OETC 2008 Approved Transmission Capability Statement[1]

Oman Electricity Transmission Company

Transmission Capability Statement (2008 - 2012)

March 2008

As Approved by AER - 6th April 2008

Five-Year Annual Transmission Capability Statement (2008 - 2012)

Contents

1. Executive Summary 1

2. Introduction 7

3. Technical requirements for compliance with the Grid Code and Licence 9 3.1 System Frequency 9 3.2 System Voltage 9 3.3 Security of Supply 10

4. OETC Design and Planning Standards 10 4.1 Oman Electrical Standard OES 11 11 4.2 Oman Electrical Standard OES 25A and 25B 11 4.3 Oman Electrical Standard OES 27 11 4.4 Oman Electrical Standard OES 32 11 4.5 Other Standards 11

5. The OETC Transmission System 12 5.1 The existing 220/132 kV transmission system 12 5.2 Future System Development Projects 13

5.2.1. Projects completed to meet 2008 peak demand 13 5.2.2. Projects expected to be completed in time to meet the 2009 peak demand14 5.2.3. Projects expected to be completed in time to meet the 2010 peak demand14 5.2.4. Projects expected to be completed in time to meet the 2011 peak demand15 5.2.5. Projects expected to be completed in time to meet the 2012 peak demand15

5.3. Summary 15 6. Existing and Planned Developments in Generation 24

6.1. Existing generation 24 6.2. Planned retirements of existing plant 26 6.3. Planned future generation (2008 – 2012) 27 6.4. Non-Contracted Generating Capacity 28 6.5. Interconnections 29

6.5.1. Interconnection with the UAE and the rest of the GCC Grid 29 6.5.2. Interconnection with PDO 30

6.6. Economic Dispatch 30 6.7. Spinning Reserve 30

7. Demand Forecast and Generation Availability 30 7.1. System Demand 30 7.2. Demand Forecast 32 7.3. System Maximum Demand Forecast and Generation Availability 34

8. Transmission System Performance 37


8.1. Power Flow and Voltage Profiles 37 8.2. Fault levels 41

9. Development Opportunities 42 9.1. Review of the generation versus load balance on an area basis 42 9.2. Available grid station capacity 44 A.1 Projects completed to meet 2008 peak demand 50 A.2 Projects expected to be completed in time to meet the 2009 peak demand 50 A.3 Projects expected to be completed in time to meet the 2010 peak demand 51 A.4 Projects expected to be completed in time to meet the 2011 peak demand 54 A.5 Projects expected to be completed in time to meet the 2012 peak demand 55

Appendix B Transmission System data 56 B.1 Substations Loads and Capacitor data 56 B.2 Overhead Line Circuit Capacities and Parameters 56 B.3 Transformer data 56

Appendix C Power System Studies 62 C.1 Summary of Load Flow Study results 62 C.2 Summary of Fault Level Study results 62 C.3 Soft Copies of load flow study results 62


Document History and Status

Revision Date issued Reviewed by Approved by Date approved Revision type

D.0 27 February 2008

RJ Fairbairn Draft

V.1 19 March 2008 RJ Fairbairn RJ Fairbairn 19 March 2008 Final

V.2 21 April 2008 C Whitaker Thani Al Khusaibi

21 April 2008 Final for Approval, incorporating AER 6.4.08 comments

Distribution of Copies

Revision Copy no Quantity Issued to

v.0 1 1 Thani Al Khusaibi

1 1 Punyabrata Sen

1 1 Derek Williams


1 1 Punyabrata Sen

1 1 Derek Williams


2 1 Punyabrata Sen

3 1 Derek Williams

Printed: 23 April 2008

Last saved: 23 April 2008 07:05 AM

Author: JB Gadsden

Project manager: RJ Fairbairn

Name of organisation: Oman Electricity Transmission Company S.A.O.C

Name of project: OETC Planning Function

Name of document: Five-Year Annual Transmission Capability Statement (2008 - 2012)

Document version: v.3 (Final as approved by AER)

Project number: UP00466


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1. Executive Summary This Capability Statement presents the Oman Electricity Transmission Company’s development plans for its 220 kV and 132 kV transmission systems for the years 2008 to 2012. The Statement includes power system analysis of the transmission system that defines its performance when operating under 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. The Statement also includes data for the generators, loads, overhead line and cable circuits, transformers and capacitors that has been used in the Digsilent power system analysis model.

Table 1 lists the schedule for committed and planned system development projects on the 220/132 kV transmission system. Implementation of these system development projects will increase the number of 220/132 kV grid stations from six to eleven before the summer peak of 2011, an additional installed firm substation capacity of 2,500 MVA. The number of 132/33 kV grid stations will increase from the thirty-one in service at the end of 2007 to forty-five by the summer peak of 2011. The 220/33 kV and 132/11 kV substations for the residential/tourism developments at Blue City and Azaiba Coast (Wave Project) are also part of the planned system development and these are the first substations of this type that OETC has plans to install on its transmission system. There are no planned developments identified yet for 2012.

The 220 kV transmission system will also be extended from Filayj to Jafnen by 2010 and then further eastwards to Jahloot and Sur by summer 2011. By summer 2010 the proposed 220 kV link between SIS and Al Wasit in Mahadah will complete the 220 kV connection from central Muscat, the main load centre, through Sohar the rapidly developing port and industrial area, to the UAE and the rest of the GCC Grid.

In accordance with Condition 27 of OETC’s Licence the power flow studies presented in this Capability Statement are based on demand forecast data provided by the Oman Power and Water Procurement Company (OPWP) and used by it in producing its Seven-Year Statement (2008 – 2014)1. The forecast has been disaggregated by grid station for detailed power system analysis.

1 At the time the demand data was collected the OPWP Seven-Year Statement (2008 – 2014) had not been published.


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The average forecast growth in system demand of almost 10 percent per annum over the period 2008 – 2012 drives many of the planned grid station reinforcements and a large portion


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of the additional demand will be supplied to the distribution companies through the 132/33 kV grid stations. To provide load relief to the heavier loaded grid stations it will be necessary to transfer excess load to the new or existing, lightly-loaded grid stations. In order to model future system development as accurately as possible it is necessary for the distribution companies to provide OETC with comprehensive load transfer information that identifies the load to be transferred, the timing and the grid stations affected. Regrettably, none of the distribution companies were able to supply this information and in its absence OETC has had to make its own estimate of load transfers at the grid stations.

Comparison of the demand forecast with the generation availability as defined in the most recent OPWP Seven-Year Statement (2007-2013) showed a potential shortfall in generation capacity at system peak in 2011 and 2012. In the Statement it has been assumed that to avoid the shortfall planned plant retirements at Ghubrah and Wadi Jizzi will be delayed until after 2012 and that power will be imported from private customer generation and via the UAE interconnector.

The power system studies2 have shown that the planned investment in the 220 kV grid stations and circuits will provide substantial spare capacity on the 220 kV system to well beyond 2012.

The major growth that is forecast in demand (i.e. an average annual growth rate of 9.9 percent) over the period 2008 to 2012 that is mainly spread along the coastal strip from Sohar to Quriyat has led to the proliferation of 132/33 kV grid stations across the transmission system. Whilst some of these supply new developments, others are required to provide load relief to existing substations that are operating above firm capacity. The outcome of this is that despite the major planned increase in 132/33 kV grid stations only a modest reduction in the number of those currently operating over-firm will be achieved by 2012.

The major technical issue that has been identified in the power system studies is with the 132 kV short-circuit fault levels in the Muscat area. The fault level studies have shown that the maximum 3-phase and single-phase fault levels on the 132 kV busbars at Rusail, Ghubrah, Boushar and MS Qaboos are above the 31.5 kA fault rating3 of the 132 kV switchgear. This does not necessarily mean that the switchgear is overstressed, since the individual circuit breakers will not be required to interrupt the total busbar fault current. OETC has confirmed that it switchgear at these sites can be operated within their individual breaker ratings, and will monitor the implications of fault level management on security of supply.

2 The power system studies used in the preparation of this Capability Statement were undertaken using transmission system models developed for that purpose with OETC’s Digsilent power system analysis software , version 13.2.337. 3 The switchgear fault rating and fault levels quoted in the report refer specifically to the symmetrical short-circuit breaking current , Ib as defined in IEC 60909 Part 0.


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The load flow studies have confirmed that with the exception of the 132 kV busbars at Al Hail, voltage levels across the transmission system can be maintained within the +/-10 percent limits defined in the Grid Code.

At Al Hail the 132/33 kV grid station is supplied via a single circuit line from Dank. This line is currently scheduled to be replaced before the 2011 peak with a new, higher rated double circuit line4. When this work is completed the transmission system 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 are looking prioritise this work so that the line can be reinforced before the summer peak of 2010.

At Al Hail and at other remote locations, such as at 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 and OETC is giving some consideration to this as an additional measure for improving system efficiency.

The Statement has reviewed the opportunities for the connection of new generation and new demand. The review has 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 installation of a new 400 MW generator at Ghubrah in 2012 to supplement the existing generation at Ghubrah and Barka Phase 1 and 2 power plants will produce a huge generation surplus in the Greater Muscat area. The surplus will have to be exported to other load centres and this will increase voltage drops and losses across the system. The concerns over fault level at Ghubrah and neighbouring grid stations suggest that unless the new plant is to replace the existing Ghubrah generation then it may be wise to consider an alternative area for its location. The north coastal strip between Muscat and Sohar is forecast to have a combined load of over 500 MW by 2012, but there is no generation along the strip and this may be a suitable area to locate the future generation.

This Statement is prepared annually by OETC in accordance with the terms of its Licence as a mark of good business practice and it is the intention that OETC will issue a half-yearly update for Users and Potential Users of the transmission system that will briefly report on progress and on any significant changes to the development plans.

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.

4 The existing 132 kV Dank – Al Hail single circuit line uses a single 225 AAAC conductor per phase (rated 502 A) and this will be replaced by a new 132 kV double circuit line with twin “yew” AAAC conductors per phase (rated at 1140 A per circuit).


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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 2008 to 2012.

Section 6 identifies the existing and planned developments in generation and describes the interconnections with the UAE and PDO.

Section 7 presents the demand forecast and compares this with the generation capacity available.

Section 8 presents the results of load flow and short-circuit studies that show the performance of the transmission system at both peak and minimum demand in each year from 2008 to 2012.

Section 9 identifies the development opportunities for the connection of new demand and new generating plant to the transmission system.


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2. Introduction This Transmission System Five-Year Capability Statement covering the period 2008 - 2012 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 having 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 users of the transmission system and to identify those parts of the transmission system which offer the opportunity for future development to existing and potential users of the system. 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

The major changes to the OETC Transmission System highlighted in this Statement compared with the transmission system as defined under the previous approved issue of the OETC Transmission System Capability Statement that covered the period 2006 – 2010, are:

1. Construction of the 220/132/33 kV Grid Station at Sohar Industrial Port Area connected to Sohar Power Station.

2. Construction of the 220/132 kV Sohar Interconnection Grid Station (SIS)


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3. Construction of the 220/132 kV Muladha Interconnection Grid Station (MIS)

4. Construction of a 220 kV (47km long) double circuit overhead line interconnection with the UAE. The line connects Al Wasit Grid Station with Al Oha Grid Station in Al Ain in the UAE.5

5. Installation of approximately 210km of 220 kV double circuit line to connect the new 220 kV grid stations to the existing grid

6. Construction of a new 132/33 kV, 2 x 63 MVA Grid Supply Point at Rustaq in the supply area of the Mazoon Electricity Company. The new substation is supplied from the existing 132/33 kV Muladha Grid Station via a new 132 kV double circuit overhead line, approximate length 30km.

7. Construction of a new 132/33 kV, 2 x 125 MVA Grid Supply Point at Mabella in the supply area of the Muscat Electricity Distribution Company. The substation was connected into the 132 kV transmission system between Rusail Power Station and Barka Main Grid Station.

5 This line has been commissioned, but will not be put into service until a final contractual agreement is signed.


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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 credible frequency change.

3.2 System Voltage In accordance with condition ASC4.2 of the Ancillary Services Code, OETC is required to control system voltage within the following limits:


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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 may 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 “zonal” 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, auto-generators, transformer tap-changers, by the connection of capacitor banks at 33 kV or below, or by means of synchronous or 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.

4. OETC Design and Planning Standards 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:


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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)6

e) average annual rainfall (100mm)

f) Maximum relative humidity (100%)

The standard also defines the design parameters for the 132 kV system in terms of highest voltage (145 kV), design fault level (31.5 kA) and the requirement that the system be solidly earthed. It does not specify corresponding figures for the 220 kV system.

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 system.

6 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.


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5. The OETC Transmission System

5.1 The existing 220/132 kV transmission system The Oman Electricity Transmission Company is authorized to undertake all regulated activities of electricity transmission and dispatch at voltages of 132 kV and above in northern Oman. 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 OETC transmission system was first established under the Ministry of Housing, Electricity and Water (MHEW) in 1983 and underwent rapid expansion during the 1990’s. Consequently much of it has less than 15 years service experience. The transmission system consists of:

576 circuit-km of 220 kV overhead transmission line

2,653 circuit-km of 132 kV overhead transmission line

8 circuit-km of 220 kV underground cable

14 circuit-km of 132 kV underground cable

3,630 MVA of 220/132 kV transformer capacity

3,233 MVA of 132/33 kV transformer capacity

Six 220/132 kV transmission substations

31 x 132/33 kV grid supply point substations

The transmission system is interconnected at 220 kV from Al Wasit 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 OETC transmission system is also interconnected with the PDO transmission network at 132 kV via a single circuit 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 negligible, but in the event of an emergency on either network the interconnection can facilitate a power transfer of up to around 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 seven gas-based power stations located at Ghubrah, Rusail, Waddi Jizzi, Manah, Al Kamil, Barka and Sohar.


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The three Distribution Licence holders, i.e. Muscat Electricity Distribution Company, Mazoon Electricity Company and Majan Electricity Company, take the bulk of the power transmitted through the transmission system through the 220/132/33 kV and 132/33 kV grid stations. In addition to the distribution companies four large private customers are directly connected to the transmission system7. Three of these and two others which will soon be connected to the transmission system are located in the Sohar Industrial Area, whilst the other (OMIFCO) is connected at the other end of the system at Sur. The existing private customers are:

a) Sohar Aluminium, which is directly connected at 220 kV

b) Sharq, Sohar Refinery, and OMIFCO which are directly connected at 132 kV.

In 2007 the system gross peak demand of 2,773 MW occurred at 1500 hours on 15 July, which was an increase of 6.3 percent on the 2006 peak demand. The corresponding net peak demand in 2007 was 2,662 MW and the system losses were estimated at 20 MW. During 2007, the energy imported to the system from connected generating plant was 12,372 GWh, whilst that exported to private customers and the distribution companies was 11,401 GWh, resulting in system losses of 971 GWh, which equates to an system energy loss of 8.5 percent. The total energy loss figure in percentage terms for 2007 is heavily influenced by those incurred during low load periods in the first quarter of the year.

A geo-schematic diagram of the existing transmission system as at 1 January 2008 is shown in Figure 1.

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 2008 peak demand A review of the list of major development projects that were underway on the OETC transmission system at the start of 2008 has confirmed that none of these will be available for service before the 2008 peak demand is reached in June/July 2008. Of those projects completed during 2007, the only major development that is yet to impact on the transmission system is the 220 kV cross-border interconnection between Al Wasit grid station (Muhadah) in north-west Oman and Al Oha grid station (Al Ain) in the UAE. The work on the interconnection was completed in the first quarter of 2007, but it is understood that agreement has still to be reached between the various parties with regard to the actual bilateral

7 Two other large customers, Shadeed and Aromatics, have still to be connected to the transmission system. Shadeed will be connected at 220 kV and Aromatics at 132 kV.


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Government arrangements and until an agreement is reached then the interconnection will not be switched into service.

The geo-schematic diagram of the system configuration in Figure 1 can therefore also be regarded as the system arrangement when meeting the 2008 peak demand.

5.2.2. Projects expected to be completed in time to meet the 2009 peak demand The project review, mentioned in sub-section 5.2.1, identified a number of projects that are scheduled to be in service to meet the summer peak of 2009. These projects fall into two distinct categories:

a) Projects already under construction and due in service before the end of the second quarter of 2009. These include the new grid stations at Adam, Liwa, Muladha (MIS), Airport Heights and Azaiba Coast.

b) Projects that are at the tender evaluation stage, prior to appointment of the preferred Contractor, and expected to be completed in time to meet the summer 2009 peak demand. These include the new grid station at Saham, the upgrading of the transformer capacity at Nizwa and Bahla, and reinforcement of the existing 220 kV double circuit line with a second double circuit line between Barka Power Station and Filayj grid station.

Figure 2 shows in geo-schematic form the system arrangement with all of the above schemes in service when meeting the 2009 peak demand.

5.2.3. Projects expected to be completed in time to meet the 2010 peak demand Whilst the projects required to meet the 2009 peak are well advanced the projects that are in the pipeline to meet the summer peak demand in 2010 are, as may be expected, much less advanced, with some projects at the consultancy stage, others about to enter that stage and the rest still at an early planning stage, with OETC not yet committed to the final scheme.

Those projects for which a consultant has been appointed are for the construction of a second 220/132/33 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 and new 132/33 kV grid stations at Wadi Sa’a and Yitti. Consultants have also been appointed for the construction of a new 220 kV double circuit line between SIS (Seh Al Makarim) and Al Wasit grid stations and the upgrade of the 132 kV double circuit line between Al Wasit and Buraimi.

The other projects for which consultancy contracts are yet to be awarded are for a new 220/132 kV grid supply point in the Jafnen Area, and new 132/33 kV grid stations at Muttrah, Qurum, Yankit and Shinas 2 (i.e. Shinas Resort). Other projects that are still on schedule to be completed before the summer 2010 peak are schemes to upgrade the transformer capacity at Seeb Main, Ibri and Dank.


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Figure 3 shows in geo-schematic form the system arrangement with all of the schemes in service when meeting the 2010 peak demand.

5.2.4. Projects expected to be completed in time to meet the 2011 peak demand The major transmission system developments that are expected to come on-stream 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. The main investment is linked to extension of the 220 kV transmission system from Jafnain to Jahloot and eastwards to Sur, a total distance of approximately 225km, with new 220/132 kV, 2 x 500 MVA grid stations established at Jahloot and Sur.

Of the projects scheduled to come on-stream in time to meet the 2011 peak demand the upgrade of the 132 kV single circuit connection between Dank and Al Hail to a double circuit connection is a priority as it is required to meet the (N-1) security requirements and thereby avoid a violation of Licence Condition 26. An early completion of this project is essential and OETC is therefore endeavouring to advance the completion date for this project.

The other major project that is still under consideration and due to be commissioned before the 2011 summer peak is the construction of a new 132/33 kV, 2 x 125 MVA grid station at Quriyat

Of the other projects initially identified by OETC, Dreez grid station is unlikely to be required if Ibri is upgraded and upgrading of the Al Wasit - Dank, and Ibri - Dank 132 kV double circuit lines are considered by OETC as low priority projects at this stage and have been excluded for further consideration in this Statement.

Figure 4 shows in geo-schematic form the system arrangement when meeting the 2011 peak demand.

5.2.5. Projects expected to be completed in time to meet the 2012 peak demand There are currently no new projects scheduled to come into service between the summer peaks of 2011 and 2012. The development programme between 2008 and 2011 is ambitious and the final year covered by OETC is seeking to expedite the completion of its projects. However, for the purpose of this Statement a pessimistic view has been taken and the final year covered has been designated at this stage for completion of any works that may over-run in 2011.

Figure 5 shows in geo-schematic form the system arrangement when meeting the 2012 peak demand.

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 this Statement was produced. The table identified the projects to which OETC are already committed and those projects that


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it is considered will proceed. The table eliminates a few that are considered unnecessary or of low priority and unlikely to be implemented in the years 2008 to 2012.

The power system studies presented later in this Capability Statement that show the expected performance of the transmission system over the period 2008-2012 have been performed on the basis that the committed and planned development projects summarised above and detailed in Appendix A will proceed as planned and be completed on schedule. The studies are used to identify areas of the transmission system where there are opportunities for connecting new demand and new generation. They also are used to identify areas where constraints should be applied to development. Delays to the development projects will reduce the available capacity and limit the opportunities at the affected locations.


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6. Existing and Planned Developments in Generation

6.1. Existing generation

The OETC transmission system is supplied by seven gas-based power stations: Ghubrah, Rusail and Barka in the Muscat region (Muscat EDC supply area)

Sohar and Waddi Jizzi in North Batinah (Majan EC supply area)

,Manah in Dakhilya region and Al Kamil in Sharqiyah region (Mazoon EC supply area)

The seven power stations are described briefly below: a) Rusail Power Station

Rusail Power Station is located on the Rusail Industrial Estate. The power station has eight Frame 9E gas turbines installed, 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. b) Ghubrah Power and Desalination Plant

The initial development of Ghubrah Power Station started in 1976 and 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 475 MW. c) Barka Power and Desalination Plant

Barka Power and Desalination Plant was commissioned in 2003 and was developed as an Independent Power Plant (IWPP). The power plant comprises two Ansaldo V94.2 gas turbines (manufactured under licence from Siemens) operating in combined cycle and a steam turbine. The net generation capacity is approximately 434 MW.

d) 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 585 MW.

e) Waddi Jizzi Power Station

Waddi Jizzi Power Station comprises ten Frame 6B gas turbines (with gross site ratings in the range 27.6 - 30.2 MW) and one Frame 5P gas turbines (17.8 MW gross site rating), all operating in open cycle. The units were installed progressively from 1982 and the net generation capacity is approximately 288 MW.

f) Manah Power Station

Manah Power Station is owned by the United Power Company and when commissioned in 1996 was the first IPP to be built in Oman. The station comprises three GE PG6541B gas


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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. g) Al Kamil Power Station

Al Kamil Power Station is another IPP. 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.

Table 2 lists the individual generating units on the existing system and their sent out capacity.


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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. However, the margin between generation and demand


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may dictate the need for these retirements to be delayed. The planned retirements are as follows:

a) Ghubrah Power and Desalination Plant

By 2010 two of the four existing steam turbines and nine of the thirteen existing gas turbines are due to be retired, so that the gross generating capacity at Ghubrah will be reduced to 282 MW, which amounts to a shutting down of 193 MW of existing plant.

b) Waddi 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 281 MW to 219 MW.

6.3. Planned future generation (2008 – 2012)

There are two main generation developments planned for the period 2008 to 2012:

a) Barka Phase 2 Power Station

By summer 2008 three Siemens V 94.2 gas turbines (Ansaldo Extraction Type) will have been installed, giving a gross generation capacity at the new power station of 363 MW. By summer 2009 three new steam turbines will be added, one for each of the Phase 2 gas turbines, so that the gross generation capacity will be increased to 677 MW.

b) New Ghubrah IWPP

The first phase of a new combined cycle plant is planned for 2012 at Ghubrah, with a nominal capacity at this stage of 400 MW. The actual composition of the units has yet to be decided.

Table 3 summarises the net capacity of the planned future generating plant over the period 2008 to 2012. The table shows that an additional 1,077 MW of generating capacity from these plants is planned to be in service before the 2012 peak.


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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 amongst these is the new plant that is being developed by Sohar Aluminium with an installed generating capacity of 180 MW. In addition, the UAE interconnector is expected to provide an import/export capacity of up to 200 MW.

The interconnector 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. Some of the plant that has been identified as being retired at Ghubrah and Wadi Jizzi in Table 2 is listed as Non-Contracted Generation in Table 4.

Table 5 summarises the Net Centrally Dispatched Generation Capacity available over the period 2008 – 2012, with the new generation for Barka Phase II and the new Ghubrah plant in service and the planned retirement of generating units at Al Ghubrah and Wadi Al-Jizzi taken into account.


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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 Al Wasit Grid Station in Mahadah 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.

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 2,000 Amps (i.e. 762 MVA per circuit).

In the longer term the principal technical benefits to be obtained from connecting Oman to the GCC Grid are in a reduced spinning reserve requirement, with this 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 the potential shortfall that is forecast for the last two years of the five year reporting period of this Capability Statement, i.e. 2011 and 2012. An import capacity of up to 200 MW will be available from the GCC Grid according to OPWP in its Seven-Year Statement (2007 – 2013).

The potential benefit from staggered peak demands across the grid is likely to be small, with only a one-hour time difference across the grid between Kuwait in the west and Oman in the east. Similarly with each member country reliant on the same type of generation, at least in the short to medium term, little benefits will be obtained from use of more efficient fuels.


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6.5.2. Interconnection with PDO The OETC transmission system borders with, and has a network interconnection with Petroleum Development Oman (PDO), which has its own electricity transmission system for oil exploration and development in the central region of Oman. 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 67km 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.

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 generator at Barka. However, due to technical and economic issues LDC are currently operating with a spinning reserve of less than 200 MW and relying on under-frequency load shedding and load self regulation to preserve an adequate margin.

7. Demand Forecast and Generation Availability

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 period when temperatures are at their highest. Figure 6 shows the 24-hour demand profile for the transmission system on the day of the 2007 system peak demand (i.e. 15 July 2007). The 2007 system peak demand of 2773 MW was recorded at 1500 hours by the OETC Load Dispatch Centre.


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Fig 6: OETC System Load on 2007 Peak Day (15 July 2007)

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The historic growth in system peak demand over the period (2003-2007) is shown in Table 6.

Table 6: Historic growth in peak demand and transmission losses (2003 – 2007)

2003 2004 2005 2006 2007

System Max Demand (MW) based on gross demand

2232 2371 2495 2613 2773

Annual growth rate based on gross demand (%)

--- 6.2 5.2 4.7 6.1

System Max Demand (MW) based on net demand

2139 2294 2395 2505 2662

Transmission System Losses (MW)

35 27 40 37 20

Transmission System Losses (%) 1.64 1.18 1.66 1.47 0.75


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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 2007 the system minimum demand was 489 MW and this occurred on 2 January 2007 at 0400 hours. The 2007 system minimum demand was approximately 18 percent of the 2007 system peak demand. The 24-hour profile for the day of minimum demand is shown in Figure 7.

Fig 7: OETC System load on 2007 Minimum Load Day (2 January 2007)

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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 PWP for the purposes of the statement of future capacity requirements required by Condition 5 of the PWP licence”.

The PWP demand forecast is based on data supplied 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


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220 kV or 132 kV in their respective supply areas. The distribution company forecasts are provided in terms of:

a) The growth in major industrial loads

b) The growth in major tourism loads

c) The growth in other major loads

The forecasts supplied to PWP 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 PWP does, however, include major future connections and the cumulative increase in load over the seven-year period covered by the PWP Statement. PWP 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 PWP Demand Forecast in its Seven-Year Statement.

The PWP 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 2008 to 2012, since this information is required for the power flow studies.

Analysis of the demand forecast data used by PWP in developing its Seven-Year Statement (2008 – 2014) identified basic annual percentage rates of 5, 6 and 7 percent respectively for the growth in peak demand (excluding major projects) in the Mazoon EC, Muscat EDC and Majan EC 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 2007 system peak (i.e. on 15 July, 1500hours). The demand associated with major industrial and tourism projects as assessed by PWP (with diversity8 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 demand in 2009, 2010 and 2011 and these gird stations will provide load relief to the more heavily loaded grid stations and in some cases supply new loads.

However, in the absence of any directives from the distribution companies with respect to future load transfers, OETC has assessed modest load transfer requirements between neighbouring grid stations in order to reduce future overloads and operation above firm capacity. The transfers were considered to be within the practical limits set by the connectivity of the distribution system at voltages of 33 kV and below. Table 7 summarises the load transfers that have been assumed in the studies.


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7.3. System Maximum Demand Forecast and Generation Availability Table 8 shows the grid station demand forecast for the period 2008 – 2012 with prospective load transfers taken into account and the forecast developed in accordance with the methodology described in sub-section 7.2.

Table 9 compares the total demand forecast in Table 8 with the available generating capacity in Table 5 and shows that with the planned retirements, no additional non-contracted generating capacity connected and zero power import over the cross-border interconnector with the UAE, then there will be a significant shortfall in generating capacity in Oman from 2010 onwards, reaching 525 MW by 2012.


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However, with the planned retirements postponed until sufficient new generating capacity is commissioned (i.e. after 2012) and advantage taken of the availability of non-contracted generation and imported power from the UAE, the deficit shown for 2010 to 2012 in Table 9 can be turned into a surplus as shown in Table 10.


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8. Transmission System Performance The transmission system data used in the power system studies to determine the system performance over the period 2008 to 2012 is presented in Appendix B of this Statement.

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 response of the system to 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 2008 to 2012 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 report. 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 that sufficient generation will be available from both Contracted and Non-Contracted Generating Plant to meet each annual system peak. In the studies the amount of voltage support provided by the capacitors connected to the 33 kV busbars at the grid stations was generally consistent with that identified as available by the OETC Load Dispatch Centre.

A second series of load flow studies was 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 2007 the system minimum demand was approximately one-fifth 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 11 shows the generating plant assumed to be in service at minimum load in each year of the study.

Under minimum load conditions it is assumed that all capacitive support will be switched out.


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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 2008 to 20129. These include:

percentage loading of all grid stations at system peak demand

available spare capacity at each grid station in relation to firm capacity at system peak

percentage loading of each overhead line and underground cable in the transmission system at system peak

voltage profile at each 220 kV and 132 kV busbar at maximum and minimum load

annual transmission losses at peak demand

maximum 3-phase and single-phase to earth short-circuit fault levels10

The principal findings from the power system studies are:

a) The 220/132 kV grid stations, with the exception of Al Wasit, have large amounts of spare capacity available over the period 2008 to 2012 to cope with future growth in demand.

b) The 132/33 kV grid stations, however, are more restrictive. At the summer peak in 2008, only twelve of the thirty-one 132/33 kV grid stations are expected to be operating within their firm capacity. The grid station at Nizwa was shown to be overloaded.

c) Implementation of the development projects described in Section 5 and implementation of the modest load transfer programme of Table 7 will not restore the full system to (N-1) compliance. Despite the introduction of thirteen new 132/33 kV grid stations and upgrades to another five between 2008 and 2012, there will still be fifteen grid stations operating over-firm and another grid station (i.e. Rustaq) overloaded by the 2012 peak.

d) The 220 kV circuits are all operating within firm capacity at peak demand over the five-years between 2008 and 2012, once the existing circuits between Barka Power Station and Filayj grid station are reinforced with a second double circuit line to meet peak demand in 2009.

e) The number of 132 kV circuits operating over-firm will be reduced from nine in 2008 to seven in 2012.

f) The voltage at the 220 kV and 132 kV busbars will be maintained within the +/-10 percent voltage limit at the extremes of peak and minimum demand with two exceptions. At Al Hail the voltage at peak demand will fall below 0.9 per unit in each year through to and including 2010, and at Sur where the voltage will also

9 System diagrams showing the results of the peak demand load flows have also been produced, but these are best viewed as “pdf” files because of the size of the network and the level of detail in the power system model which makes it difficult to view on A4 or A3 size paper. 10 The single-phase fault levels for the 33 kV busbars have not been presented in the report because OETC’s information on the earthing arrangement s at the 33 kV busbars of the Distribution companies is incomplete.


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fall below 0.9 per unit in 2010 before the 220 kV system is extended from Jahloot to meet the 2011 peak. The 33 kV busbar voltage at the grid stations will be maintained within +/- 3 percent of nominal voltage during these extreme load conditions.

g) The average annual power loss on the transmission system at peak demand over the period 2008 to 2012 is under 1.8 percent.

The high growth rate of the existing load coupled with major new industrial developments in Sohar and major tourism projects around the coast to the east and west of Muscat presents a major challenge to OETC in providing the capacity needed to satisfy demand over the next five years11.

The load flow studies show that whilst the planned 220 kV transmission development will add substantial new capacity to the 220 kV system and to the 220/132 kV grid stations that will enable the 220 kV transmission system to cope with new demand well beyond 2012, this is not the case with the 132 kV system and the 132/33 kV grid stations. The system developments planned for this lower voltage level will only slightly improve the situation with respect to firm capacity. Consequently the opportunities for the connection of new load will be limited to those grid stations where spare capacity exists.

The studies do show that the existing transmission system is inefficient in how it handles the flow of reactive power and will continue to be inefficient with the proposed system developments. There is an absence of reactive compensation equipment on the transmission system at 220 kV and 132 kV which would provide the necessary voltage support / voltage restraint. Consequently in many of the 220 kV and 132 kV circuits there is a substantial amount of reactive power flowing. This reduces the capacity of the circuits, increases the losses and the voltage drop. There are therefore opportunities for the provision of reactive power support under an ancillary services contract to reduce the flow of reactive power across the transmission system.

The developments proposed for Al Hail and Sur that were identified in Table 1 will provide an effective solution to the voltage problems at peak demand.

As a final cautionary note, the load flow studies of maximum demand have drawn into question the present plans to connect the 220 kV grid stations at SIS and Al Wasit in 2010 to complete the link between the 220 kV system in Oman and the UAE. The studies have shown that it will be necessary to open the 132 kV transmission system at some point between SIS and Al Wasit to prevent large power flows being sent to Al Wasit over the 220 kV system and returned over the 132 kV system. For example, in 2012 400 MW is sent to Al Wasit from SIS over the 220 kV system and 230 MW is returned to SIS over the parallel 132 kV system, effectively circulating power around a 150km loop of 220 kV and 132 kV circuits. With the 132 kV system opened then Al Wasit 220/132 kV transformers should not be overloaded in

11 The average annual growth rate between 2008 and 2012 is 9.9 percent.


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2012 as was indicated in the studies. Before the design is finalised for this scheme OETC will be re-examining the provisional rating of the 220/132 kV transformers to ensure the 220/132 kV transformers at Al Wasit will operate within firm capacity.

8.2. Fault levels The maximum 3-Phase and Single-Phase short-circuit fault levels have been determined in accordance with IEC 6090912 and as such excludes the contribution from fault level sources at lower voltages, e.g. from induction motors connected at 11 kV or below. The method is, however, valid since it is consistent with the information and data available to OETC at this time, with no information provided to OETC with regard to short-circuit backfeeds from the distribution companies at the grid station 33 kV busbars. The actual prospective busbar fault levels may therefore be 2 to 3 kA higher than those obtained in the studies presented in this Capability Statement.

The results of the fault level studies have identified a number of substations where the fault level appears in excess of the switchgear rating. However, this does not necessarily mean that the switchgear at these substations is overstressed, since none of the circuit breakers may be required to interrupt the full busbar fault current. The highest fault current that has to be interrupted will be for a fault immediately downstream of one of the outgoing feeders. OETC are concerned over this issue since it raises serious questions with respect to the safety of personnel and the switchgear equipment and as such have initiated a review of system fault levels and infeeds.

In 2008 the maximum 3-phase break duty fault levels on the 132 kV at Rusail (37.1 kA) and Ghubrah (32.2 kA) are in excess of the switchgear rating of 31.5 kA. This can be managed by imposing operational restrictions at Rusail. By 2012, however, with additional generation connected to the transmission system at Barka (Phase 2) and Ghubrah, the 132 kV fault levels at Rusail, Ghubrah, have further increased and in addition the fault levels at MS Qaboos and Boushar will also be above the switchgear rating. OETC are investigating the implications that any operating restrictions that may be needed for fault level purposes on security of supply.

The high short-circuit levels at 132/33 kV grid stations in the Muscat area are of concern and the issue is being addressed. One possible impact of this is that it could impose a limitation on the connection of new generation at Ghubrah in 2012 and lead to a reappraisal of the optimum location of new power stations in the future. It could also lead to a limitation of new connections at some grid stations in the Muscat area and signify the need to re-examine the operation of the 220 kV, 132 kV and 33 kV systems as solid busbar systems.

12 IEC 60909 defines a methodology for “The Calculation of Short-Circuit Currents in Three-Phase a.c. Systems”.


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9. Development Opportunities 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 increases the voltage drop across the transmission system. It also increases the power losses, and reduces 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 8 shows the connectivity of the OETC transmission in 2012 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, albeit that 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.

The North Coast area covers the coastal strip between Barka on the western outskirts of Muscat 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.


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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, Yankit and Seefa. However, the generation in Outer Muscat is located at Barka, around 100km 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.

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.

Table 12 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 2008 to 2012. 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. By 2010 the power balance in Central Muscat will be in deficit and this will increase in 2011 and would continue to do so if the new 400 MW plant proposed for Ghubrah was instead located outside of Muscat. However, irrespective of whether or not the new 400 MW plant is located in the Muscat area, the combination of the existing Ghubrah generation and the Barka generation will produce a surplus of generation in the Greater Muscat area. So there is no real need to locate new generation in the Muscat area unless the existing plant at Ghubrah is retired, otherwise the balance of generation and demand will be disturbed and the surplus power will then have to be exported to other areas, increasing voltage drops and system losses. The potential fault level issues at grid stations should also discourage the connection of new generating plant in Muscat.

At Nizwa, there is a modest surplus of generating capacity in each of the five-years of the Statement, so there is little need for new generation in that area.

At Sohar a generation surplus is forecast until 2012, although an accelerated growth in the port area will advance the deficit in generation and provide opportunities for the connection of new generation at the latter end of the period.

The major power deficit is in the North Coastal area where demand totalling 350 MW at summer 2008 peak increases to over 500 MW in 2012. 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 and Interior area and the Sur area will experience an increasing deficit in generating capacity over the period, so that by 2012, the deficiency in the two areas will be


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around 200 MW and 100 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, however, voltage problems in 2010 will be addressed by extending the 220 kV transmission system from Jahloot to Sur in 2011.

The main findings from the assessment of the generation ~ demand balance indicates that:

New generation should not be located in the Muscat area other than to replace the existing ageing Ghubrah power plant, although there may be a case for locating new generation closer to the resorts that are being developed just to the south of Muscat.

The forecast growth in demand in Sohar can be supplied by the existing generation, but if the growth accelerates above the present forecast then new generating plant could restore the generation ~ demand balance, but they are other private customers with generation that could help meet any emergency requirement.

The North Coastal area has a large generation shortfall over the period 2008 to 2012 and a centrally located generating plant could reduce power transfers through this area.

New generation located at Ibri or Dank in the interior could reduce power transfers over the 132 kV system and provide voltage support, although reactive compensation would be a lower cost solution to the voltage problems.

9.2. Available grid station capacity Table 13 identifies the available capacity at grid stations for the connection of new demand over the period 2008 to 2012.

The grid stations where spare grid transformer capacity of more than 10 MVA is available13 to supply new demand, are listed below on the same area basis as that presented in sub-section 9.1. The MVA figure quoted refers to the available capacity in 2012.

a) Central Muscat – Muttrah (40 MVA); Qurum (61 MVA); and Wadi Adai (11 MVA)

b) Outer Muscat – Jafnen (63 MVA); Jahloot (54 MVA); Mobella (42 MVA); Quriyat (101 MVA); Yankit (31 MVA); and Yitti (34 MVA)

c) North Coast – Muladha (34 MVA); and MIS (30 MVA)

d) Sohar – Industrial Area ‘A’ (14 MVA); and Industrial Area ‘B’ (85 MVA)

e) Border and Interior – Buraimi (23 MVA); Dank (42 MVA); Liwa (33 MVA); and Wadi Sa’a (64 MVA)

13 The available capacity was determined in relation to the firm capacity of the substation.


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f) Nizwa – Adam (14 MVA); and Bahla (38 MVA)

g) Sur – No substations have spare capacity available of 10 MVA or more.

The grid stations that provide a dedicated supply to Blue City and Azaiba Coast (Wave Project) will have 135 MVA and 46 MVA of spare transformer capacity available respectively in 2012. However, both projects will still be in the development stage at that time and much of the spare capacity will be reserved for the two projects.


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Review of Future Developments

A.1 Projects completed to meet 2008 peak demand A review of the list of major development projects that were underway on the OETC transmission system at the start of 2008 has confirmed that none of these will be available for service before the 2008 peak demand is reached in June/July 2008. Of those projects completed during 2007, the only major development that is yet to impact on the transmission system is the 220 kV cross-border interconnection between Al Wasit in north-west Oman and Al Ain in the UAE. The work on the interconnection was completed in the first quarter of 2007, but it is understood that agreement has still to be reached between the various parties with regard to the actual trading arrangements and until an agreement is reached then the interconnection will not be switched into service.

A.2 Projects expected to be completed in time to meet the 2009 peak demand

The project review, mentioned in sub-section 5.2.1, identified a number of projects that may be in service by the summer of 2009. These projects fall into two distinct categories:

c) Projects already under construction and due in service before the end of the second quarter of 2009

d) Projects that are at the tender evaluation stage prior to appointment of the preferred Contractor.

The projects that are already under construction are:

New 132/33 kV grid supply point at Adam. The new 2 x 40 MVA grid supply point (GSP) at Adam in Dakhiliya Region will be supplied directly from Manah Power Station via a 132 kV, 47km double circuit overhead line. The new GSP will provide some load relief to Nizwa 132/33 kV GSP substation and will also greatly improve the voltage for Mazoon customers in the area around Adam, that currently are fed from Nizwa, around 70km to the north of Adam. This work is scheduled to be completed in the final quarter of 2008.

New 132/33 kV grid supply point at Muladha. The new 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. The new GSP substation, which is due to come into service in the final quarter of 2008, will provide load relief to the existing Muladha (11km from MIS ) and Khabourah substations (53km from MIS).

New 132/33 kV grid supply point at Liwa. The new 2 x 125 MVA GSP at Liwa in North Batinah will provide load relief to both Shinas and Sohar Grid. The substation will be located in the first phase of the project at a point close to the existing line between Wadi Jizzi Power Station and Shinas. In the second phase the existing single circuit line between Wadi Jizzi and Shinas will be upgraded with a new double circuit line. The first phase is scheduled for


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completion in the final quarter of 2008 and the second phase is scheduled for completion in the first quarter of 2009.

New 220/132/33 kV grid supply point at Airport Heights. The new grid station at Airport Heights will be equipped with 2 x 500 MVA, 220/132 kV transformers and 2 x 125 MVA, 132/33 kV transformers. The grid station will supply new load and take load transfers from Bousher and Mawellah. The substation will be located near the 220 kV double circuit line between Al Filaij and Madinat Sultan Qaboos (MSQ) which will be looped in and out of Airport Heights. The work is scheduled for completion in the second quarter of 2009.

New 132/11 kV grid station at Azaiba Coast. The new grid station at Azaiba Coast is dedicated to supply the electricity demand from the Wave Project and will be supplied from Airport Heights via two 132 kV, 10km underground cable circuits. The work is scheduled to be completed in the second quarter of 2009.

Whilst work is proceeding on these projects a number of other projects are in the tender evaluation process prior to the appointment of a Contractor. These projects are:

Upgrade of the transformer capacity at Nizwa and Bahla grid stations. The grid stations at Nizwa (2 x 63 MVA) and Bahla (2 x 40 MVA) were both loaded above firm capacity at peak demand in 2007 and to address this situation both grid stations will have their existing transformers replaced with 2 x 125 MVA transformers. The contract for the work is expected to be placed in the first quarter of 2008 with completion thirteen months later, so that the upgrade should be completed in time to meet the 2009 peak demand.

New 132/33 kV grid station at Saham. The new grid station will be located near the existing 132 kV double circuit line between the Khabourah 132/33 kV grid station and the 220/132 kV SIS (Seh Ak Makarim) grid station and it is proposed that the double circuit line will be looped in and out Saham. The new grid station will take load transfers from Sohar grid and Khabourah.

New 220 kV double circuit line between Barka Power Station and Filaij. 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 Stage 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 in the first quarter of 2009. However, the contract award has been delayed by three months and with a fourteen-month construction period the line is not expected to be commissioned until the second quarter of 2009, but still in time for the summer 2009 peak.


Whilst the projects required to meet the 2009 peak are well advanced the projects that are in the pipeline to meet the summer peak demand in 2010 are, as may be expected, much less


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advanced, with some projects at the consultancy stage, others about to enter that stage and the rest still at an early planning stage with OETC not yet committed to the final scheme.

Those projects for which a consultant has been appointed are:

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 to the MIS 220/132 kV grid station at Musanna via a 220 kV double circuit line. The grid station is due in service during the first quarter of 2010.

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 by 2009 and a further 12 MW by 2010. To meet this requirement a new 2 x 63 MVA grid supply point is scheduled to come into service during the third quarter of 2009 at Wadi Sa’a, near Buraimi in the Dhahirah region.

132/33 kV Grid Supply Point at Yitti. The new Yitti Resort in the Muscat Governorate will be supplied from a new 2 x 125 MVA grid station at Yitti, which in turn will be fed from a new 132 kV busbar 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. The work is scheduled to be completed during the final quarter of 2009.

220 kV double circuit line between SIS (Seh Al Makarim) and Al Wasit grid stations. 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 interconnector with the UAE at 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 2009.

Second phase of development at Sohar Industrial Area 220/132/33 kV grid station. To meet the expected growth in demand in the Sohar area and ensure that the existing Sohar Industrial Area 220/132/33 kV grid substation (developed in the first phase) meets the (N-1) security requirements a second 220/132/33 kV grid substation is planned for final quarter of 2009.

The projects for which contracts are about to be awarded to a consultant are:

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 under 2007 peak load conditions, with each transformer loaded to 67 percent of rating. The proposed scheme will see the existing transformers replaced with 2 x 125 MVA transformers and the existing 132 kV double circuit line to Seeb Main from Mawellah upgraded from single 240 mm2 ACSR conductors per phase to twin “Yew” AAAC conductors per phase, more than doubling the thermal rating of the overhead line from 101 MVA to 261 MVA per circuit. A


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consultant is expected to be appointed this quarter and the work is scheduled to be completed within eighteen months of the Consultant’s contract award.

132/33 kV grid supply point at Muttrah. A new 2 x 125 MVA grid station is planned for Muttrah to take load transfers from Wadi Kabir and Falaj 132/33 kV grid stations. The new grid station will be supplied directly from MSQ 132/33 kV grid station via a new 132 kV double circuit line. The work is scheduled to be completed during the third quarter of 2009.

132/33 kV grid supply point at Qurum. The new 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 (54 percent loaded at the 2007 peak) and Wadi Adai(40 percent loaded at the 2007 peak) grid stations. The contract for the consultant is due to be awarded shortly and the work scheduled to be completed during the final quarter of 2009.

Upgrade of the 132 kV double circuit line between Al Wasit and Buraimi. The existing 132 kV double circuit line between Al Wasit and Buraimi will be rebuilt with steel lattice towers and the existing conductors replaced with those of a higher rating. The work is scheduled to be completed by the end of 2009.

The schemes that are being considered to meet the summer peak demand in 2010, but are still at an early planning stage with OETC not yet committed to the final scheme are:

220/132/33 kV grid station in the Jafnen Area. Extension of the 220 kV transmission system from Filaij to the Jafnen Area, near Rusail, is proposed. The 132/33 kV grid station is required to supply the demand (i.e. 60 MVA) at the new Oman Cement Company plant which is under construction and for which a connection application has been received. The work is due to be completed during the second quarter of 2010.

220/132 kV grid station at Jahloot. The extension of the 220 kV transmission system to Jahloot will strengthen the electricity supplies to the area along the coast to the south of Muscat where some major tourism projects are underway. The new 2 x 500 MVA grid station will be supplied via a new 220 kV double circuit line from the Jafnen Area. This project is expected to proceed with a target date for completion during the second quarter of 2010.

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 the 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. The current situation is that there are a number of options still


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being considered before OETC issue tender documents for the appointment of a consultant. Unless a consultant is appointed in the next three months then completion of the project is likely to slip into the second quarter of 2010. Any further delay could result in this project not being completed before the 2010 summer peak.

132/33 kV Grid Supply Point at Shinas Resort (Shinas 2). The electricity supply to the tourism project proposed for Shinas in North Batinah would be provided from a new 2 x 63 MVA grid station dedicated for that purpose. The new grid station would be fed from the existing 132/33 kV Shinas Grid Station via a new 132 kV double circuit line. The target date for completion of this project is the first quarter of 2010, which is still achievable, but to date no connection application has been received and the project was not included in the latest OETC budget.

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 46 percent of its rating during the 2007 summer peak and further growth is likely to see this substation operating above firm capacity by the 2008 summer peak. OETC recognise 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. Although the upgrade of Dank grid station was not included in the latest OETC budget, completion during the second quarter of 2010 is still feasible, with the award of the Consultancy Contract not scheduled until October 2008.

Upgrade of 132/33/11 kV Grid Supply Point at Ibri. The existing 2 x 63 MVA, 132/33 kV grid supply point at Ibri in the Dhahirah region was loaded to 68 percent of its rating during the 2007 summer peak and therefore well above its firm capacity. Although, the upgrade of Ibri grid station was not included in the latest OETC budget, there is a definite need to increase the transformer capacity at Ibri. The favoured options for this project is to replace the two 63 MVA transformers with 2 x 125 MVA transformers, although a cheaper solution may be to just add a third 63 MVA. With the upgrade of Ibri, the proposed construction of a new grid supply point at Dreez, some 30km from Ibri, can probably be avoided. The award of the Consultancy Contract is expected by October 2008 and the project is scheduled to be completed by the second quarter of 2010.


The projects scheduled to come on-stream in time to meet the 2011 peak demand are very few at this stage. Of those initially identified, Dreez grid station is unlikely to be required if Ibri is upgraded. Upgrading of the Al Wasit - Dank, and Ibri - Dank 132 kV double circuit lines are considered by OETC as low priority projects at this stage and have been excluded for further consideration in this Statement. This leaves the following schemes under consideration to meet the 2011 peak demand.


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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.

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 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 end of 2010.

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 and consequently the supply provided to Al Hail is not compliant with the (N-1) security requirements. Upgrading the connection with a double circuit line is considered a high priority scheme as the existing arrangement is in contravention of Licence Condition 26. Consequently the current scheduling of the scheme is undergoing a review with the Consultancy Contract not scheduled to be awarded until September 2009, the Contractor start date March 2010 and completion by February 2011. Given the potential seriousness of this issue, the timing of this project needs to be advanced so that the work can be completed as soon as possible, i.e. by summer peak 2009 if the Consultancy phase can be eliminated.


There are currently no new transmission projects scheduled to come into service between the summer peaks of 2011 and 2012.


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Appendix B Transmission System data B.1 Substations Loads and Capacitor data The grid station real and reactive power load at system peak demand for the period 2008 to 2012 and the respective reactive power support from capacitor banks connected at the grid station 33 kV busbars is shown in Table B.1.14 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 on 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 (2008) 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 2008 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.

14 The 33 kV busbars at the grid supply points and the capacitors connected to them are owned and operated by the distribution companies.


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Appendix C Power System Studies C.1 Summary of Load Flow Study results The results of the power flow studies of peak demand for each year from 2008 to 2012 are summarised in a series of tables and presented pictorially as “pdf” copies.

The study results are presented in the following tables:

Table C.1 – Grid transformer loadings at Peak Demand (2008 – 2012)

Table C.2 – Available capacity at Grid Stations (2008 – 2012) for connection of new demand

Table C.3 – Overhead line and cable circuit loadings at peak demand (2008 – 2012)

Table C.4 – Tranmission system voltage profile at peak and minimum demand (2008 – 2012)

Table C.5 – Estimation of transmission losses at peak demand (2008-2012)

C.2 Summary of Fault Level Study results The results of maximum busbar 3-phase and single phase fault levels are presented in tabular form as follows:

Table C.6 – Maximum 3-Phase Short Circuit Fault Levels

Table C.7 – Maximum Single-Phase Short Circuit Fault Levels.

C.3 Soft Copies of load flow study results The result of peak demand load flow studies for the years 2008 through to 2012 are presented as Figures C.1 to C.5 respectively. These Figures are available in soft copy “pdf” format for ease of viewing.


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OETC 2008 Approved Transmission Capability Statement[1]

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