Training R eport by Saya ntan Roy1 NTPC Limited NTPC Limited(formerly National Thermal Power Corporation) (BSE:532555,NSE:NTPC)is the largest Indian state-ownedelectric utilities company based inNew Delhi,India. It is listed inForbes Global 2000 for 2011 ranked it 348th [3] in the world. It is anIndianpublic sector company listed on theBombay Stock Exchange in which at present the Government of India holds 84.5% (after divestment the stake by Indian government on 19th October, 2009) of its equity. With a current generating capacity of 39,174 MW, NTPC has embarked on plans to become a 75,000 MW company by 2017. It was founded on November 7, 1975.NTPC's core business is engineering, construction and operation of power generating plants and providing consultancy to power utilities in India and abroad. The total installe d capacity of the company is 36,014 MW (including JVs) with 15 coal based and 7 gas based stations, located across the country. In addition under JVs, 5 stations are coal-based, and another station uses naphtha/LNG as fuel. By 2017, the power generation portfolio is expected to have a diversified fuel mix with coal based capacity of around 27,535 MW, 3,955 MW through gas, 1,328 MW through Hydro generation, about 1400 MW from nuclear sources and around 1000 MW from Renewable Energy Sources (RES). NTPC has adopted a multi-pronged growth strategy which includes capacity addition through green field projects, expansion of existing stations, joint ventures, subsidiaries and takeover of stations. NTPC has been operating its plants at high efficiency levels. Although the company has 19% of the total national capacity it contributes 29% of total power generation due to its focus on high efficiency. NTPC’s share at 31 Mar 2001 of the total installed capacity of the country was 24.51% and it generated 29.68% of the power of the country in 2008 –09. Every fourth home in India is lit by NTPC. As at 31 Mar 2011 NTPC's share of the country's total installed capacity is 17.75% and it generated 27.4% of the power generation of the country in 2010 –11. NTPC is lighting every third bulb in India. 170.88BU of electricity was produced by its stations in the financial year 2005 –2006. The Net Profit after Tax on March 31, 2006 was 58.202 billion. Net profit after tax for the quarter ended June 30, 2006 was 15.528 billion, which is 18.65% more than that for the same quarter in the previous financial year. It is listed inForbes Global 2000 for 2011 ranked it 348th [4] in the world. Pursuant to a special resolution passed by the Shareholders at the Company’s Annual General Meeting on September 23, 2005 and the approval of the Central Government under section 21 of the Companies Act, 1956, the name of the Company "National Thermal Power Corporation Limited" has been changed to "NTPC Limited" with effect from October 28, 2005. The primary reason for this is the company's foray into hydro and nuclear based power generation along with backward integration by coal mining.
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NTPC Limited (formerly National Thermal Power Corporation)
(BSE: 532555, NSE: NTPC) is the largest Indian state-owned electric utilities company based
in New Delhi, India. It is listed in Forbes Global 2000 for 2011 ranked it 348th[3] in the world.
It is an Indian public sector company listed on the Bombay Stock Exchange in which atpresent the Government of India holds 84.5% (after divestment the stake by Indian
government on 19th October, 2009) of its equity. With a current generating capacity of
39,174 MW, NTPC has embarked on plans to become a 75,000 MW company by 2017. It was
founded on November 7, 1975.
NTPC's core business is engineering, construction and
operation of power generating plants and providing consultancy to power utilities in
India and abroad.
The total installed capacity of the company is 36,014 MW
(including JVs) with 15 coal based and 7 gas based stations, located across the country.In addition under JVs, 5 stations are coal-based, and another station uses naphtha/LNG
as fuel. By 2017, the power generation portfolio is expected to have a diversified fuel mix
with coal based capacity of around 27,535 MW, 3,955 MW through gas, 1,328 MW
through Hydro generation, about 1400 MW from nuclear sources and around 1000 MW
from Renewable Energy Sources (RES). NTPC has adopted a multi-pronged growth
strategy which includes capacity addition through green field projects, expansion of
existing stations, joint ventures, subsidiaries and takeover of stations.
NTPC has been operating its plants at high efficiency levels.
Although the company has 19% of the total national capacity it contributes 29% of total
power generation due to its focus on high efficiency. NTPC’s share at 31 Mar 2001 of the
total installed capacity of the country was 24.51% and it generated 29.68% of the power
of the country in 2008 – 09. Every fourth home in India is lit by NTPC. As at 31 Mar 2011
NTPC's share of the country's total installed capacity is 17.75% and it generated 27.4%
of the power generation of the country in 2010 – 11. NTPC is lighting every third bulb in
India. 170.88BU of electricity was produced by its stations in the financial year 2005 –
2006. The Net Profit after Tax on March 31, 2006 was 58.202 billion. Net profit after tax
for the quarter ended June 30, 2006 was 15.528 billion, which is 18.65% more than
that for the same quarter in the previous financial year. It is listed in Forbes Global
2000 for 2011 ranked it 348th[4] in the world.
Pursuant to a special resolution passed by the Shareholders at
the Company’s Annual General Meeting on September 23, 2005 and the approval of the
Central Government under section 21 of the Companies Act, 1956, the name of the
Company "National Thermal Power Corporation Limited" has been changed to "NTPC
Limited" with effect from October 28, 2005. The primary reason for this is the company's
foray into hydro and nuclear based power generation along with backward integration by
Note: Though there is role of all departments only works associated with Electrical
department is highlighted compared to other departments.
General Working Procedure:
Initially NTPC starts with a Pre-Project Analysis by its specialized teams and experts.
Chalks out a plan for development of the whole setup.
An abstract containing the details of all the technical patterns that includes SLDs,
equipments specification etc.
A bill of quantity is prepared.
Tender is floated (Notice Inviting Tender).
The contractors submit their sealed tenders.
The least value of quotation is selected (L1 bidder).
Detailed study about the role of various super specialized teams:
SYSTEM GROUP
They prepare a feasibility report based on
a) Land Availability.
b) Raw material availability (water and coal).
c) Environmental Aspects.
d) Power Evacuation.
MAINPLANT GROUP
They prepare the plan and develop the main plant which consists of the whole functioning
structure that will form the basis of generation of power. This group deals with the approval
of specification of Generator, ESP and MDBFP etc.
SWITCHYARD GROUP
This group consists of mainly electrical engineers who prepare the necessary list of items and
equipments required to setup a switchyard. Initial prepare the Single Line Diagram (SLD)based on which the layout is developed the switchyard is actually laid.
They mainly take care of transformers. Various transformers (step up/step down).
PROTECTION GROUP
Set up the protective environment for all equipment related with relays which convey the
information of fault in equipment.
CABLING & LAYOUT
They prepare the cabling schedules which are best suited to feed all the drives in plant. Takescare of lighting of whole power station prepare layout of different buildings in AUTOCAD
Turbine, rotary engine that converts the energy of a moving stream of water, steam, or gasinto mechanical energy. The basic element in a turbine is a wheel or rotor with paddles,propellers, blades, or buckets arranged on its circumference in such a fashion that themoving fluid exerts a tangential force that turns the wheel and imparts energy to it. This
mechanical energy is then transferred through a drive shaft to operate a machine,compressor, electric generator, or propeller. Turbines are classified as hydraulic, orwater, turbines, steam turbines, or gas turbines. Today turbine-powered generatorsproduce most of the world's electrical energy. Windmills that generate electricity areknown as wind turbines.
Deaerator
A deaerator is a device that is widely used for the removal of air and other dissolved gases
from the feed water to steam generating boilers. In particular, dissolved oxygen in boiler
feed waters will cause serious corrosion damage in steam systems by attaching to the
walls of metal piping and other metallic equipment and forming oxides(rust). It alsocombines with any dissolved carbondioxide to form carbonicacid that causes further
corrosion. Most deaerators are designed to remove oxygen down to levels of 7 ppb by
weight (0.0005 cm³/L) or less.
Heat Exchanger
Heat exchangers are equipment that transfers heat from one medium to another. Theproper design, operation and maintenance of heat exchangers will make the processenergy efficient and minimize energy losses. Heat exchanger performance can deterioratewith time, off design operations and other interferences such as fouling, scaling etc. It isnecessary to assess periodically the heat exchanger performance in order to maintainthem at a high efficiency level. Heat exchangers may be classified according to their flowarrangement. In parallel-flow heat exchangers, the two fluids enter the exchanger at thesame end, and travel in parallel to one another to the other side. In Counter- flow heatexchangers the fluids enter the exchanger from opposite ends. The counter currentdesign is most efficient, in that it can transfer the most heat. See countercurrentexchange. In across-flow heat exchanger, the fluids travel roughly perpendicular to oneanother through the exchanger.
Super HeaterA super heater is a device in a steam engine that heats the steam generated
bytheboileragain, increasing itsthermal energy and decreasing the likelihood that it will
Economizers, or in British English economisers, are mechanical devices intended to
reduce energy consumption, or to perform another useful function like preheating a fluid. The term economizer is used for other purposes as well. In simple terms, an economizer
is a heat exchanger.
Condenser
The surface condenser is a shell and tube heat exchanger in which cooling water is
circulated through the tubes. The exhaust steam from the low pressure turbine enters
the shell where it is cooled and converted to condensate (water) by flowing over the tubes
as shown in the adjacent diagram.
Feed water heater
In the case of a conventional steam-electric power plant utilizing a drum boiler, the
surface condenser removes the latent heat of vaporization from the steam as it changes
states from vapour to liquid. The heat content (btu) in the steam is referred to as
Enthalpy. The condensate pump then pumps the condensate water through a feed water
heater. The feed water heating equipment then raises the temperature of the water by
utilizing extraction steam from various stages of the turbine. Pre-heating the feed water
reduces the irreversibilities involved in steam generation and therefore improves the
thermodynamic efficiency of the system. This reduces plant operating costs and also
helps to avoid thermalshock to the boiler metal when the feed water is introduced backinto the steam cycle.
Electrical Generator
In electricity generation, an electrical generator is a device that converts mechanicalenergy to electrical energy, generally using electromagnetic induction. The reverseconversion of electrical energy into mechanical energy is done by a motor, and motorsand generators have many similarities.A generator forces electric charges to move through an external electrical circuit,but it does not create electricity or charge, which is already present in the wire of its
windings. It is somewhat analogous to a water pump, which creates a flow of water butdoes not create the water inside. The source of mechanical energy may be a reciprocatingor turbine steam engine, water falling through a turbine or waterwheel, an internalcombustion engine, a wind turbine, a hand crank, the sun or solar energy, compressedair or any other source of mechanical energy.
The objective of this chapter is to describe the various technical alternatives and
considerations while designing switchyard layout.
Substation layout consists essentially in arranging a number of switchgear components inan orderly pattern governed by their function and rules of spatial separation as described in
electrical single line diagram.
Pre requisites
i) Single line diagram must be finalized before designing the layout.
ii) General Layout Plan of the Power project
iii) Orientation of Line evacuation corridor.
Options / Alternatives
The layout will vary for the following:• Switching schemes
• Type of insulation - Air Insulated/Gas Insulated.
Design Philosophy / Practice
For designing a switchyard layout, various aspects are considered which are described
here under1. Space around the switchyard . Adequate space should be allowed to provide for
extension of the switchyard facilities when generating units or transmission lines
are added in the future. The immediate surroundings should permit the routing oflines to the switchyard area from at least one direction without the need for heavy
dead-end structures in the yard.2. Switchyard location . The switchyard should be sited as near to the main plant as
space permits, in order to minimize the length of control circuits and power feedersand also to enable use of service facilities located in the main plant.
3. Switchyard fencing . A chain link woven wire fence not less than 3.0 m height
above toe wall, with lockable gates, should be provided to enclose the entire yard
from safety point of view.
4. Clearance. The placement of equipment in EHV switchyard is greatly affected by
the air clearances to be adopted. They are as follows:• Earth Clearance: this is the clearance between live parts and earthed structures,
walls, screens and ground. A minimum height of live conductors above groundmust be maintained. Also there should be a certain minimum height of supportsof various equipment (depending upon the fact that the bottom of any insulator
has to be 2.5 meters above the ground level as statutory clearance).• Phase Clearance: this is the clearance between live parts of different phases.• Isolating Distance: this is the clearance between the terminals of an isolator and
the connections thereto.• Section Clearance: this is the clearance between live parts and the terminals of a
work section. The limits of this work section, or maintenance zone, may be the
ground or a platform from which the man works.The clearances to be selected are based on the insulation level. Insulation level is
the test voltage value (both power frequency and impulse) which characterizes the
insulation of the equipment with regards to its capability of withstanding thedielectric stresses. The insulation level is generally expressed by the value of the
power frequency test voltage and the full wave impulse test voltage.
The value of the minimum clearance required is a function of powerfrequency over-voltage and/or transient over voltage caused by switching or lightning.
Lightning over voltages are critical for substation upto 220 kV and over voltages due to
switching operations are important for 400 kV substations. In line with therecommendation of IE Rules/Indian Standard/ standardization committee
recommendations.
Considering conductor swing, attraction due to short circuit, maintenance requirement,
dimensions of equipment available etc., the phase to phase spacing, sectional clearanceand phase to earth clearances has been selected and as such the width of one bay as
54/27.0 m for 765/400kV respectively. Bay width for 132kV system is 12.0 m.
Sectional clearance is achieved as phase to earth clearance + clearance to the ground
from the lowest part of insulator. Deviation angle for terminal/take off gantry is kept as± 30o in horizontal plane and ±20o in vertical plane.
5. Equipment spacing. The spacing for the placement of equipment, between them isdecided by considering
1) Ease of maintenance/removal of equipment
2) Equipment foundation & their cable trenches.
3) Distance between LA and equipment based on the protection reach of LA.The spacings are generally kept in order to achieve various clearances specified at
Table-I.
6. Bus bars
The bus bars of 765 kV switchyard can be made up of Quad AAC “Bull” conductor
or equivalent Moose / 6” IPS (EH type). The bus bars of 400 kV switchyard are made
up 4 “IPS aluminium tube/ Quad Moose rated for 3000 A. The busbars of 220/132kV
switchyard are made up of 3 “IPS aluminium tube/ twin moose conductor. Busbars are placed at right angles to feeders.
7. Equipment I nterconnection
Equipment interconnection will be carried out with Quad AAC “Bull” conductor or 6” IPS (EH type) for 765kV and 4" IPS aluminium tube or twin ACSR Moose for 400kV. For
132kV system equipment interconnection will be carried out with 3 “ IPS
aluminium tube/ Moose conductor. The bus post insulators shall be of solid core typewith cantilever strength of 800 kg for 765/400kV system, 600kg for 220kV system and
500kg for 132kV system.
8. Spacer spans and locations
The spacers will be located as away from the critical span as possible. The spacerlocation are based on the calculations of short circuit forces on strung bus and critical
span (refer separate guide line).
9. Connection Level
Place all equipment at ground level for ease of maintenance. Lower level connectionscan be of Rigid pipe or flexible conductor but upper level connections can be of strungtype only. For aesthetic looks and similarity all same equipments be in one line as far as
possible. For 765kV system, „I-type‟ design, there would be 3 levels viz first level or equipment. Level - 14m, second level or bus level - 26m and third level or jack bus
level - 38m. For 400kV,‟D-type‟ system there would be 2 levels viz first level or equipment level - 8 m, and jack bus level - 15 m. For 220kV system, there would be3
levels viz first level or equipment. Level – 5.9m, second level or bus level – 11.7 m and
third level or jack bus level – 16.2m. For 132kV system there would be 3 levels viz firstlevel or equipment. Level – 4.6m, second level or bus level – 8.5 m and third level or
jack bus level – 12.2 m. Double insulator strings should be provided for upper level for
safety reasons and to avoid busfaults due to conductor snapping.Connection to SwYard to the Generator Transformers & Station Transformers shall be
generally through overhead conductors.If the distance between the swyard and the
power Plant is more then intermediate Gantries are provided and strung upto PowerPlant building to take the dropper to the Generator & Station Transformers.sometimes
if stringing is not possible than Station Transformers are connested through EHV
Cable.
suspended on gantries or any live structure of the switchyard as per IE rules. Thelighting along the road shall be achieved by providing suitable fixtures on lighting
poles. Different illumination levels and type of lighting fixures and lighting design in
Switchyard shall be as specified. Refer guideline on Lighting for more details.
14. Cabling Phi losophyWhile preparing the cable layouts, consideration shall be given to the
requirements of segregation, separation, operation, maintenance, safety, reliability,
environment, erection, programme, convenience of cable laying and termination. Thesubstation area should be properly graded so that rain water is drained away from the
cable trenches. All cables used in switchyard are armoured type due to induced
voltages. There are two types of cables used in a Switchyard viz. Power cables andcontrol cables. The sizes for power cables vary from 31/2 X 35mm2 to 2cX 6 mm2 and
for control cables it varies from 5c X2.5 mm2 to 27cX2.5 mm2. Refer guideline on
cable routing in switchyard for more details.
15. Gravel F il li ng
Gravel or surface material coverings, usually upto 150mm in depth, are useful
in retarding the evaporation of moisture and thus in limiting the drying of topsoil
layers during prolonged dry weather periods. Also covering the surface with gravelincrease the surface resistance and thus reduces shock currents.
16. Earthing System
Earthing system for the entire power plant switchyard and other areas shall be provided in accordance with IEEE-80 and IS 3043. The soil quality and other site
conditions shall be assessed, and the grounding system will be designed for a life
expectancy of at least forty (40) years. The sizing of earthing conductor would be
based on the maximum ground fault current that is expected to occur during thedesign life of the station. Criterion in deciding spacing between buried earthmat
conductors is to limit touch voltage and step voltages within permissible values. Refer
guideline on earthing for more details.
17. Li ghtni ng Protection System
Lightning protection system shall be designed in line with “Razevig method for
DSLP” and other IE regulations. The system would comprise air terminations, down
conductors, test links and earth connections. Lightning conductor shall be ofgalvanised steel (75X12 flat) when used above ground level & mild steel (40mm
dia.)when used below ground level. Refer guideline on lightning protection for more
Laying out a substation involves a step by step procedure. Most important points to be considered are briefly described below:
• The important electrical parameters are established by the system design. Themain parameters are:
Voltage class and basic insulation level or switching surge level, site andclimatic conditions, method of circuit connection and switching overvoltage
conditions. The bus bar system diagram, the number of circuits and their purpose. i.e
control of generators, transformers, feeders etc. the diagram should includedetails of extensions and future conversion to a different busbar system, if
intended.
The continuous current rating of the busbars and circuits.
The short circuit rating of busbars and equipments.
Particulars of reactors, neutral earthing equipment and reacting,interconnecting transformers required.
Method of connection of circuits, whether by overhead lines or cables.
Details of lightning protection equipment.
Details of protective equipment, determining the instrument transformersrequirements, carrier current equipment etc.
The extent to which circuit and busbar outages for maintenance will be
possible.
17. Li ghtni ng Protection System
Lightning protection system shall be designed in line with “Razevig method for
DSLP” and other IE regulations. The system would comprise air terminations, down conductors, test links and earth connections. Lightning conductor shall be of
galvanised steel (75X12 flat) when used above ground level & mild steel (40mm
dia.)when used below ground level. Refer guideline on lightning protection for more
details.18. Steps in evolving a substation layout
Laying out a substation involves a step by step procedure. Most important points to
be considered are briefly described below:
• The important electrical parameters are established by the system design. Themain parameters are:
Voltage class and basic insulation level or switching surge level, site andclimatic conditions, method of circuit connection and switching overvoltageconditions.
The bus bar system diagram, the number of circuits and their purpose. i.e
control of generators, transformers, feeders etc. the diagram should includedetails of extensions and future conversion to a different busbar system, if
intended.
The continuous current rating of the busbars and circuits.
The short circuit rating of busbars and equipments.
Particulars of reactors, neutral earthing equipment and reacting,interconnecting transformers required.
Method of connection of circuits, whether by overhead lines or cables.
Details of lightning protection equipment.
Details of protective equipment, determining the instrument transformersrequirements, carrier current equipment etc.
The extent to which circuit and busbar outages for maintenance will be possible.
• Some parameters which influence the form of the layout are determined by thelocal conditions. These are:
The available land area, site and climate conditions, planning authority
requirements and aesthetic considerations determine the type of substation.
The direction of overhead line entry position available for terminal towers,location of transformers and reactors, etc.
The availability of materials and the transport and access facilities.
The capability and skill of the maintenance staff determines the importance ofclarity of layout and simplicity of maintenance zoning.
• The first step in layout preparation is to make a fully detailed single line diagram.this should show the position of instrument transformers, surge diverters etc. and
should include all future equipment also. the current rating of busbars and
circuits and the short circuit rating of the equipment should be added to the
diagram.
• Selecting components: Various equipment such as circuit breakers, isolators, etc.
are selected to suit the ratings required and the preference of type and their overalldimensions are established. if it is intended at a later date to operate theequipment in terms of current or short circuit level, provisions should be made for
this in determining the dimensions.
• While meeting all the needs established the following ideals should be aimed at inmaking the basic circuit layout.
Minimum ground area
Minimum quantities of conductor, joints and structure
Minimum number of independent insulators, especially in the bus bar zone.
• After having determined the electrical clearance be used a rough circuit layout ismade. Several possible alternatives are prepared from which the most suitable
one will be selected. Some variation is needed, to meet the requirements ofdifferent types of circuit.
• It is also necessary to calculate short circuit and atmospheric forces to determinethe stresses in conductors, insulators and structures. these held in deciding themost optimum dimensions.
19. Execution sequence for a substation
a. Tower foundation b. Equipment foundation
c. Laying of Cable trench
d. Laying of Earthmat
e. Support structure installationf. High level stringing
g. Equipment installation
h. Equipment interconnection
i. Cabling layout j. Commissioning
References 1. Manual on substations-Equipment, Illumination and Layouts, CBIP2. IEEE 80