stations and the upgrade of the 132 kV double circuit line between Mahadah (Al Wasit) and Buraimi. In addition, the 220 kV system will be extended into the Al Dahirah area by the construction of a new 220 kV 120 km double circuit overhead transmission line from Mahadah to Ibri, where a new 220/132 kV 2 x 500 MVA grid station will be established. This project will help in transferring the flow of the bulk electric power to the more efficient 220 kV system, thus improving the voltage profiles in this area, and reducing power losses. By summer 2011 the 132 kV single circuit connection between Dank and Al Hail will be upgraded to a double circuit connection. This work is a priority as it is required to meet the (N-1) security requirements and OETC is striving to advance the completion date for this project by combining it in the same tender as the project for upgrading the 132 kV line between Mahadah (Al Wasit) and Buraimi grid stations.
The other major project to be commissioned before the 2011 summer peak that has been floated for consultancy services is the construction of a new 132 kV 30 km double circuit overhead line from Jahloot to Quriyat, with a new 132/33 kV, 2 x 125 MVA grid station to be established at Quriyat.
5.2.4 Projects expected to be completed in time to meet the 2012 peak demand
In the Muscat area, the main development is the further reinforcement of transformer capacity at MSQ, Bousher and Mawalih. The addition of a fourth 125 MVA transformers will enable OETC to establish two grid stations on each site by converting the temporary transformers installed for 2010 into permanent fixtures. The new grid stations (i.e. MSQ-2, Bousher-2 and Mawalih-2) will provide load relief for each of the existing grid stations. These projects are expected to be completed to meet the 2012 peak demand.
Figure 4 shows in geo-schematic form the system development plan to meet the 2012 peak demand.
The main investment to meet the 2012 peak is in the extension of the 220 kV transmission system from Barka (i.e. Barka – 2) to Misfah and on to Wadi Adai where the grid station would be upgraded 220 kV. The 220 kV transmission system will be extended from Misfah to Jahloot and on to Sur, a total distance of approximately 300 km. To cater for future growth in demand, consideration is being given to constructing these lines for operation at 400 kV, but operating initially at 220kV. This option will be discussed with the consultant in due course.
The other major projects planned for completion before summer 2012 are the new 220/132 kV, 2 x 500 MVA grid stations to be established at Sur, Wadi Adai and Jahloot. The consultancy services for these projects have been floated and the work is in progress. The new IPPs at Barka and Sohar will be connected to the 220 kV transmission system through new 220 kV GIS substations at Barka (Barka-2) and Sohar (SPS-2). SPS-2 will be connected to SIS (Sohar Interconnector Station) at 220 kV via a double circuit connection over a distance of around 40 km. However, part of the route near the power station will have to be run underground because of expected difficulties in obtaining a right of way for another overhead line circuit. Other projects that are required to meet the 2012 peak are the construction of new 132/33 kV grid stations at Yankit, Al Amerat, Ghala, Nizwa University, Al-Kamil, Al-Roudah, Multaqa (Sohar area) Free Zone and Buraimi-2Further upgrading projects are also required at Mudaibi, Izki, Rustaq and Sumail.
5.2.5 Projects expected to be completed in time to meet the 2013 peak demand
Figure 5 shows in geo-schematic form the system arrangement to meet the 2013 peak demand. Major projects expected to be connected to the transmission system by summer 2013are construction of new 132/33 kV grid stations at Al Khaudh (Muscat), Barka Main - 2which is required to supply the Blue City demand and Dreez which will be connected to Ibri. Further upgrading is planned for the Manah - Nizwa 132kV lines and the Mahadah 132/33 kV transformers from 30MVA to 63MVA.
To address the fault level issues at Ghubrah power station a number of design options are under evaluation to determine the most appropriate long term solution for the site.
The ambitious nature of the development programme planned for the period 2009 - 2012 is recognised and for the purpose of this Statement a conservative view has therefore been taken for developments in 2013 on the assumption that some projects may suffer slippage due to unforeseen circumstances and completion that was planned for 2012 could slip into 2013.
5.3 Summary
Table 1 in the Executive Summary has summarised the development plans for the OETC Transmission System on a project by project basis at the time of this Statement. The table identifies the projects to which OETC are already committed and those projects that are considered likely to proceed.
The power system studies presented later in this Capability Statement to show the expected performance of the transmission system over the period 2009-2013 have been performed on the basis that the committed and planned development projects in Table 1 and detailed in Appendix A will proceed as planned and be completed on schedule. The system studies are used to identify areas of the transmission system where there are opportunities for connecting new demand and new generation and where constraints should be applied to further development.
6. Existing and Planned Developments in Generation
6.1 Existing generation
The OETC transmission system is supplied by eight gas-based power stations:
• Ghubrah, Rusail and Barka (AES & SMN) in the Muscat region (Muscat Electricity Distribution Company supply area).
• Sohar (Phase 1) and Wadi Jizzi in North Batinah (Majan Electricity Company supply area).
• Manah in Dakhilya region and Al Kamil in Sharqiyah region (Mazoon Electricity Company supply area).
The eight power stations are described briefly below:
a) Ghubrah Power and Desalination Plant
The initial development of Ghubrah Power Station started in 1976 and the installation of the power and desalination plant was accomplished in six phases, four of which included the commissioning of new generating units. The layout of the site is complex and is a mixture of thirteen gas turbines and four steam turbines of various ratings. The net generation capacity is approximately 481.6 MW. However, 500 MW of new generation is planned to be in service at Ghubrah in 2013. This will contribute to improving voltage levels in the Muscat area.
b) Rusail Power Station
Rusail Power Station is located in the Rusail Industrial Estate. The power station has eight Frame 9E gas turbines installed and operating in open-cycle. The gross site rating of the units varies from 81 MW to 96 MW. The units were installed progressively between 1984 and 2000. The net generation capacity of the power station is approximately 684 MW.
.
c) Wadi Jizzi Power Station
Wadi Jizzi Power Station comprises ten Frame 6B gas turbines (with gross site ratings in the range of 27.6 - 30.2 MW) and one Frame 5P gas turbine (17.8 MW gross site rating) where are all operating in open cycle. The units were installed progressively from 1982 and the net generation capacity is approximately 290 MW.
Manah Power Station is owned by the United Power Company and when commissioned in 1996 was the first Independent Power Project (IPP) to be built in Oman. The station comprises three GE PG6541B gas turbines (each site rated at 26.7 MW) and two GE PG9171E gas turbines (site ratings of 95 MW and 97 MW respectively). The net generation capacity is approximately 279 MW.
e) Al Kamil Power Station
Al Kamil Power Station is another IPP and was commissioned in 2002. The station comprises three GE PG9171E gas turbines (site rating 94 MW) operating in open cycle and the net generation capacity is approximately 282 MW.
f) Barka Power and Desalination Plant
There are two power stations in Barka:
1. The Barka Power and Desalination Plant was commissioned in 2003 by AES Barka and was developed as an Independent Water & Power Plant (IWPP). The power plant comprises two Ansaldo V94.2 gas turbines (manufactured under licence from Siemens) and a steam turbine operating in combined cycle. The net generation capacity is approximately 434 MW.
2. The new Barka SMN plant (Barka – Phase 2) is an Independent Water & Power Plant (IWPP) and is due to be commissioned in 2009. There will be three gas turbines of 131 MW capacity each and two steam turbine of 161 MW capacity each. The total expected net generation capacity is approximately 683 MW.
g) Sohar Power and Desalination Plant
Sohar Power and Desalination Plant was also developed as an IWPP by the Sohar Power Company. The plant consists of three Siemens V 94.2 gas turbines (Ansaldo Extraction Type), a steam turbine and four desalination units. The three gas turbines came into service during summer 2006. The net power plant capacity is 590 MW.
Table 2 lists on a yearly basis the existing and committed future generating capacity over the period 2009 - 2013. The table presents the gross and net maximum capacity for each generating unit at each power station and takes account of the desalination load where appropriate.
6.2 Planned Retirements of Existing Plant There are a number of planned retirements of the existing units in 2010 and further retirements are planned before 2012. The planned retirements are as follows:
a) Ghubrah Power and Desalination Plant
In 2010, it is planned to retire the existing units ST3 (8.3 MW) and GT4-9 (100.5 MW). Also, in 2013 ST4 (39.2 MW) and GT1-3 (51 MW) will be retired.
b) Wadi Jizzi Power Station
The two Frame 6B gas turbines and the Frame 5P gas turbine have had their retirement delayed until 2012, when the gross generation capacity at Wadi Jizzi will be reduced from 290 MW to 219 MW.
6.3 Planned future generation (2009 – 2013)
There are four main generation developments planned for the period 2009 to 2013:
a) Barka SMN (phase 2) Power Station (714 MW)
During 2008 three Siemens V 94.2 gas turbines (Ansaldo Extraction Type) were declared for early commissioning, this gave an additional 392 MW of gross generating capacity in the system. In addition two steam turbines are due in service to meet the 2009 peak with a gross generating capacity of 322 MW, giving a total gross generation capacity of 714 MW with desalination.
This generation is essential to minimize the shortfall in contracted generation and will also provide reactive power for voltage support during the summer 2009 period.
b) New IPP at Barka (phase 3) Power Station (650-750MW)
Due to the expected future shortfall in generation OPWP has instigated planning work for a third power plant at Barka. This independent power plant (IPP) will be designed to have a generating capacity of between 650MW and 750MW (final capacity dependent on the results of the OPWP tender evaluation). For the purposes of preparing this Capability Statement OETC has assumed that the lowest capacity of 650 MW is connected in order to represent the worst case scenario for the system as a whole, but is making plans to connect the larger capacity if that is selected. The generation development assumed at Barka-3 in the studies used in this Capability Statement are for the first stage development generating 375 MW in 2011 and second stage 275 MW in 2012. Barka - 3 is currently at the consultancy stage, with the total plant capacity and size of the individual units still to be decided.
c) New IPP at Sohar (phase 2) Power Station (650-750MW)
OPWP has also taken action to instigate planning work for a second power plant at Sohar where there is already a large industrial demand and projections of future load growth show that additional power generation is required in the area. The new IPP will be introduced in two stages, like Barka – 3. For the purposes of preparing this Capability Statement OETC has assumed that the lowest capacity of 650 MW
is connected in order to represent the worst case scenario for the system as a whole, but is making plans to connect the larger capacity if that is selected. The generation development assumed at Sohar-2 in the studies used in this Capability Statement are for the first stage increasing system generating capacity by 375MW in 2011 and second stage a further 275 MW in 2012. The project is currently at the consultancy services stage.
d) New Ghubrah IWPP
The first phase of a new combined cycle power plant with a nominal capacity of 500 MW is planned for 2013 at Ghubrah.
Table 3 summarises the net capacity of the additional future generating plant over the period 2009 to 2013 assumed in this Capability Statement. The table shows that an additional 1800 MW of generating capacity from these plants is planned to be in service before the 2013 peak.
Table 3: New Contracted and Planned Generating Capacity
6.4 Non-Contracted Generating Capacity There are a number of private industrial customers directly connected to the transmission system that either operate or plan to operate their own on-site generation. The largest generating plant among these is Sohar Aluminium, which may export up to 220 MW. In addition, the UAE interconnected system is expected to provide an import/export capacity of up to 300 MW in future.
The interconnected system and the private customer generating plants can with the customer’s agreement be made available to support the contracted generation under emergency conditions in order to avoid power cuts in northern Oman because of a shortfall in the contracted generation. These generators are termed “non-contracted” generating plants. Table 4 shows the non-contracted generating capacity
Table 4: Non-Contracted Generating Capacity.
Power Station Net Generating Capacity (MW)
2009 2010 2011 2012 2013
UAE Interconnector 170* 170* 300* 300* 300*
PDO 60 60 60 60 60
Sohar Aluminum 230 400 # 400 # 400 # 400 #
Sohar Refinery Company (SRC). 35 35 35 35 35
Oman Cement Company (OCC). 5 0 0 0 0
Oman Mining Company (OMCO). 20 20 20 20 20
Net Generation 520 685 815 815 815
*These values are provisional.
# Updated contact with OPWP
Table 5 summarises the Centrally Dispatched Net Generation Capacity available over the period 2008 – 2013, with the new generation at Barka Phase III, Sohar II and the new Ghubrah 500 MW plant in service with the planned retirement of generating units at Al Ghubrah and Wadi Al-Jizzi taken into account.
Table 5: Centrally Dispatched Generating Capacity on OETC Transmission System
Power Stations 2008 2009 2010 2011 2012 2013 Al-Ghubrah Power & Desalination Plant 475 509.6 398.9 398.9 398.9 308.8 Rusail Power Plant 684 684.4 684.4 684.4 684.4 684.4 Wadi Al-Jizzi Power Plant 288 290.2 290.2 290.2 219.5 219.5 Manah Power Plant 279 279.3 279.3 279.3 279.3 279.3 Al Kamil Power Plant 282 282.3 282.2 282.2 282.1 282.1 Barka I Power & Desalination Plant 434 459 459 459 459 459 Sohar I Power & Desalination Plant 585 621 621 621 621 621 Barka II Power & Desalination Plant 714 712 711 711 710 Barka III Power & Desalination Plant 375 650 650 Sohar II Power & Desalination Plant 375 650 650 New Al Ghubrah Power Plant 500
Total Generating Capacity (MW) 3027 3839.9 3727.2 4476.2 4955.5 5364.4 Retirements and Degradation - - -112.7 -113.7 -184.4 -274.5
6.5 Interconnections
6.5.1 Interconnection with the UAE and the rest of the GCC Grid The 220 kV transmission interconnection with the United Arab Emirates (UAE) was completed in the first quarter of 2007. The interconnection connects Mahadah Grid (Al Wasit) to Al Oha Grid Station in Al Ain in the UAE. However, contractual issues have to date prevented the interconnection from coming into service. Nevertheless it is reasonable to expect that these will be resolved and that the interconnection can provide power to Oman in the event of a possible shortfall in generation.
The interconnection is via a 220 kV double circuit overhead transmission line with twin “Arcuria” (2 x 700mm2) AAAC conductors per phase, with a conductor thermal rating of 2000 Amps (i.e. 762 MVA per circuit).
In the longer term the principal technical benefit to be obtained from connecting Oman to the GCC Grid is in a reduced spinning reserve requirement, which will be shared between the members of the GCC Grid. However, in the shorter term the interconnection will allow Oman to import power from the GCC Grid to meet any potential generation shortfall. An import capacity of up to 200 MW will be available from the GCC Grid according to OPWP in its Seven-Year Statement (2009-2015).
6.5.2 Interconnection with PDO
The OETC transmission system is interconnected with the transmission system of the Petroleum Development Oman (PDO) which provides electricity to its sites across the central region of Oman for the purpose of oil exploration and development. . The interconnection is made at 132 kV between Nizwa grid station on the OETC system and Nahda 132 kV substation on the PDO 132 kV network by a 67 km overhead line with a single “Elm” (175mm2 AAC) conductor per phase and a circuit rating of 357 Amp (i.e. 82 MVA). The over head line is owned by PDO. Under normal conditions the power transfer between the two networks is allowed to float around zero MW, with power transfers balanced out over a period. The interconnection essentially allows OETC and PDO to share spinning reserve and supply limited power to each other in emergency conditions on either system.
6.6 Economic Dispatch
The Load Dispatch Centre of OETC dispatches generation based on its availability as stated by the Generator on a day-ahead basis, and its price as listed by the Oman Power and Water Procurement Co. (OPWP).
Under circumstances where the system frequency is seen to stray outside the specified limits, LDC will issue dispatch instructions to Generators based on Merit Order to rectify the situation.
6.7 Spinning Reserve The Load Dispatch Centre strives to maintain a spinning reserve equal to the rating of the largest generating unit connected to the transmission system, namely the 220 MW steam turbine generators at Barka. This figure might be reviewed by OPWP after introducing the new IPPs at Barka and Sohar if a larger unit size is adopted.
7.1 System Demand Maximum demand usually occurs on the OETC transmission on a weekday in the months of June or July, during a period of particularly high temperature and humidity. The growth in air conditioning equipment in domestic and commercial premises in Oman has ensured that peak demand usually occurs during the afternoon. Figure 6 shows the 24-hour demand profile for the transmission system on the day of the 2008 system peak demand (i.e. 31 May 2008). The 2008 system peak demand of 3,139 MW was recorded at 15:00 hours by the OETC Load Dispatch Centre. The historic growth in system peak demand over the period (2003-2008) is shown in Table 6.
Figure 6: OETC System Load on 2008 Peak Day (31/5/2008)
Table 6: Historic growth in peak demand and transmission losses (2003 – 2008)
*estimated
2003 2004 2005 2006 2007 2008
System Max Demand (MW) based on gross demand 2232 2371 2495 2613 2773 3139
Annual growth rate based on gross demand (%) --- 6.2 5.2 4.7 6.1 13
System Max Demand (MW) based on net demand 2139 2294 2395 2505 2662 3033
Transmission System Losses (MW) at system peak 35 38* 40 37 40* 61
Transmission System Losses (%) 1.64 1.66 1.67 1.47 1.50 2.0
Minimum demand generally occurs on the transmission system during night-time in December/January when electricity consumption in all major load categories is reduced. In 2008 the system minimum demand was 586 MW and this occurred on 18 January 2008 at 04:00 AM. The 2008 system minimum demand was 18.67 % of the 2008 system peak demand. The 24-hour profile for the day of minimum demand is shown in Figure 7.
Figure 7: OETC System Load on 2008 Minimum Load Day (18/1/2008)
7.2 Demand Forecast
Under clause 3 of Condition 27 of the OETC Transmission and Dispatch Licence it is stated that:
“The Licensee shall, when preparing the Capability Statement …. ensure that the forecasts of electricity flows and loading on each part of the Transmission System are consistent with the prevailing electricity demand forecasts prepared and used by the OPWP for the purposes of the Statement of future capacity requirements required by Condition 5 of the OPWP licence”.
The OPWP demand forecast is based on data supplied to them by the three distribution companies (i.e. Muscat EDC, Mazoon EC and Majan EC) and includes demand forecasts for the major customers that are, or will be, directly connected to the OETC transmission system at either 220 kV or 132 kV in their respective supply areas. The distribution company forecasts are provided in terms of:
The forecasts supplied to OPWP relate to the totals for each distribution company and do not indicate how this load is allocated to the individual grid supply points. The forecast data provided to OPWP does, however, include major future connections and the cumulative increase in load over the seven-year period covered by the OPWP Statement. OPWP has then reviewed this data and taken a view as to the probability that the individual schemes will proceed and if so, the rate at which their load will develop. The outcome of this review is presented as the OPWP Demand Forecast in its Seven-Year Statement.
The OPWP Demand Forecast was therefore taken as the starting point for developing the demand forecast presented in this OETC Capability Statement. The OETC forecast, however, is required to identify the future demand at individual grid stations at the system peak for each year over the period 2009 to 2013, since this information is required for the power flow studies.
Analysis of the demand forecast data used by OPWP in developing its Seven-Year Statement (2008 – 2014) identified basic annual percentage rates of 5, 6 and 7 % respectively for the growth in peak demand (excluding major projects) in the Mazoon EC, Muscat EDC and Majan DC supply areas. These rates have been applied to the grid station demands in the respective supply areas as noted by the OETC Load Dispatch Centre at the 2008 system peak (i.e. on 31 May, 1500hours). The demand associated with major industrial and tourism projects as assessed by OPWP (with diversity taken into account) was then superimposed on to the steady growth in the basic demand to produce a basic forecast. Section 5 identified a number of new grid supply points that are scheduled to come into service to meet the summer peak demands from 2009 onwards. These gird stations will provide load relief to the more heavily loaded grid stations and in some cases supply new loads.
The distribution companies’ plans for load transfers from existing grid stations that are heavily loaded to new grid stations are one of the most important elements of the demand forecast. Table 7 summarises the load transfers adopted in the studies based on consideration of what is required and what OETC has considered viable. OETC, however, acknowledges that this aspect of the forecast needs to be improved in future and believes that it would be helpful if the distribution companies were to give greater consideration to feasible load transfers when planning their distribution networks, and to develop proposals for load transfers in coordination with OETC.
7.3 System Maximum Demand Forecast and Generation Availability Table 8 shows the grid station demand forecast for the period 2009 – 2013 with prospective load transfers taken into account and the forecast developed in accordance with the methodology described in sub-section 7.2.
Table 8: OETC Transmission System Demand Forecast by Grid Station
Grid Station Total Demand by Grid Station 2008 2009 2010 2011 2012 2013
Table 9 compares the total demand forecast with the available generating capacity from Table 5 and shows that with no additional non-contracted generating capacity connected and zero power import over the cross-border interconnection with the UAE, then there will be a shortfall in generating capacity in Oman in 2010, 2012 and 2013 should the planned retirements at Ghubrah and Wadi Jizzi go ahead as planned.
Table 9: Comparison of Demand Forecast with Available Generating Capacity including Planned Retirements
Power Stations 2008 2009 2010 2011 2012 2013 Al-Ghubrah Power & Desalination Plant 475 509.6 398.9 398.9 398.9 308.8 Rusail Power Plant 684 684.4 684.4 684.4 684.4 684.4 Wadi Al-Jizzi Power Plant 288 290.2 290.2 290.2 219.5 219.5 Manah Power Plant 279 279.3 279.3 279.3 279.3 279.3 Al Kamil Power Plant 282 282.3 282.2 282.2 282.1 282.1 Barka I Power & Desalination Plant 434 459 459 459 459 459 Sohar I Power & Desalination Plant 585 621 621 621 621 621 Barka II Power & Desalination Plant 714 712 711 711 710 Barka III Power & Desalination Plant 375 650 650 Sohar II Power & Desalination Plant 375 650 650 New Al Ghubrah Power Plant 500
Table 10 compares the total demand forecast with the available generating capacity from Table 5 and shows that with the non-contracted generating capacity connected, zero power import over the cross-border interconnection with the UAE, and the initial tranche of plant retirements at Ghubrah postponed to 2011.
The transmission system data used in the power system studies to determine the system performance over the period from 2009 to 2013 is presented in Appendix B of this document.
8.1 Power Flow and Voltage Profiles The extreme cases of maximum and minimum system demand are used to define the performance of the OETC transmission system when it is most heavily stressed. From the studies of these extreme conditions it is possible to identify where the system is strong and has capacity to spare and, conversely, where it is weak and will need strengthening before new connections could be considered. The peak demand case identifies where there is a risk of overloading, of operation above firm capacity, or of system voltages falling below the voltage limits as defined in the Grid Code.
The system data described and presented in Appendix B has been used in a series of load flow studies to establish the performance of the OETC transmission system at peak demand in each year from 2009 to 2013 inclusive. The studies were undertaken on the basis that all circuits and plant will be available at system peak in each of the five years and that the system will be developed in accordance with the plans described in Section 5 of the Statement. The studies also assume that the demand will grow in accordance with the Demand Forecast, which is consistent with that produced by the OPWP and distribution companies, and that sufficient generation will be available from both Contracted and Non-Contracted Generating Plants to meet each annual system peak as indicated in the OPWP latest 7 Year Statement (2009-2015).
Table 11 shows the generating plant power assumed to be in service at peak load in each year of the study from 2009 to 2013. Under peak load conditions it is assumed that capacitive support will be fully switched on, i.e. capacitor banks at 33 kV grid stations are raised to provide maximum reactive power and voltage support. In the studies the generator terminal voltage and generator-transformer taps are set to control the voltage on the transmission system at the target busbar to within the allowable limits.
A second series of load flow studies were undertaken with the transmission system supplying minimum demand. The minimum demand case identifies where there is a risk of the busbar voltages rising above the voltage limits defined in the Grid Code and where additional generation has to be operated to absorb excess reactive power, since there are no reactors connected to the system. In 2008 the system minimum demand was approximately 18% of peak demand and under this condition the generation has been reduced to a level that provides the necessary margin of reserve capacity that is consistent with the operational practices adopted by LDC to handle minimum load conditions.
Table 12 shows the generating plant assumed to be in service at minimum load in each year of the study. For 2009, real data are listed in the table. These actual values have been obtained from the LDC Daily Report of the 2009 minimum load which occurred on 17 January 2009. The total generation was 623 MW on that date. Under minimum load conditions it is assumed that all capacitor banks will be switched out.
The key results of the load flow and fault level studies on the OETC transmission system are presented in detail in Appendix C for each year over the period 2009 to 2013. System diagrams showing the results of the peak demand load flows have also been produced and are available in Appendix C.
The results include the following:
The Transformers percentage loading of all grid stations at system peak demand are as per Table C.1.
Available spare capacity at each grid station in relation to firm capacity at system peak demand can be seen in Table C.2. It should be noted that although spare MVA capacities are available at some individual grid stations, there is no guarantee that all can be exploited simultaneously. Lack of available generation and/or voltage level limits may restrict simultaneous utilization of all spare MVA capacities.
Percentage loading of each overhead line and underground cable in the transmission system at system peak demand is as per Table C.3.
Voltage profile at each 220 kV, 132 kV and 33 kV bus-bar at maximum and minimum load, Table C.4.
Annual transmission losses at peak demand are as shown Table C.5.
Maximum 3-phase and single-phase to earth short-circuit fault levels are as shown in Table C.6 and Table C.7 respectively.
The principal findings from the power system studies are:
Out of firm conditions
a) Two of the six existing 220/132 kV grid stations have large amounts of spare capacity available over the period from 2009 to 2013 to cope with future growth in demand. These are MIS and Sohar Industrial Port ‘A’ (SIA-1) grid stations. The six new 220 kV grid stations commissioned over the period 2009 – 2013 at Airport Heights, Jahloot, Sohar Industrial Port “B”, Ibri, Sur, and Wadi-Adai will substantially increase the amount of grid transformer capacity connected to the transmission system to facilitate further development of the power sector. The additional capacity will enable load transfers between grid stations to eliminate over-firm operation such as at MSQ and Mawilah.
b) The 132/33 kV grid stations show more constraints. For example, at the summer peak in 2009, only twelve out of thirty two grid stations are operating within their firm capacity, i.e. more than 60% of the grid stations will be operating above firm capacity. One of these, Seeb Main, is shown to be overloaded. Upgrading Seeb Main 132/33 kV grid station from 2 x 63 MVA to 2 x 125 MVA transformers is at the consultancy stage (evaluation of EPC tenders) and planned to be commissioned in the third quarter of 2010.
c) Implementation of the development projects described in Section 5 and the modest load transfer programme of Table 7 will restore the full system to (N-1) compliance by the end of the Statement period.
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a) Three-Phase Short Circuit Studies The maximum 3-Phase and Single-Phase short-circuit fault levels have been determined in accordance with IEC 60909 and as such the calculation excludes the contribution to fault level from sources at lower voltages, e.g. from induction motors connected at 11 kV or below. The method is valid and consistent with that followed by other transmission companies in the absence of data from the distribution companies for short-circuit back-feeds to the grid station 33 kV busbars. Table C.6 summarises the results of the 3-phase fault studies:
a) All of the 220 kV busbars have fault levels within the corresponding switchgear ratings over the period 2009-2013.
b) All the 132 kV buses, except Ghubrah in 2009, have fault levels within the corresponding switchgear ratings. However, by splitting the busbars for 2010 the fault level is reduced to within the switchgear rating.
c) The 3-phase short-circuit level at all 33 kV busbars except Rusail, does not exceed the switchgear rating. At Rusail the fault level marginally exceeds switchgear rating in 2009 and even less so in 2010.
b) Single-Phase Short Circuit Studies Table C.7 summarises the results of maximum single-phase short circuit studies for years 2009 to 2013:
a) In 2009 the single-phase fault levels at all buses on the transmission system are within the switchgear rating except at the Ghubrah and MSQ 132 kV busbars, due to delay in splitting Ghubrah busbars
b) In the years 2010 to 2013 the fault levels across the transmission system are within the corresponding switchgear short-circuit ratings. During 2010-2012 busbar splitting at Ghubrah (or MSQ) in addition to Rusail will be adopted. In 2013 fault current limiters will be installed at Ghubrah, thus limiting short-circuit currents to be within switchgear rating. This will provide a long-term permanent solution in the OETC Transmission System. In this case, there will be no need to apply the splitting technique at any busbars in the system. Both Rusail and Ghubrah Busbars will be operating normally without the need for splitting.
From the results of the load flow and fault level studies, and from analysis of the magnitude and location of generation and demand on the transmission system it is possible to give some indication as to where future generation and demand can be connected to the transmission system without causing or exacerbating any critical technical issues.
9.1 Review of the generation versus load balance on an area basis The performance of the transmission system is affected by the transfer of power, both real and reactive, from one region to another. Large power transfers between regions over long distances increase the voltage drop across the transmission system. They also increase the power losses and reduce the efficiency of the system. Ideally if the balance between generation and demand is maintained on a regional or area basis then power transfers over long distances can be minimised and the efficiency of the transmission system improved.
Figure 12 shows the connectivity of the OETC transmission in 2013 as it extends over the northern regions of Oman, a distance of around 500km from Shinas in the North West to JBB Ali in the south-east. To assess how generation and load is distributed over the transmission system the whole supply area has been split into seven geographic areas:
a) Central Muscat
b) Outer Muscat
c) North Coast
d) Sohar
e) Border and Interior
f) Nizwa
g) Sur.
The Central Muscat area, although geographically the smallest area, is by far the most heavily populated, with the highest demand and with the greatest amount of connected generation, even though much of the generation currently operating at Ghubrah is the oldest on the system and the most inefficient.
The Sohar area is rapidly developing around the new port with new industry seeking connections to the OETC transmission system or the distribution system of the Majan Electricity Company. Some of the larger industrial customers in this area also operate their own generating plant and on occasions supply power to the transmission system on a non-contracted basis.
The North Coast area covers the coastal strip between Barka on the western outskirts of the Muscat area and Sohar. This area is likely to develop as Sohar port grows, since the main road link between Muscat and Sohar runs through it. It also has been chosen for the Blue City Development which is a major residential and tourist development.
The Outer Muscat area is also being developed as a major tourism area along the coast just south of Muscat, with resorts being developed at Yitti and Yankit. However, the generation in Outer Muscat is located at Barka, around 140km from the resorts.
The transmission system in the Border area provides the interconnection with the UAE and supplies a number of grid stations that feed the Majan distribution system to supply a number of small towns and villages in this remote area. The power station at Wadi Jizzi is located in the north of the area and over 160km from the grid stations at Ibri and Al Hail where the voltage quality is poor. However, the development plan for the period 2009 – 2013 will see the extension of the 220 kV system from Al Wasit to Ibri and this should produce a marked improvement in the voltage quality.
The other areas, Nizwa and Sur, are provincial load centres that are exhibiting moderate growth. In both areas there is a local power station connected to the transmission system, and in the Sur area a private customer has installed generation that can provide support when required again on a non-contracted basis.
Table 13 compares the generation capacity installed in each of the seven areas with the forecast demand at the grid station at the annual system peak over the period 2009 to 2013. From the table it can be seen that there is a surplus of generating capacity in the Outer Muscat area across the period with the commissioning of Barka Phase 2 in 2009 and new IPP at Barka (Barka -3) in 2011/2012. The power balance in Central Muscat area is shown to be in deficit over the period from 2009 to 2013.
At Nizwa, the minor surplus in generation in 2009 becomes a deficit by 2011 as the demand grows From 2011 to 2013 there will be a modest, but increasing shortage of generation in the Nizwa area, so there may be a need for new generation in that area in future.
At Sohar a generation surplus is forecast to 2013 and the magnitude of the surplus suggests it could remain in surplus for some time after 2013. The load forecast shows there will continue to be high growth in industrial demand in the Sohar area.
The major power deficit on the transmission system is in the North Coastal area where it increases from 413 MW in summer 2009 peak to 709 MW in 2013. No generation is connected to the transmission system in this area, which stretches about 180km from east to west, and this area could obtain some benefit from generation at a central location.
The Border & Interior and the Sur areas will experience an increasing deficit in generating capacity over the period. By 2013, the deficiency in the two areas will be around 567 MW and 256 MW respectively. In the Interior the 132 kV transmission system experiences poor voltage levels at peak demand and new generation could provide the necessary voltage support, although reactive compensation would probably
be more cost effective. At Sur the voltage problems will be addressed by extending the 220 kV transmission systems from Jahloot to Sur in 2012.
9.2 Available grid station capacity Table C.2 in Appendix C identifies the available capacity at grid stations for the connection of new demand over the period 2009 to 2013.
Table 14 lists the grid stations where spare grid transformer capacity of more than 10 MVA is available1 to supply new demand, on the same area basis as that presented in sub-section 9.1. The MVA figure quoted refers to the available capacity in 2013.
1 The available capacity was determined in relation to the firm capacity of the substation.
The load flow studies summarised in Appendix C and discussed in Sections 8 and 9 of this Statement indicate a number of out-of firm grid stations and circuits in the early years of the Statement. In this final section we review each station / circuit which is currently failing to meet the N-1 criterion; we describe the development activities that OETC is undertaking or planning to undertake to address this non-compliance; and we indicate the expected time by which, in each instance, full N-1 compliance should be achieved.
It should be noted that the N-1 situation on the transmission system will change in future as demand on the system increases and as the system configuration changes. It is possible that further N-1 non-compliances might arise in the future until the overall system becomes substantially more robust through interconnection. OETC will keep this situation under review, and the non-compliance status will be updated in the 2010 Capability Statement.
As indicated in sections 8 and 9 and summarized in tables 15 and 16, there are some grid stations and overhead lines which do not comply with the N-1 criterion. The implicit derogations from the N-1 standard expired on 31st January 2009. It will be necessary therefore for a further location and duration specific derogations to be put in place by the Authority for each of the out of firm stations noted in table 15, and for each of the out of firm circuits noted in table 16.
The following points should be noted:
1- The loading values show in tables C1 and C3 (Appendix C), are those at the peak load conditions. The system peak lasts only for a period of less than one hour in one day during the relevant year. (For example refer to Figure 6 of 2008 daily load curve peak day.)
2- According to the most recent OPWP 7-year statement (2009-2015) which has been approved by AER, there are two forecast cases: (i) base case, and (ii) high case. The difference between the high and basic case in 2009 is 64 MW at the peak. This difference increases in the subsequent years and reaches 622 MW in 2013, indicating uncertainty in the forecast over the coming years especially with regards to new industrial loads. OETC supports OPWP’s view that the likelihood of the high case demands being realized is heavily dependent on the rate of recovery of the current global economic and financial conditions. OETC intends to monitor closely, in coordination with OPWP, the situation in order to assess the probability associated with the high case projection.
3- It is not prudent to invest in uncertain expansion. OETC will, of course, initiate new projects as new demand becomes more certain. Therefore, in Tables 15 and 16 we concentrate on covering N-1 conditions at the peak in 2009.
4- The modelling reflects all load transfer schemes that have been formally accepted by the relevant distribution company and included in their load forecasts. In addition, the modelling includes certain load transfer schemes, which are not yet confirmed by the distribution company concerned, but which
in the view of OETC are technically feasible and where no technical impediment to implementation exists.
OETC has adopted a three-fold approach to addressing these out of firm situations:
1) Reinforcement plans: strategic upgrading to add new circuits and/or to increase the capacity of grid stations within a minimum of two to five years. This will not just solve the problem; but it will also strengthen the transmission system for future development. This type of solution can only be applied as a longer term solution because of the time taken to implement. Reinforcement is the most robust long term solution for secure system development, but may not necessarily be the least cost solution to address the immediate out of firm conditions on the network.
2) Installing temporary transformers at heavily loaded grid stations, such as MSQ, Bousher, Mawalih, and Seeb Main. These will provide a temporary solution to the out-of-firm problems at the heavily loaded grid stations until a permanent solution is put in place.
3) Load Transfer: through agreement with distribution companies, load can be transferred from heavily loaded grid stations to more lightly loaded grid stations over the next three years. This would reduce the loading issues and balance the system during peak time. This is a mid-term solution which could be implemented with the cooperation of distribution companies in certain cases. Given the uncertainty of mid-term load forecasts in Oman at present, this is in some circumstances the most appropriate and economic action to address out of firm conditions on the network.
Tables 15 and 16 indicate a number of locations on the system where, at present, the out of firm condition of certain circuits or transformers is shown to exist to 2013 and possibly beyond. In respect of these currently unresolved out-of-firm conditions, OETC intends to hold further in-depth discussions with relevant system users, and particularly with the distribution companies, over the coming months to explore all possible options and to agree the most suitable option in each case. In this way, it is OETC's objective that the 2010 Capability Statement will forecast full resolution of the out-of-firm conditions by the end of the next Capability Statement period.
Table 15: Expected Over head lines/ cables which will not comply with N-1 criterion at peak demand in 2009
* This project was planned to upgrade the conductors but Government requirements may now mean that undergrounding is necessary. Await final government decision and review project if necessary.
No Send Bus Receive Bus
Voltage (kV)
No. of circuits
Circuit Type
Conductor Size/Type
Circuit length (km)
Circuit Rating (MVA)
Loading (%)
Indicative Date for full
Compliance against N-1
Proposed solution Mitigation
1 Barka Power Station 1-2 Filaj 220 2 OHL ARCURIA
x 2 11 762 67.55 End Q3 2009 Construction of new circuits 3 and 4
--
2 Al Wasit Buraimi 132 2 OHL ELM x1 33 82 70.31 End Q2 2011 Construction of new
double circuits with steel towers
--
3 Barka Main Filaj 132 2 OHL YEW x 2 9 261 66.19 Not firm by end Q4 2011
Construction of new circuit (circuit 3)
Load transfer by Discos
4 Dank Al Wasit 132 2 OHL 225 AAAC 81 89 51.00 End Q2 2011
Upgrading the conductors following splitting of the line and construction of
Wadi Sa’a grid station (In progress)
5 Manah Nizwa 132 2 OHL YEW x 2 20 261 59.89 Not firm by end Q4 2013
Design required for reinforcement project in coordination with UPC
6 Mawalih Seeb Main 132 2 OHL 240 ACSR 8 101 70.42 End Q2 2010 Replacement of the
Table 16: Expected Grid stations/ Transformers 132/33 kV which will not comply with N-1 criterion at peak demand in 2009.
No. Location
Total Transformer
Capacity (MVA)
Substation Firm
Capacity (MVA)
Loading (%)
Indicative Date for full Compliance against N-1 Proposed Solution Mitigation
1 Al Falaj 2 x 125 125 79.27 Not firm by end Q2 2011 Design required for increased capacity.
Load transfer by Disco from Falaj to Muttrah Grid Station
2 Barka Main 2 x 125 125 73.20 Not firm by end of Q4 2012 Design required for increased capacity
Load transfer by Disco to Nakhal
3 Bousher-A 2 x 125 125 97.53 Not firm by end of Q1 2012 Construction of Tx 3 and 4 (Bousher- B) plus options to be reviewed for further reinforcement
Load transfer by Disco to Bousher-B and Airport Heights
4 Dank 2 x 15 15 74.20 End Q4 2010 Upgrade of Dank by shifting Ibri transformer to Dank bringing capacity to 63MVA (In progress)
5 Ibri 2 x 63 63 89.21 End Q1 2011 Upgrade of Ibri to 125MVA ( In progress) 6 Izki 2 x 40 40 89.24 End Q2 2012 New upgrade of Izki
7 MSQ 2 x 125 125 83.98 End Q2 2010 40MW Load transfer by Disco to Qurum , plus options to be reviewed for further reinforcement
8 Mawaleh 2 x 125 125 77.22 End of Q2 2010 Load Transfer to Azaiba Coast under discussion with Disco , plus options to be reviewed for further reinforcement
9 Mudaibi 2 x 63 63 63.04 End Q2 2012 Upgrade of Mudaibi to 2x125MVA 10 Muladah 2 x 125 125 95.53 End Q1 2013 Add Tx 3 & Tx 4 Load transfer 11 Rustaq 2 x 63 63 82.00 End Q2 2012 Upgrade of Rustaq to 2 x 125 MVA transformers 12 Seeb Main 2 x 63 63 112.45 End Q2 2010 Upgrade of Seeb Main (In progress) 13 Shinas 2 x 63 63 65.41 End Q2 2010 Load transfer to Liwa GS
14 Sohar 2 x 125 125 80.65 Not firm by end of Q2 2012 Load transfer by Disco from Sohar to Liwa and Saham , plus options to be reviewed for further reinforcement
15 Sumail 2 x 63 63 66.85 Not firm by end of Q1 2012 Upgrade of Sumail to 2 x 125MVA planned but latest data from Disco indicates that this will not resolve non compliance. Requires review and possible redesign.
16 Wadi Adai 2 x 125 125 52.13 Not firm by end of Q2 2011 Load Transfer by Disco to new station at Qurum ( In progress)
17 Wadi Kabir 2 x 125 125 57.13 Not firm by end of Q12011 Load Transfer by Disco to new station Mutrah ( In
The OETC transmission network is undergoing widespread and rapid development due to the expansion requirements of distribution companies, large private customers, and new generation requirements based on the yearly demand growth and further reinforcements on the transmission network to ensure the security, quality and reliability of the system.
An important change to the Omani electricity sector is the new interconnector between Oman and the UAE (GCC link). The work on the interconnector was completed in the first quarter of 2008, but the circuits will not come into use until the GCC Intergovernmental Agreements are signed. A further development is the Mahadah to SIS interconnection through a 220kV double circuit. There are a significant number of projects required to meet the annual peak demands over the period of this Statement (2009-2013). These projects are considered below under the following categories:
• Projects of 2009 system peak.
• Projects that are at the tender evaluation stage prior to appointment of the preferred EPC Contractor.
• Projects for future developments which represent the least cost options to address problems with system growth, voltage profile, N-1 security criteria transmission system reinforcement.
The entire programme of ongoing and future projects which are planned for implementation over the period 2009 to 2013 are listed and described below. It should be noted that the project numbers referred to in the Appendix are identical to those in Table 1 of the Executive Summary, and it should also be noted that not all of the projects described have full authorisation at this time.
A.1 Projects of 2009 system peak
Project #1: 132/33 kV grid supply point at Adam
The project establishes at new 132/33 kV, 2 x 40 MVA grid supply point (GSP) at Adam in Dakhiliya Region which will be supplied directly from Manah Power Station via a 132 kV, 47 km double circuit overhead line. The new GSP will provide some load relief from Nizwa 132/33 kV GSP substation and will also greatly improve the voltage for Mazoon customers in Adam area, which are currently fed from Nizwa at 33 kV by around 70km to the north of Adam.
This project is in its final stage of construction and was completed on 10 June 2009.
Project #2: Upgrade of the transformer capacity at Nizwa and Bahla grid stations
The 132/33 kV grid stations at Nizwa (2 x 63 MVA) and Bahla (2 x 40 MVA) were both loaded above firm capacity at peak demand in 2008 and to address this situation both grid stations will have their existing transformers replaced with 2 x 125 MVA transformers. One 125MVA transformer at each grid station was energised in May 2009.
A.2 Projects expected to be completed to meet the 2010 peak demand
Project #3; 132/33 kV grid supply point at Muladah
The new 132/33kV, 2 x 125 MVA GSP at Muladha in South Batinah is being constructed on the same site as the MIS 220/132 kV interconnection grid station. One transformer at this new GSP station was energised on 11 April 2009. This GSP will provide load relief to the existing Muladha (11km from MIS) and Khabourah substations (53km from MIS).
Project #4: 132/33 kV grid supply point at Liwa
The new 132/33kV, 2 x 125 MVA GSP at Liwa in North Batinah provides load relief to both Shinas and Sohar grid stations. The project is completed in two phases. In the first phase the grid station was located at a point close to the existing 132 kV single circuit overhead line between Wadi Jizzi Power Station and Shinas. In the second phase, the existing single circuit line between Wadi Jizzi and Shinas was replaced with a new double circuit line. The project was energised on 20 June 2009.
Project #5: 132/33 kV grid station at Saham
The new 132/33kV, 2 x 125 MVA grid station is located near to the existing 132 kV double circuit line between the Khabourah 132/33 kV grid station and the 220/132 kV SIS (Seh Al Makarim) interconnector station and both circuits will be looped in and out of Saham. The new grid station will take load transfers from Sohar grid and Khabourah. This project should be completed in time by the third quarter of 2009 in order to meet 2010 peak demand.
Project #6: New 220 kV double circuit line between Barka Power Station and Filaij (circuits 3 and 4)
The capacity of the existing 220 kV double circuit line between Barka Power Station and Filaij 220/132 kV grid station needs to be reinforced in order to satisfy the N-1 security criterion when the Barka power station phase 2 development is commissioned in 2009. To reinforce the
connection a second 220 kV double circuit line between Barka Power Station and Filaij was scheduled to be commissioned at the end of 2009. The contract has been awarded and is in progress. This project has been delayed due to routing problems and a longer than expected delivery time for the 220 kV circuit breakers.
Project #7: New 220/132/33 kV grid supply point at Airport Heights
The new 220/132/33 kV grid station at Airport Heights is equipped with 220/132 kV, 2 x 500 MVA transformers and 132/33 kV, 2 x 125 MVA transformers. The grid station will supply new load and take load transfers from Bousher and Mawalih. The substation is located near the 220 kV double circuit line between Al Filaij and Madinat Sultan Qaboos (MSQ) which is looped in and out of Airport Heights. The work is scheduled for completion in the final quarter of 2009 (November 2009).
Project #8: New 132/11 kV grid station at Azaiba Coast
The new grid station at Azaiba Coast is dedicated to supply the electricity demand to the Wave Project and will be supplied from Airport Heights via two 132 kV, 10km underground cable circuits. The project is the first time direct transformation from 132 kV to 11 kV has been used on the OETC transmission system. Although the work is scheduled for completion in the second quarter of 2009 (May2009), the energization of Azaiba Coast is dependent upon Airport Heights grid station having already been commissioned. The indications are, however, that Airport Height may not be energised until November 2009.
Project #9: Upgrade of the 132/33 kV grid station at Seeb Main
The existing grid station with an installed transformer capacity of 2 x 63 MVA was loaded above its firm capacity during 2008 peak load conditions with each transformer loaded to 93 % of rating. The proposed scheme will see the existing transformers replaced with 2 x 125 MVA transformers. The existing 132 kV double circuit line to Seeb Main from Mawalih that was loaded at 59% of thermal rating will be upgraded from a single 240 mm2 ACSR conductor per phase to twin “Yew” AAAC conductors per phase, increasing the thermal rating of the overhead line from 101 MVA to 261 MVA per circuit. The work is scheduled for completion by the third quarter of 2010.
Project #10: 132/33 kV Grid Supply Point at Wadi Sa’a
The Al Buraimi Cement Factory has applied to the Majan Electricity Company for a connection to supply a demand of 20 MW in 2009 and a further 12 MW in 2010. To meet this requirement a new 132/33 kV, 2 x 63 MVA grid supply point is scheduled to come into service during the second quarter of 2010 at Wadi Sa’a, near Buraimi in the Dhahirah region. The cement factory is located around 40 km from Mahadah (Al Wasit) grid station and so to avoid voltage drop problems in this area the Wadi Sa’a grid station is being established.
• Project #11: 132/33 kV Grid Supply Point at Yitti
The new Yitti tourist resort in the Muscat Governorate will be supplied from a new 132/33kV, 2 x 125 MVA grid station at Yitti, which in turn will be fed from a new 132 kV bus-bar arrangement installed at Jahloot 132/33 kV grid station via a 132 kV double circuit line. The new GSP will also supply the existing Yitti load, which is currently supplied from Jahloot at 33 kV. The work is scheduled to be completed during the second quarter of 2010. The overhead line will be designed for operation at 220kV, but energized at 132kV. The 220 kV design makes provision for a possible future upgrade of the supply to 220 kV in the event that demand in the Yitti area grows to the extent that a higher transmission voltage is required to supply the area.
Project #12: Replacing portion of existing 220kV & 132kV OHL by Underground cables
near existing & planned residential Area in Muscat
Replacement of the existing 220kV & 132kV overhead lines with underground cables near existing and planned residential areas within the Muscat governorate is required for environmental reasons. When the transmission towers were established around fifteen years ago the Muscat area was not so heavily residential, but with urban development has come increased health and safety considerations. Undergrounding will also assist in eliminating or at least reducing the voltage drop issues that occur with overhead lines. The project is scheduled to be completed by the second quarter of 2010.
Project #13: Rusail-Mawalih 132kV
The Rusail-Bousher 132kV line will be disconnected from Bousher side and reconnected to Mawalih grid station. The existing line passes near Mawaleh at a distance of about 200 m. The project is expected to be in service by Q3 2010.
Project #14: Addition of new temporary 40 MVA transformer at Ghubrah
A new 132/33 kV 40 MVA transformer will be installed temporarily at Ghubrah by the second quarter of 2010 to support the existing 40MVA transformers by providing load relief of up to 30MW to meet N-1. The transformer will be in service until the capacity is upgraded to 2 x 125MVA to meet the 2012 peak.
Project #15: Addition of temporary 63 MVA transformer at Seeb Main
A 132/33 kV 63 MVA transformer will be installed temporarily at Seeb Main by the second quarter of 2010 to support the existing 63 MVA transformers by providing load relief of up to 30MW to meet N-1. As with Project #17, the transformer will be in service until the capacity is upgraded to 2 x 125MVA at some later date.
Project #16: Addition of third 132/33 kV 125MVA transformer at MSQ
A third 132/33 kV 125 MVA grid transformer will be installed at MSQ to shift around 60MW from the existing two transformers in order to meet N-1. The work is scheduled for completion in the second quarter of 2010.
Project #17: Addition of third 132/33 kV 125MVA transformer at Mawalih
A third 132/33 kV 125 MVA grid transformer will be by installed at Mawilah to shift around 60MW from the existing two transformers in order to meet N-1. The work is scheduled for completion in the second quarter of 2010.
A.3 Projects expected to be completed to meet the 2011 peak demand
Project #18: Bousher- Airport Heights 132kV
This project is linked with Project #14. The work requires the reconnection of 1.5 km of the 132kV double circuit line between Rusail and Bousher to become part of the new 132 kV Airport Heights – Bousher double circuit line. The connection of Bousher to Airport Heights rather than Rusail is required to satisfy N-1 and to limit short circuit fault level at Bousher and Rusail. The project is expected to be in service by the third quarter of 2010.
Project #19: Addition of fourth 125MVA transformer at Bousher Grid station The addition of a fourth 132/33 kV 125 MVA grid transformer at Bousher Grid will enable the 33 kV network at Bousher to be supplied from two groups of 2 x 125 MVA transformers, i.e. GT1/GT2 and GT3/GT4, effectively establishing two grid stations at Bousher (Bousher 1 and Bousher 2). This will enable OETC to share the load evenly between the two groups and enable each to meet N-1. It will also reduce the short circuit level at the 33kV busbars.
Project #20: New 132/33 kV Grid Supply Point at Quriyat
The demand at Quriyat is currently supplied at 33 kV from Jahloot, a distance of 30km, which causes reduced voltage during peak load conditions. The planned 132/33 kV 2 x 125 MVA grid station at Quriyat supplied from Jahloot via a 132 kV double circuit line will address the voltage problems around Quriyat. The work is scheduled to be completed by the second quarter of 2011. This project has been awarded for consultancy service.
Project #21: New 132/33kV grid supply point at Misfah and 132 kV connection
The new 132/33 kV 2 x 125 MVA grid station at Misfah is scheduled to come into service in the first quarter of 2011 to accept load transfers from Rusail, and meet future load growth and support the system voltage. The existing 132 kV Rusail – Wadi Adai double circuit line will be looped in and out of Misfah.
Project #22: Upgrade of the 132 kV connection between Dank and Al Hail
The existing connection to Al Hail is by a 132 kV 52km single circuit overhead line from Dank which is not compliant with the N-1 security requirements and therefore in contravention of Licence Condition 26. Al Hail also suffers the worst voltage conditions on the OETC transmission system because of its remote location on the system and its single circuit connection. Upgrading the connection to a double circuit is considered a high priority scheme and is required at the earliest date. OETC has taken action to that effect and as a result the work is scheduled for completion in the first quarter of 2011.
Project #23: New 132/33 kV grid supply point at Qurum
The new 132/33 kV, 2 x 125 MVA grid station is required to supply new developments in Ras Al Hamra and Qurum and to receive load transfers from MSQ and Wadi Adai grid stations. This project was planned to be in service by the 2009 summer peak, but due to difficulties in obtaining a suitable route and location for the substation the project has been delayed, with completion now scheduled for third quarter of 2010.
Project #24: Upgrade of the 132 kV double circuit line between Al Wasit and Buraimi
The existing 132 kV, 33 km double circuit line between Al Wasit and Buraimi was operating over-firm under 2008 peak load conditions, with each circuit loaded at 80% of thermal rating. To increase the capacity of the single ‘Elm’ conductor per phase to be replaced with twin ‘Yew’ conductor, but to carry the extra weight of the conductor the line will be rebuilt with steel lattice towers. Approximately 6km of the route will be by underground cable to avoid environmental impact and related health and safety issues, the cable size chosen to match the capacity of the upgraded conductor. The work is scheduled to be completed by the fourth quarter of 2010.
Project #25: 220 kV double circuit line between SIS (Seh Al Makarim) and Al Wasit
With the completion of this project, a double circuit 220 kV connection will be established across northern Oman from MSQ grid station in Muscat to the 220 kV interconnection with the UAE at Mahadah (Al Wasit). This will strengthen the network and improve the effectiveness of the cross-border interconnector. This work is scheduled to be completed during the third quarter of 2010. The EPC contract is awarded.
Project #26: New 220/33 kV grid supply point at Blue City
The electricity supply to the new Blue City development in the South Batinah region will be fed from a new 220/33 kV grid supply point connected between the MIS and Filayj grid stations by
routing the 220kV MIS – Filayj double circuit connection through the new grid station in a line-in-line-out (LILO) arrangement. The diversion will require two 220 kV double circuit overhead lines over part of the route and four 220 kV 2500mm2 cable circuits over the last 6 km of the route as it reaches the Blue City grid supply point. The project is dedicated to supply the Blue City project as requested by Mazoon Electricity Company and is currently in the design stage with the EPC tender ready to be floated when confirmation to proceed is received from Mazoon. At present the grid station is due in service during the first quarter of 2011.
Project #27: New 132/33 kV grid supply point at Muttrah:
A new 132/33 kV 2 x 125 MVA grid station is planned for Muttrah to take load transfers from Wadi Kabir and Al Falaj 132/33 kV grid stations. The new grid station will be supplied directly from Qurum 132/33 kV grid station (established under project #23) by construction of a new 132 kV double circuit line.
The Muttrah area is currently supplied from the existing Al Falaj and Wadi Kabir grid stations, which were both operating above firm capacity under 2008 peak load conditions. The work is scheduled to be completed during the fourth quarter of 2010.
The new grid station at Muttrah is preferred to the alternative of reinforcement of the existing Al Falaj and Wadi Kabir grid stations although it may be more complex and costly to undertake due to constraints on available building land due to the mountainous nature of the terrain.
Project #28: Second phase of development at Sohar Industrial Area 220/132 kV grid station:
This project is required in order to meet the expected industrial demand growth in Sohar industrial area. In addition this project will support and ensure that the existing Sohar Industrial Area 220/132/33 kV grid station which developed in the first phase meets the N-1 security requirements. This grid station is scheduled for the final quarter of 2010. This project was proposed to be 220kV/132kV/33kV but after confirmation from Majan, the grid will be constructed as 220kV/132kV system and it is designed to accept 33kV if required in the future. Currently there is one customer to be fed from this grid station, confirmed at around 90MW as a first stage, later rising to 170MW.
Project #29: Upgrade of 132/33/11 kV Grid Supply Point at Dank
The existing 2 x 15 MVA, 132/33 kV grid supply point at Dank in the Dhahirah region was loaded to 69 percent of its rating during the 2008 summer peak and further growth is likely to occur in 2009 above to the firm capacity during the 2009 summer peak. OETC recognises the need to increase the transformer capacity at Dank and is considering the options, with 2 x 63 MVA favoured, although 2 x 40 MVA or the installation of a third 15 MVA unit would offer a lower cost solution. The project completion date is expected during the fourth quarter of 2010.
Project #30: Adding new transformer 125MVA at MSQ Tx.4
This project will be done in addition to project # 16 where a fourth transformer will be installed at MSQ (MSQ-2) as part of the scope of this project. By this project MSQ-1 will meet N-1 and will be fine for the expected load in the area. This project is expected to be in service by Q2 2011.
Project #31: Adding new transformer 125MVA at Mawalih Tx.4
This project will be done in addition to project # 17 where a fourth transformer will be installed at Mawalih ( Mawalih-2) as part of the scope of this project. By this project Mawalih-1 will meet N-1 and will be fine for the expected load in the area. This project is expected to be in service by Q2 2011.
Project #32: Upgrade of Ibri grid station from 2 x 63MVA to 125MVA transformers
The existing 2 x 63 MVA, 132/33 kV grid supply point at Ibri in the Dhahirah region was overloaded during the 2008 summer peak. The favoured option for this project is to replace the two 63 MVA transformers with 2 x 125 MVA transformers. The award of the Consultancy Contract was done in last October 2008 and the project is scheduled to be completed by Q2 2010.
Project #33: Construct 132/33 kV grid station at Nakhal area with associated transmission system:
Construct 132/33kV Nakhal new grid stations and connect it with Al-Falij via 132kV lines. This project will assist with the new load growth in the area and also support the voltage. The load at Nakhal is now fed by two 33kV feeders from Barka main grid station which is fully loaded. This project will release load from Barka main. This project is expected to be completed by final quarter of 2010 and so will meet the peak of year 2011.
Project #34: Construction of new 220kV lines from Mahadah to Ibri:
This project was planned to be as 132kV system. OETC decided to build this project as 220kV to connect Al Dahirah grid stations with 220kV system due to shortage of reactive power and low voltage. This project will support the voltage in the area and it will meet the N-1 for all 132kV lines. The existing wooden lines will remain and the link between Wadi Sa’a and Dhank will be opened and used for emergency, and Dhank will be connected from Ibri. The existing lines can carry the required power to Dhank and Al Hail. This project would reinforce the transmission system voltage issues and further load demand in the area. By this connection the 220kV link will be ready for the completion on the ring around the four areas (Muscat, Batinah Dahira and Al
Dakhliah) through Misfah –Nizwa university 220kV system later on .This project is expected to be completed on second quarter of 2011 before the 2011 peak.
A.5 Projects expected to be completed in time to meet the 2012 peak demand:
Project #35: 132/33 kV grid supply point at Yankit:
The proposal to establish a 132/33 kV grid supply point at Yankit is in the early stages of development. The local load at Yankit is currently supplied at 33 kV from Jahloot, over a distance of 45km, which causes reduced voltages at peak load. However, with the introduction of Yitti 132/33 kV grid station, only 5km from Yankit, there is an option to receive a supply at either 132 kV or 33 kV from Yitti as a first phase in the development.
In the second phase, with the 220 kV system extended to Jahloot and a 132 kV GSP established at Yitti, a 132 kV double circuit line would be built to supply Yankit from Yitti. The proposed new resort at Seefa, only 15km from Yankit, would be supplied from Yankit at 33 kV. A number of options are still being considered by OETC before tender documents are finalised and issued for the appointment of a consultant. The project is expected to be completed by Q2’12. In addition confirmation of requirements has been requested from Muscat Distribution Company.
Project #36: 220/132 kV Grid Supply Point at Jahloot connected to Misfah Grid Station via
220kV DCCT line:
Extension of 220 kV transmission system from Misfah to Jahloot with a 220 kV, ≈ 100km double circuit line to the new grid station will eliminate voltage problems in the Jahloot area and strengthen the supply to this provincial expected load centre. The Existing Jahloot grid station will be connected to the proposed 220/132kV system by installing 2 x 500MVA transformers. This project will feed the Yitti and Quriat grid stations and the 220kV system will be extended to Sur. This project expected to be completed by the end of the second quarter of 2012.
Project #37: Construction of 220/132 kV Grid Supply Point at Sur:
Extension of 220 kV transmission system from Jahloot to Sur with a 220 kV, 160km double circuit line to the new grid station will eliminate voltage problems in the Sur area and strengthen the supply to this provincial load centre. The existing Sur grid station will be connected to the proposed 220/132kV system by installing 2 x 500MVA transformers. This project expected to be completed by the end of the second quarter of 2012.
This project is to upgrade the two transformers of Mudaibi grid stations from 63MVA to 125MVA. The project will have an impact on reducing the overloading on the grid stations and also will support the voltage in the area. This project is expected to be completed by second quarter of 2012.
Project #39: Upgrading Izki grid station:
This project is to upgrade the transformers at Izki grid stations from 40MVA to 125MVA which are owned by United Power Company. This project will address both overloading and voltage issues. This project is expected to be completed by second quarter of 2012.
Project #40: Upgrade of Rustaq grid station:
Upgrade of Rustaq grid station from 2x63MVA to 2x125MVA transformers. This will address the current overloading and voltages problems. The project is expected to be in service by second quarter of 2012.
Project #41: Upgrade of Sumail grid station:
Upgrade of Sumail grid station from 2x63MVA to 2x125MVA transformers. This will address the current overloading and voltages problems. The project will come to service by second quarter of 2012.
Project #42: Construction of new Al-Kamil grid station:
Construct a new 2x125MVA grid station. This is required to meet load growth in the Sharqiya area. The project is planned to come into service by the second quarter of 2012.
Project #43: Construction of new Nizwa University grid station:
Construct of a new 132/33kV GSP at Nizwa to meet the load requirement in the area. It will also facilitate the Duqm project, if that development proceeds. The project will be in by second quarter of 2012.
Project #44: Construction of new Al-Rawdah grid station:
Construction of 132/33kV GSP at Al-Rawdah is needed to meet the load growth requirement in the area. It will also improve the voltage profile. Currently this area is supplied from Mudaibi grid station via 33kV line of around 40km. The project is expected to be in service by second quarter of 2012.
Project #45: Construction of new 220kV grid station at Misfah:
This project will be constructed to connect the new IPP power at Barka this station will be connected to the proposed Barka-2 as interconnect grid for other links ( Wadi Adai, Jahloot and Nizwa University (Duqm project)). This grid will be connected through 220kV overhead lines 30km of high rating conductors to curry around 750MW and around 6km of 2500mm2 cables due to difficulties of rout between Barka and Filaj. The consultancy tender is in progress. This project expected to be in service Q1’2012.
Project #46: Upgrading of Ghoubrah 132/33kV grid station:
Currently this grid is 2 x 42MVA and not meeting N-1; the proposed new scheme will be 2 x 125MVA transformers with the GIS outside the Ghoubrah power plant area to connect the new proposed IPP for Ghoubrah. By construction of this project Ghoubrah will meet N-1 and accommodate the new growth in coastal area on Bousher. This project expected to be in serves by end of Q2 2012.
Project #47: Construction of new 220kV grid station at Wadi Adai:
This grid will be connected through 220kV overhead lines 45km from Misfah grid. The proposed grid will be connected to the existing 132/33kV grid at Wadi Adai. The route for this grid is high terrain. By construction of this grid all stressed 132kV lines between MSQ and Wadi Adai will be released and the voltage will be improved in the area. The consultancy tender is in progress. This project is expected to be in service by Q1’2012.
Project #48: Construction of new 220kV lines between SPS and SIS grid stations:
This project will be constructed to connect the new IPP power at Sohar by construction of 220kV over head lines 36km and around 6km underground cables these lines will be connected to the proposed Sohar-2 (SPS-2) as interconnect grid station. These lines will be designed as high rating conductors to carry around 750MW and. The consultancy tender is in progress. This project expected to be in service Q1’2012.
Project #49: Construction of new 220kV Grid at Barka(Barka-2)
This grid will be used for the new IPP at Barka (Phase-3). The grid will be as interconnection bus for the new IPP and for the new proposed 220kV lines which will be connected to Misfah. The proposed Bus will be connected to the existing through two bus section CBs and are kept open if all machines are running to avoid high short circuit effect on the existing grid, by using proper inter locking scheme. This project will be in line with Misfah and Wadi Adai projects. This project expected to be in service at Q1’2012.
Project #50: Construction of new 220kV Grid at Sohar (SPS-2)
This grid will be used for the new IPP at Sohar (Phase-2). The grid will be as interconnection bus for the new IPP and for the new proposed 220kV lines which will be connected to SIS. The proposed bus will be connected to the existing through two bus section CBs and kept open if all machines are running to avoid high short circuit effect on the existing grid, by using proper inter- locking scheme. This project will be in line with Misfah and Wadi Adai projects. This project expected to be in service at Q1’2012.
Project #51: New Grid Station at Al Amerat ( Muscat area)
This project will be as new grid 132/33kV with 2 x125MVA connected as LILO between MSQ-Jahloot 132kV lines. This grid will support the low voltage in Al Amerat area which currently fed from Jahloot. This grid will release load from Jahloot around 40MW and can be used to transfer load from Wadi Adai through three number of 33kV lines. The location of this grid will be finalized by MEDC. This project expected to be in service Q2’2012.
Project #52: New Grid station at Al Multaqa( Sohar area)
This project will be as new grid 132/33kV with 2 x125MVA connected to Sohar grid around 10km. This grid will relief load from Sohar Grid and to cater for load growth in the area.. The location of this grid will be finalized by Majan Company. This project expected to be in service Q2’2012.
Project #53: New Grid station at Al Ghala( Muscat area)
This project will be as new grid 132/33kV with 2 x125MVA connected to Airport Heights grid around 10km. This grid will release load from Bousher Grid and cater for load growth in the area. The location of this grid will be finalized by MEDC. This project expected to be in service Q2’2012.
Project #54: New Grid station at Al Buraimi
This project will be as new grid 132/33kV (Burimai-2) with 2 x125MVA connected to the lines between Mahadah and the existing Al Buraimi grid as LILO for an around 4km. This grid will release load from Buraimi Grid and to cater for load growth in the area.. The location of this grid will be finalized by Majan Co. This project is expected to be in service by Q2’2012.
Project #55: New Grid station at Sohar Economic Zone(SSEZ):
This project will be as new grid 132/33kV Free Zone with 2 x125MVA connected proposed SIA-2 grid station (220/132kV) around 7km underground cable from SIA-2. This grid will release load from Liwa Grid and cater for the load growth in the area. The location of this grid will be finalized by Majan Company. This project expected to be in service Q2’2012.
Project #56: New grid station at Al Aijah(Sur-2) 132/33kV:
This project will be connected to existing upgraded Sur grid station which includes the construction of a new 132kV/33kV grid station in the Al Aijah area to meet the new tourism load in the Ras Al Had area, and to support the voltage with 25km over head lines. Currently the load is supplied through 33kV lines of around 60km from the existing Sur grid station 132kV/33kV. This project is included in the price control as Sur-2 station, but after discussion with Mazoon Company, it has been decided to build new grid station in a location selected by Mazoon Company. The route survey has been started to save time and to assist in the selection of the proper location for this grid station. This project expected to be completed by the end of the second quarter of 2012.
Project #57: Adding 2 new 132kV lines between Barka Main and Filaj:
This project will be as new 132kV overhead lines( 3 and 4) connected between Filaj and Barka Main around 11km steel towers. By construction of these lines the other existing lines (1and 2) will meet N-1. This project expected to be in service Q2’2012.
Project #58: Upgrading of Wadi Adai Wadi Al Kabir 132kV lines:
These lines are constructed as single conductor which is not N-1. By construction of these lines the N-1 criteria will be met. This project expected to be in service Q2’2012.
A.6 Projects expected to be completed to meet the 2013 peak demand:
Project #59: New Grid station at Dreez:
New grid station will be constructed at Adreez area as 132/33 kV 2 x 63MVA transformers and it will be connected to Ibri grid station 30km on steel tower. This grid will support the low voltage in distribution system in the area and to release load from Ibri and Al Hail. This project expected to be in service at Q1’2013.
Project #60 New Grid station at Al Khoudh (Muscat):
New grid station will be constructed at Al Khoudh area Muscat) area as 132/33kV 2 x 125MVA transformers and it will be connected to Al Mawalih grid station 10km on steel tower/cable. This grid will release load from Mawalih and Seeb Main grid stations. This project expected to be in service at Q1’2013.
Project #61: Upgrading of Barka Main Grid station:
This project will be by adding two 125MVA transformers to the existing grid, which will be connected to the 132kV bus bar and the 33kV side will be as two groups to avoid short circuit and complication of the operation of these transformers. This grid will release load from Existing Barka Main grid. This project expected to be in service at Q1’2013.
Project #62: Upgrading of Manah Nizwa 132kV lines:
The existing lines are not N-1 , and these lines are owned by United Power Company(UPC), and need to be confirmed and addressed to them either by upgrading the conductor or by adding new circuits. This project expected to be in service at Q1’2003.
Project #63 Upgrading of Mahadah grid station:
The existing grid station is 30MVA it will be upgraded to 63MVA to meet the N-1 and to cater for the load growth in the area. Normally the growth in this area is very slow which can be overcome by using this capacity of transformers. This project expected to be in service by end of Q1’2013
Project #64: Installing of Fault Current Limiters at Ghoubrah
The short circuit current for the existing Goubrah grid station are more than the rated (26.2kA and 31.5kA). To address the fault level issues at Ghubrah power station a number of design options are under evaluation to determine the most appropriate long term solution for the site. OETC is looking seriously to add additional fault current limiter elements for each out going circuits. This option will be studied by third party to select the proper technology used and selecting the best to avoid any complication or any system stability problems which may will occur. By installing this equipment the short circuit current will be reduced on (Bousher and MSQ). This project expected to be in service by end of Q1’2013.
B.1 Substations Loads and Capacitor data. The grid station real and reactive power load at system peak demand for the period 2009 to 2013 and the respective reactive power support from capacitor banks connected at the grid station 33 kV busbars is shown in Table B.1.2 This data was used in the power flow studies of system peak demand presented in Section 8 of this Capability Statement.
B.2 Overhead Line Circuit Capacities and Parameters. The continuous thermal rating of a circuit is the maximum power flow that can be carried by that circuit on a continuous basis. The thermal rating of an overhead line is the power flow that can be carried by that line without infringing the statutory clearances and causing a risk to public safety and to the line itself. The thermal rating of an underground cable, however, is the maximum power flow that the cable can carry without either causing the cable to fail or to effectively reduce its projected lifespan through a deterioration of the cable insulation.
Although the thermal rating of an overhead line is affected by climatic conditions, for the purpose of assessing spare capacity on the transmission system the key climatic condition that limits the circuit rating is the summer rating when the temperature is at its highest and the solar radiation is at its peak. This also corresponds to when the electricity demand is at or near to its peak.
The circuit data presented in Table B.2 for the first year of the Statement period (2009) comprises the voltage, resistance, reactance, susceptance and thermal rating of the line and cable circuits. It also shows the circuit length and the type of overhead conductor or underground cable for each circuit.
Table B.3 shows the changes to the circuit data required in each of the other four years covered by the Statement.
B.3 Transformer data The data used to model the grid supply point transformers in the power flow studies of the 2009 summer peak demand condition is listed in Table B.4. The data comprises the transformer voltage ratio, the resistance and reactance, the tap range and step size. Table B.5 lists changes to the transformer data for the remaining four years of the Statement.
2 The 33 kV busbars at the grid supply points and the capacitors connected to them are owned and operated by the distribution companies.
C.1 Summary of Load Flow Study results The expected performance of the system at peak and minimum demand for each year from 2009 to 2013 are summarised in a series of tables and presented pictorially.
The study results are presented in the following tables: