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CONTENTS:-
Title Page no.
Abstract
Chapter 1
1)Introduction of NTPC 3
1.1)Overview 3
1.2)Company profile 3-6
1.3)organization and hierarchy 6-7
1.4)Mission and vision 7
1.5)Core value of NTPC 10
1.6)Power scenario in India 10-11
1.7)Aims and objective 12
Chapter 2
2)Economy of power generation
2.1)Introduction 13-17
2.2)Selection of type of generation 17
2.3)Cost of generation 18-19
3)Power generation process
3.1)Principle operation process 20
3.2)Silent feature of gas and steam turbine 21
3.3)Equipment of power plant 22-29
Chapter 3
4)Introduction of 220kv switchyard 29-33
5)Equipment in switchyard 33-51
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Appendix A
Conclusion 50
References 51
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INTRODUCTION
Nranking of the World’ s biggest companies. NTPC became a Maharatna company in
May, 2010, one of the only four companies to be awarded this status. It received
International Project Management Association (IPMA) award in 2005 for excellence
in project management for its Simahadri Project and in 2008 its Vindhyachal Project
received Silver medal from IPMA. NTPC is the largest power generation in the
country with an installed capacity of 34,854 MW (including Joint Ventures). Today,
NTPC with an installed c apacity of about 18% of country’ s total capacity is
contributing about 28% of the electricity generated, which depicts the high level of
operational performance, that are comparable with any of the global power utilities.NTPC has adopted a vision - “To be the world’ s largest and best power producer,
powering India’s growth”. NTPC has plans to have an installed capacity of 75 GW by
2017 reaching to 128GW by 2032. Capacity of over 7000 MW unit is already under
construction and another over 7000 MW under request by NTPC under its portfolio.
1.1.2. NTPC Installed Capacity
NTPC installed capacity region wise is mentioned below in the table:
REGI ON COAL GAS TOTAL
Northern 8,015 2,312 10,327
Western 6,860 1,293 8,153
Southern 4,100 350 4,450
Eastern 7,900 - 7,900
JVs 1,424 1,940 3,364
TOTAL 28,299 5,895 34,194
Table 1.1 Total i nstalled capacity of NTPC
1.2. Company Profile
Organizational Environment : -
National Thermal Power Corporation Ltd. (NTPC) was incorporated in 1975 by an
Act of parliament, to supplement the efforts of the states for quicker and greater
capacity addition in
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Thermal power generation. In 1997, the Department of Public Enterprises,
Government of India granted, Navratna (Nine Jewels) status with powers of
operational autonomy to the board of NTPC with an objective to turn the public sector
enterprise into a global giant. This has helped NTPC in speedy implementation of
power projects, adoption of new technologies and formation of Joint Ventures in the
core generation as well as service businesses.
Recently NTPC has bee n awarded the “MAHARATNA” status which has given it
greater autonomy. In line with its vision and mission statement over the last thirty five
years NTPC has grown to become the largest power utility in India with a
commissioned generation capacity of 31,704 MW (as on 31.03.2010) with power
stations spread over the length and breadth of the country, covering portfolios in coal
based and combined cycle power plants Besides, being India’s largest power
generation utility, NTPC has also grown to become the number one independent
power producer in Asia and second globally in 2009 (by Platts, a division of
McGraw-Hill companies), 5th largest company in Asia and 317th Largest company in
the world (FORBES ranking – 2009) with Net Sales of Rs. 46,504.47 crore during
2009-10.
NTPC has also the honor of becoming the 6th largest thermal power generator in the
world and second most efficient in terms of capacity utilization amongst top 10
utilities in the world. NTPC has been re- christened as “NTPC Limited” since 7th
Nov. 05.
Today NTPC is more than a company. It is an institution, which has moulded the
economy of India setting many landmarks particularly in power plant engineering,
operation and maintenance, contract management that other power organisations
would strive to emulate.
Investor’s ProfileTo augment capital outlay, NTPC made an Initial Public Offer (IPO) in Oct. 2004
and subsequent Further Public Offer (FPO) in Feb 2010. With this disinvestment, the
ownership of GOI has reduced to 84.5%.Presently NTPC is one of the three largest
Indian companies in terms of market cap.
1.2.1. NTPC Anta
1 Approved capacity 413 MW
2 Location Baran, Rajasthan3 Gas Source HBJ Pipeline- South Basin
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Gas Field
4 Beneficiary States
Uttar Pradesh,Jammu &
Kashmir,
Chandigarh, Rajasthan,
Haryana, Punjab,
Himachal Pradesh, Delhi
& Uttaranchal
5 Approved Investment Rs. 418.97 Crore
6 Unit Sizes 3X88.71 GT + 1X153.2 ST
7 Unit Commissioned
Unit - I 88 MW GT January
1989
Unit - II 88 MW GT March
1989
Unit - III 88 MW GT May
1989
Unit - IV 149 MW ST March
1990
8 International Assistance IBJ and World Bank
9 Water Source Anta Kota Right Main Canal
Table 1.2 Detail s of NTPC Power Pl ant at Anta
1.2.2. Site Approach
The plant site is 2 KM form Anta Railway Station which is about 50 KMs from Kota.
The installed capacity of the plant is 419.33 MW. It consists of three gas turbines of
ABB make type 13D-2 of 88.71 MW capacity and one steam turbine of 153.2 MW
capacity. The three numbers of WHRBs are unfired boilers supplied by WAAGNER-
BIRO. The WHRB (Waste Heat Recovery Boiler) have horizontally arranged finned
tubes with separate high and low pressure systems and condensate preheating, forced
circulation.
The main fuel for the plant is Lean Natural Gas and alternative fuel is Naphtha. GAIL
supplies the Natural gas for the plant from HBJ pipeline through a branch line and
GAIL and oil majors IOCL, BPCL& HPCL as per requirement, supply naphtha. The
circulating water requirement for condenser cooling is met by taking water from the
Kota Right Main Canal (RMC), through CW intake channel. Kota RMC is an
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irrigation canal and its opening depends upon irrigation requirements. During open
cycle operation of CW system, the water is passed through condenser and flows back
to RMC. During the closed cycle operation the water is drawn from Raw Water
Reservoir for make up by two numbers of CW system is supplied from the same.
F igur e 1.1: View of M ain Plant
Employee Profile:
The employee strength of ANTA is 221 as on May 2010. Power generation being
highly technology intensive, most of the employees are Engineers and technicians.
Executives are from professional background, supervisors and workmen are from
technical / graduate background. Contract workforce (average150 nos.) is also
engaged for Skilled/ semi – skilled/un-skilled jobs. The employee is organized into
Executive Association, Supervisors Association and Workers Union.
Democratically elected representatives manage association and unions.
1.3. Organization and Hierarchy
1.3.1. Organization Chart – NTPC Anta
NTPC s current 3 -tier structure comprises Corporate Centre (CMD, Board ofdirectors & corporate functions), Regional Headquarters (five in numbers – NCR, NR,
SR, ER and WR) and stations/Projects, ANTA being one of the stations. Anta falls
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under NCRHQ. The business unit head of ANTA is the General Manager (GM). The
power generation is handled by Operations and Maintenance department headed by
AGM (O&M), reporting to GM. O&M consists of different sections viz. Operations,
Mechanical Maintenance, Electrical Maintenance, C&I maintenance, Chemistry,
EEMG, MTP , each subsection is headed by a DGM/ Senior Manager. The support
function Departments are F&A, HR, Contracts.
1.4. Mission and Vision of NTPC
NTPC s vision and mission are driving force in all our endeavors to ultimately
produce and deliver quality power in optimum cost and eco-friendly manner through
concerted team efforts and effective systems. Being a PSU, Anta has derived its
mission and vision aligning with that of the Corporate Mission and Vision.
VISION: “A world class integrated power major, powering India’ s growth, with
increasin g global presence.”
MISSION : “Develop and provide reliable power, related products and services at
competitive prices, integrating multiple energy sources with innovative and eco-
friendly technologies and contribute to society.”
1.5. Core Values of NTPC
The Core Values (BCOMIT), as of NTPC epitomizes the organizational culture and is
central to every activity of the company. The values create involvement of all sections
of the employees. The core values are widely communicated for the actualization
among the employees.
Business Ethics
Customer Focus
Organizational and Professional Pride
Mutual Respect and Trust
Innovation and Speed
Total Quality for Excellence
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1.6. Power Scenario in India
1.6.1. India’s Installed Capacity
In India Electricity are generated state level, central level and private. Overallinstalled capacity in these sectors is as on 30.04.2011.
SECTOR MW %
States 82452.58 47.29
Central 54412.63 31.21
Private 37496.19 21.5
Total 174361.4 100
Table 1.3 I nstalled Capacit ies by Di ff er ent Sectors
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The total installed capacity by fuel is mentioned in the table :
FUEL M W %
Coal 94,653.38 54.29
Gas 17,706.35 10.15
Oil 1,199.75 0.69
Total Thermal 1,13,559.48 65.13
Hydro 37,567.40 21.25
Nuclear 4,780 2.74
Renewable 18,454.52 10.58
Total 1,74,361.40 100
Table 1.4 Total I nstalled Capacity by F uel
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F igur e 1.2: India’ s I nstalled Capacity F uel Wi se
1.6.2. Consumption of Electricity in India
Day by day the consumption of electricity is increasing and it assumed that on 2012
consumption will be 1000 KWh per annum.
YEAR PER CAPIT A CONSUM PTI ON
1950 15 KWh/per year
2007 672 KWh/per year
2012- Target 1000 KWh/per year
Table 1.5: Per Capita Consumption
0
20000
40000
60000
80000
100000
120000
140000
160000
180000
THERMAL NUCLEAR HYDRO RES TOTAL CAPTIVE
112824
4780
37567
18455
174361
19509
INDIA'S INSTALLED CAPACITY FUEL WISE
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1.7. Aims & Objectives
The National Electricity Policy aims at achieving the following objectives:
Access to Electricity - Available for all households in next five years
Availability of Power - Demand to be fully met by 2012. Energy and peakingshortages to be overcome and adequate spinning reserve to be available.
Supply of Reliable and Quality Power of specified standards in an efficient
manner and at reasonable rates.
Per capita availability of electricity to be increased to over 1000 units by 2012.
Minimum lifeline consumption of 1 unit/household/day as a merit good by year
2012.
Financial Turnaround and Commercial Viability of Electricity Sector.
Protection of con sumer’s interests.
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CHAPTER 2
2. ECONOMICS OF POWER GENERATION
2.1. Introduction
The function of a power station is to deliver power at the lowest possible cost per kilo
watt hour. This total cost is made up of fixed charges consisting of interest on the
capital, taxes, insurance, depreciation and salary of managerial staff, the operating
expenses such as cost of fuels, water, oil, labor, repairs and maintenance etc.
The cost of power generation can be minimized by:
1. Choosing equipment that is available for operation during the largest possible % of
time in a year.
2. Reducing the amount of investment in the plant.3. Operation through fewer men.
4. Having uniform design
5. Selecting the station as to reduce cost of fuel, labor etc.
All the electrical energy generated in a power station must be consumed immediately
as it cannot be stored. So the electrical energy generated in a power station must be
regulated according to the demand. The demand of electrical energy or load will also
vary with the time and a power station must be capable of meeting the maximum loadat any time. Certain definitions related to power station practice are given below:
Load Curve:
Load curve is plot of load in kilowatts versus time usually for a day or a year.
Load Duration Curve:
Load duration curve is the plot of load in kilowatts versus time duration for which it
occurs.
Maximum Demand:
Maximum demand is the greatest of all demands which have occurred during a given
period of time.
Average Load:
Average load is the average load on the power station in a given period (day/month or
year)
Base Load:
Base load is the minimum load over a given period of time.
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Connected Load:
Connected load of a system is the sum of the continuous ratings of the load
consuming apparatus connected to the system.
Peak load:
Peak load is the maximum load consumed or produced by a unit or group of units in a
stated period of time. It may be the maximum instantaneous load or the maximum
average load over a designated interval of time.
Demand Factor:
Demand factor is the ratio of maximum demand to the connected load of a consumer.
Diversity Factor:
Diversity factor is the ratio of sum of individual maximum demands to the combined
maximum demand on power stations.
Load Factor:
Load factor is the ratio of average load during a specified period to the maximum load
occurring during the period.
Load factor = Average Load / Maximum demand
Station Load Factor:
Station load factor is the ratio of net power generated to the net maximum demand on
a power station.
Plant Factor:
Plant factor is the ratio of the average load on the plant for the period of time
considered, to the aggregate rating of the generating equipment installed in the plant.
Capacity Factor:
Capacity factor is the ratio of the average load on the machine for a period of time
considered, to the rating of the machine.
Demand Factor:Demand factor is the ratio of maximum demand of system or part of system, to the
total connected load of the system, or part of system, under consideration.
Utilization Factor:
Utilization factor is the ratio of maximum demand of a system or part of the system,
to the rated capacity of the system, or part of the system, under consideration.
Firm Power:
Firm power is the power intended always to be available even under emergencyconditions.
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Prime Power:
Prime power is the maximum potential power constantly available for transformation
into electrical power.
Cold Reserve :
Cold reserve is the reserve generating capacity that is available for service but not in
operation.
Hot Reserve:
Hot reverse is the reserve generating capacity that is in operation but not in service.
F igur e 2.1 Monopoly M odel
Spinning Reserve:
Spinning reserve is the reserve generating capacity that is connected to the bus and
ready to take load.
Run of River Station:Run of river station is a hydro-electric station that utilizes the stream flow without
water storage.
Base Load Supply:
In inter connected systems with many generating stations of various types; the choice
of station to supply the varying load is of considerable economic significance. Entire
load of the system may be divided into two parts e.g., base load and peak load. Base
load is the load which is supplied for most of the time which remains more or lessconstant. Peak load is the intermittent requirement at particular hours of the day and
so on.
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The main considerations for base load provision are:
(i) High efficiency
(ii) High availability of the system.
Even a higher capital cost is sometime favoured if it can ensure resultant gain in
efficiency, as the cost is spread over a large total energy value.
Nuclear power plants are invariably used as base load plants. Thermal power plants
and hydroelectric power plants can also be used as base load plants.
As far as peak load plants are concerned, these plants should have:
(i) Ability to start and take full load with a short time
(ii) Low capacity cost in view of the small annual output with the efficiency only a
secondary condition.
Obsolete steam plant, through less efficient can't be used to met with peak load
demand. Gas turbines, diesel engine plant and pumped storage stations are also
suitable for peak load operation.
Peak Load:
Load on a power plant seldom remain constant. The load varies from season to season
and also in a day from hour to hour. In summer, due to fans and air conditioners the
plants have generally high load as compared to winter months. During day time also
lights are switched on in the evening, the load on the plant will increase. During the
days of festivals like national festivals, national days etc., there is excessive demand
of electrical power. A power generating plant has to meet with all such variable
demand sand at the same time maintain overall economy of operation. The period
during which the demand on a power station is highest is known as peak load. Peak
load on a plant may exist for small duration but still the plant has to devise ways and
means for meeting with such demands.
Some of the methods are given below to meet with peak load demand:1. Peak Load Plants:
Such plants arc operated only during peak load periods. These plants must be capable
of quickly starting from cold conditions. Diesel engine plants, gas turbine plants,
pumped storage plant and sometimes steam power plants and hydroelectric plants are
used as peak load plants. Efficiency of such plants is of secondary importance as these
operate for limited period only.
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2. Use of Accumulators:
Although electrical energy cannot be stored, however steam can be stored in steam
accumulators, which can be used to generate additional power during peak load
period.
3. Purchasing Power:
When a power plant cannot generate sufficient power to meet with the demand, it may
purchase power from neighboring plants if facilities exist.
4. Load Shedding:
When there is no alternative available the supply to some consumers is cut off
temporarily, which is known as load shedding. Sometimes load shedding is done by
switching off feeders by rotation or by reducing system voltage or by reducing
frequency.
2.2. Selection Of Type Of Generation
2.2.1. Cost of Electrical Energy
Capital cost of a power plant is due to
1. Cost of land and buildings
2. Cost of generating equipment and accessories
3. Cost of transmission and distribution network
4. Cost of designing and planning the power station
In general following plants are preferred for base load operations:
1. Nuclear power plant
2. Hydro electric plant
3. Steam power plant
Following points are preferred for peak load operations:
1. Diesel engine power plant.
2. Gas turbine power plant
3. Pumped storage plant.
2.3. Cost of Generation
The cost of generating electricity in a power plant can be conveniently split into two
parts: fixed costs and variable costs.
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(A) Fixed Cost:
Fixed costs are to be borne by the plants irrespective of the load. These costs consists
of following:
(i) Interest on Capital:
Capital cost of a plant includes the cost of land, buildings, of equipment including
installation, designing, engineering etc. Since the capital cost of a plant is fixed
therefore interest on the amount is considered as fixed cost.
(ii) Taxes:
A power generating and distributing company has to pay taxes to the Government;
this amount is more or less fixed.
(iii) Cost of Transmission and Distribution:
Power transmission and. distribution network involves huge capital expenditure. This
involves cost of transmission lines, transformers, substations and associated
equipment. Interest on the capital involved is considered as a fixed cost.
(iv) Depreciation:
It is decrease in value caused by the wear due to constant use of equipment under the
Income tax laws there is provision for setting aside a fixed proportion of the capital
employed, towards the depreciation fund.
(v) Insurance:
The plant and also life of some of workers working in dangerous areas, has to be
insured against various risks involved. For this purpose a fixed sum is payable as
premium for the insurance cover.
(vi) Salary for Managerial Staff:
Irrespective of whether the plant works or not certain managerial staffs has to be
retained by the organization. The salary liability of such staff is a part of the fixed
cost.(B) Variable Cost:
These costs vary in some proportion of the power generated in a plant. These costs
consist of-
(i) Cost of Fuel:
Cost of fuel is directly related with the amount of power generated. For generating
more power, more fuel is required. Cost of fuel may be 10% to 25% of the total cost
of production. In case of hydroelectric plants the cost of fuel is zero.
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(ii) Maintenance and Repair Charges:
In order to keep the plant in running condition, certain repairs are always needed.
Stock of some consumable and non- consumable items has got to be maintained. All
chargers for such staff are considered as operating costs.
(iii) Wages:
Salaries including allowances bonus, benefits etc. for the workers are considered as
operating costs. Total cost of production is thus sum of the fixed charges and the
operating charges. As the plant load factor improves, the cost per kWh decreases. The
sum of the charges for various factors will give an optimum load factor where such
charges will be least.
2.4. Tariff
A tariff is the rate of charge per kilowatt hour of energy supplied to a consumer. The
cost of generation of electrical energy may be conveniently split into two parts e.g.
fixed charges plus the operating charges. So a tariff should be adjusted in such a way
that the total receipts balance the total expenditure involved in generating the energy.
There are several solutions to this problem, some of which are given below:
1. Uniform Rate Tariff:
In this case there is a fixed rate per unit amount of energy consumed. The
consumption of energy is measured by the energy meter installed at the premises of
the consumer. This type of tariff accounts for all the costs involved in the generation
of power. This is the simplest tariff easily understood by consumers. However, this
type of tariff does not distinguish between small power domestic consumer and bulk
power industrial consumers.
2. Two Part Tariff:
In this the total charges are split into two parts - fixed charges based on maximum
demand (in kW) plus the charges based on energy consumption (in kWh). Thismethod suffers from the drawback that an additional provision is to be incorporated
for the measurement of maximum demand. Under such tariff, the consumers having
'peaked' demand for short duration are discouraged.
3. Block Rate Tariff:
In this the fixed charges are merged into the unit charges for one or two blocks of
consumption, all units in excess being charged at low or high unit rate. Lower rates
for higher blocks are fixed in order to encourage the consumers for more and moreconsumptions. This is done in case the plant has got larger spare capacity. Wherever
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the plant capacity is inadequate, higher blocks are charged at higher rate in order to
discourage the consumers for higher than minimum consumption.
4. Three Part Tariff:
It is an extension of the two part tariff in that it adds to the consumer some fixed
charges irrespective of the energy consumption or maximum demand. In this ever if
the consumer has got zero power consumption, he has to pay some charges merely
because a connection has been provided to him.
5. Power Factor Tariff:
In ac power supply size of the plant is determined by the kVA rating. In case the
power factor of a consumer installation is low, the energy consumption in terms of
kW will be low. In order to discharge such consumers, power factor tariff is
introduced, which may be of the following types.
(a) Maximum kVA demand Tariff: In this instead of kW the kVA consumption is
measured and the charge are Based partly or fully on this demand.
(b) Sliding Scale: In this case the average power is fixed say at 0.8 lagging. Now if
the power factor of a consumer falls below by 0.01 or multiples thereof, some
additional charges are imposed. A discount may be allowed in case the power factor is
above 0.8. The depreciation on the plant is charged by any of the following methods:
1. Straight Line method
2. Sinking fund method
3. Diminishing value method.
.
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CHAPTER3
3. POWER GENERATION PROCESS
3.1. Principle of Operation of Combined Gas and Steam Plant
The process of generation of power at ANTA is briefed. The Gas/Naphtha from
pipeline is taken and supplied to GT Combustion Chamber where it is burnt as fuel
along with air drawn from atmosphere. This heat is then converted into mechanical
energy in the Gas Turbine. Gas turbine through a common shaft rotates a Generator,
which produces electric power.
Flue gas from the turbine exhaust is used to convert water into steam in the Waste
Heat Recovery Boiler or HRSG. Water required for steam generation is circulated
through the tubes in the boiler, where heat exchange takes place and water gets
converted into
steam. The steam generated from WHRBs is used to run a steam turbo generator &
produce electric power. This power is supplied to customer through 220 KV lines.
3.2. Salient Features
Gas Tur bine 88 MW, TYPE ABB Gas Turbine, 5 StagesGT Compressor 18 STAGE Axial Flow (TYPE VA 140 18)
Combustion Chamber Single Silo Type
Burner Single Stage Dual Fired
Air I ntake F il ter T ype Self Cleaning Tenekay Cartridges
Bypass Stack Vertical 25M High
WHRB Double Drum, Unifired, Assisted
Circulation TypeWH RB Steam Parameter s Pressur
e
Flow Temperature
HP 62.7 BAR 163 T/HR 485 ° C
LP 5.5 BAR 39.1 T/HR 207 ° C
Steam Turbin e 149 MW, Tandem Compounded Double
Exhaust, Condensing Type, Single Flow
Horizontal 25 Stage HP Turbine and 2X6Stage LP Turbine
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Condenser 2 Pass Surface Condenser with Stainless
Steel Tubes, Total Cooling Area 13988
M2
Cooling System for Condenser Open Cycle/Closed Cycle
Cooling Tower Type Induced Draft Cells
Cooli ng Water Pump 3X50% 15330 M3/HR each at 11.5 MWC
Range of Cooling 10 ° C
DM Water Plant 2 Streams each of 100% capacity to cater
to all 3 Boilers
Net Plant Output (STAGE-I ) 413 MW
Table 3.1: Sali ent F eatur es of Gas Tu rbin e
F igur e 3.1: Gas Tur bine at Anta
3.3. Generation Process
In Combined Cycle Gas Plant integrate two power conversion cycles, which are:1. Gas Turbine Plant (Bratyon Cycle) – Efficiency 34%
2. Steam Plant (Rankine Cycle) – Efficiency 35%
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3.Overall combined cycle plant efficiency is 49%.
3.4. Gas Turbine Plant
Gas turbine plants can use a variety of fuels – solid, liquid and gas. Natural gas which
has 80 % methane and small fractions of other gases is very widely used in plants
situated near 19
the gas fields. This is especially so for the plants used for auxiliary power generation
in oil fields. Present day gas turbine plants generally use natural gas and liquid
petroleum fuels.
F igur e 3.2 L ayout of Gas Tu rbine Plant
3.4.1. Gas Turbine Plant Equipments
1. Air-intake system2. Compressor
3.Combustion Chamber
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4. Gas Turbine
5. Gas Generator
3.4.2. Working of gas Turbine Plant Equipments
Air Intake System:
Compressor:
There are two types of compressors, the axial-flow compressor and the centrifugal –
or radial-flow compressor. Most power plant compressors are axial-flow compressors.
The object of a good compressor design is to obtain the most air through a given
diameter.
The compressor is made up of rotating blades on discs and stationary vanes that direct
the air to the next row of blades. The first stage compressor rotor blades accelerate the
air towards their trailing edges and towards the first stage vanes. The first stage vanes
slow the air down and direct it towards the second stage compressor rotor blades, and
so on through the compressor rotor stages (each stage is one rotating stage and one
stationary stage). The compressed air temperature is 1005 degree C.
Combustion Chamber:
Combustion is the chemical combination of a substance with certain elements, usually
oxygen, accompanied by the production of a high temperature or transfer of heat. The
function of the combustion chamber is to accept the air from the compressor and to
deliver it to the turbine at the required temperature, ideally with no loss of pressure.
Essentially, it is a direct-fired air heater in which fuel is burned with less than one-
third of the air after which the combustion products are then mixed with the remaining
air.
Gas Turbine (Brayton Cycle):
The Brayton cycle is used for gas turbines only where both the compression andexpansion processes take place in rotating machinery. The two major application
areas of gas-turbine engines are aircraft propulsion and electric power generation.
Gas turbines are used as stationary power plants to generate electricity as stand-alone
units or in conjunction with steam power plants on the high-temperature side. In these
plants, the exhaust gases serve as a heat source for the steam. Steam power plants are
considered external-combustion engines, in which the combustion takes place outside
the engine. The thermal energy released during this process is then transferred to thesteam as heat.
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Gas Generator
Gas generator’ s shaft is connected with gas turbine’ s shaft, by rotation of turbine
generator’ s shaft rotates and then energy is generated and fed to switchyard through
power transformer.
Exhaust Module
The gas turbine’ s hot gases exit via the exhaust section or module. Structurally, this
section supports the power turbine and rear end of the rotor shaft. The exhaust case
typically has an inner and outer housing. Hollow struts locate its position. The inner
housing typically has a cone shape or cover that encloses a chamber for cooling the
thrust bearing at the end of the shaft.
3.4.3 Other Gas Turbine System
Cooling System
Air for cooling the hot sections of the turbine are drawn (bleed air) from various
stages in the compressor. Mostly air is used for cooling, even if they have a combined
cycle operation.
Bearing and Lubrication System
Basically, sleeve bearings locate the turbine modules concentrically around the
shaft(s) during operation and when the turbine is not running, they provide the rotor
with support. The thrust developed by the overall rotor is absorbed by thrust bearings
at the end of the rotor. Oil flow to the bearings is regulated. The bearings in the hot
section require far more oil flow than those in the cooler compressor section.
Thermocouples or RTDs measure oil flow temperature. Sudden temperature rises in
the oil trigger an alarm or shutdown.
3.4.4. Gas Plant Silent Features
Make ABB-1
Type 13D2
On N atural Gas Output is 89.25 MW
On Naphtha Output is 86.03 MW
Gas Turbin e Type TA140 05
No. of stages 5Di rection of rotation seen i n di rection of Clockwise
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gas fl ow
Speed 3000 RPM
Gas inl et temperatur e 1005 ° C
Combustion Chamber Pressur e 11.6 Bar
Table 3.2: Detail of Gas Plan t
3.5. Steam Plant
3.5.1. Principle of Steam Plant
The hot exhaust gas exits from gas turbine and then passes through the Waste Heat
Recovery Boiler (WHRB). WHRB filled with high purity water. The hot exhausted
gas coming from the turbines passes through these tube bundles, which act like a
radiator, boiling the water inside the tubes and turning that water into steam. The
steam is fed to the turbine and energy is generated to supply.
F igu re 3.3 Waste Heat Recovery Boi ler
3.5.2 Steam Turbine (Rankine Cycle)
Process 1-2: Water from the condenser at low pressure is pumped into the boiler at high
pressure. This process is reversible adiabatic.
Process 2-3: Water is converted into steam at constant pressure by the addition of heat in the
boiler.Process 3-4: Reversible adiabatic expansion of steam in the steam turbine.
Process 4-1: Steam is condensate into water and feed to the boiler
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3.5.3 Waste Heat Recovery Boiler
Anta combined cycle power plant also known as Waste Heat Recovery Boiler (WHRB) plant,
which are of non-fired, dual pressure and forced circulation type. The boiler has two different
water/steam cycles known as high-pressure system and low pressure system.
Components of WHRB
The main components of WHRB can be divided into following categories:
LP Economizer
LP Drum and Evaporator
LP Super-heater
HP Economizer
HP Drum and Evaporator
HP Super-heater
LP Economizer
In economizer the flue gas heats up the feed water. After the economizer the feed water
enters the LP evaporators and then to LP drum boiler.
LP Super-Heater
The steam, leaving at the top of the LP Drum is heated by flue gas in super heater where it
reaches the end temperature about 220 degree C.
HP Economizer
The HP economizer coils are in two parts is just below the LP economizer and other part is
below LP super-heater and both the coils are connected in series.
HP Boiler Drum and Evaporator
The feed water in the HP boiler is pumped through the evaporator by means of 2x100% HP
circulation pumps.HP Super-Heater
The HP super heater consists of two parts with a spry attemperators them. This configuration
allows the temperature control of the superheated steam.
Condensate Pre-Heater
The main condensate is pumped by condensate extraction pumps (CEPs) to feed the water
tank. Before entering the feed tank the condensate is passed through the condensate pre-
heaters, which are situated at the tail end of the WHRBs and heated by the flue gas to achievethe highest cycle efficiency.
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TURBO GENERATORS
The Anta GPP consists of one module consisting of three gas turbine generators and one
steam turbine generator. Each turbo generator unit is a three phases, two pole cylindrical rotor
type machine directly connected to the steam / gas turbine, rotating at 3000 rpm. Generators
have the following main technical parameters.
Gas turbine generators Steam turbine generators
Rated output 97.5 MVA 191.5 MVA
Rated voltage 10.5 KV 15.75 KV
Rated power factor 0.8 0.8
Rated frequency 50 Hz 50 Hz
The machine is capable of delivering continuously its output within a voltage variation of
±5% and frequency variation of +3% to -5%. Generator is of Horizontal shaft air cooled type.
Air flows in a closed circuit and is cooled by air to water heat exchangers.
Waste heat recovery boil er
EMERGENCY DIESEL GENERATOR SET:
ENGINE
Number of cylinder : 12
Cylinder configuration : Vee-Form
Operating process : Four stroke
Combustion Process : Direct Injection
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Exhaust turbo charging : Yes
Cylinder size : Dia. 240 mm x L 280 mm
Standard Output : 2400 KW
Rated speed : 1000 RPM
Compression Ratio : 11.59 mm
Fuel consumption at full load : 210 g/KWh
Requirement of Air Intake : 17100 M3/Hr
GENERATOR
Output capacity : 2875 KVA
Nominal Voltage : 6600 Volt
Nominal Current : 263 Amp.
Nominal excitation current : 80 Amp.
Nominal excitation voltage : 100 V
Cooling air requirement : 21.3 M3/H
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CHAPTER 4
4. INTRODUCTION TO 220KV SWITCHYARD
4.1. Introduction
There are two types of substations: (1) Substation and (2) Switchyard
F igur e 4.1: Switchyard at NTPC Anta
4.1.1. Substations
A substation contains a transformer, which steps-up or steps-down power voltages, according
to the end-use purpose and destination. These transformers emit a low humming sound, and
in built-up residential areas, some manufacturing company’s transformers are primarily
contained within a cement sound enclosure to minimize noise.
4.1.2. Switchyards
Switchyard is considered as the HEART of the Power Plant. Power generated can be worthy
only if it is successfully transmitted and received by its consumers. Switchyard plays a very
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important role as a junction between the generation and transmission. It is a junction, which
carries the generated power to its destination (i.e. consumers).
Switchyard is basically a yard or an open area where many different kinds of equipments are
located (isolator, circuit breaker etc.), responsible for connecting & disconnecting the
transmission line as per requirement (e.g. any fault condition).
Power transmission is done at a higher voltage. (Higher transmission voltage reduces
transmission losses resulting in higher utilization of generating capacity and optimizes the
resource required for capacity addition.).
Therefore, the power generated by the gas generator of 1 to 3 units is 10.5 KV and by the
steam generator of 1 unit is 17.75 KV which is stepped-up to 220 KV by the Generating
transformer & then transmitted to switchyard.
In NTPC Anta there is only one switchyard i.e. 220 KV switchyard.
4.2. Types of Switchyard
There are three types of switchyards:
(1) Conventional Air Insulated Switchyard
(2) Gas Insulated Switchyard
(3) Air Insulated Switchyard
At NTPC Anta 220 KV switchyard is of type Conventional Air insulated Switchyard. There
are 12 bays in 220KV switchyard. A Bay is basically a way for the incoming power from
generator as well as outgoing power for distribution.
4.3. Salient features of 220 KV switchyard at NTPC Anta
4.3.1. Tasks of Switchyard
Delivers electrical power via outgoing transmission lines to various substations.
Protection of transmission system,
controlling the exchange of power,
Maintain the system frequency within the targeted levels,
Determination of power transfer through transmission line,
Fault analysis and subsequent improvements and
Communication
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F igur e 5.1: L ayout of Double Bus Bar Scheme
5.1.4. Double Bus Bar with Transfer Bus Scheme
This system has additional flexibility for operation.
We can shut down one breaker without interrupting the transmission line.
It is used for critical 220 KV substations.
F igur e 5.2: Double Bus Bar wi th T ransfer B us Scheme
5.1.5 One and Half Bus System
In this system three breakers are used for two circuits.
The loads are automatically transferred to healthy bus from fault bus without
interruption of circuit.
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It is important for 400 KV, where higher flexibility is required.
At NTPC Anta 220 KV Switchyard Double Main Bus and Transfer Bus Sc heme is
adopted.
5.2. Insulators These provide insulation between line conductors and supports and thus prevent the
leakage of current from conductors to earth.
F igur e 5.3 Strain I nsulator
F igur e 5.4: Suspension I nsulator
Material used for insulators:
Ceramic (Porcelain, Steatite)
Glass
Synthetic Resins
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5.4. Earthing Switch (E/S)
Earth switch is mounted on the isolator base on the line side or breaker side
depending upon the position of the isolator.
The earth switch usually comprises of a vertical break switch arm with the contact,which engages with the isolator contact on the line side.
Specification of used Isolators with and without E/S at NTPC Anta
Isolator (With Single E/S)
Make S & S Madras
No. of Provided 10Type RC 300 Horizontal Centre Break
Rating 245 kv, 1250 A
No. of Poles 3
Rated SC with stand
Current
31.5 kA, 1 Sec.
Table 5.1: Details of I solator s (with E/s)
Isolator (without E/S)
Make S & S Madras
No. of Provided 10
Type RC 300 Horizontal Centre Break, Tandem
Rating 245 kv, 1250 A No. of Poles 3
Rated SC with stand Current . 31.5 kA, 1 Sec
Table 5.2: Detail s of I solator s (without E/S)
5.5. Clamps and Connectors
There are different types of clamps and connectors used in switchyard for different purposeslike to connect the two conductors, to take tapping etc.
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5.6. Conductors and Accessories
Conductor consists of several strands wound in layers spiralled along the length of
conductor.
The total no. of individual strands “N” is given by
N=3n^2+3n+1, where N = no. of layers
Diameter of conductor = (2n+1)*d, where d= diameter of strand
F igur e 5.6: ACSR Conductor
Types of Conductors used are:
AAAC – All Aluminum Alloy Conductors
ACSR- Aluminum Conductor Steel Reinforced
AACSR- Aluminum Alloy Conductor Steel Reinforced
5.7. Circuit Breaker
A circuit breaker is an automatically-operated electrical switch designed to protect an
electrical circuit from damage caused by any disturbance in power system. Its function is to
interrupt continuity, to immediately discontinue electrical flow.
It can be used in off-load as well as on-load condition. When a circuit breaker is operated by
sending an impulse through relay, C.B. contact is made or broken accordingly. During this
making and breaking, an arc is produced which has to be quenched; this is done by air, oil,
SF6 gas etc.
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F igur e 5.7: SF 6 Cir cuit Br eaker
Features of Circuit Breakers
Superior Interrupting Capability
Low Operation Noise
Simple Construction and Compact Size
Easy Installation and Maintenance
High safetyDepending on the arc quenching medium being used C.B.s can be categorized into various
types. In NTPC Anta 220 KV switchyard only one type is being used:-
ACB (Air break circuit breaker):- operated as well as arc quenched through air.
BOCB (Bulk oil circuit breaker):- arc quenching done through oil (Aerosol fluid oil).
MOCB (Minimum oil circuit breaker):- arc quenching done through oil (Aerosol fluid
oil).
ABCB (Air Blast Circuit Breaker):- arc quenching done by blast of air
SF6 circuit breaker: - arc quenching done through SF6 gas.
Hydraulic operated SF6 circuit breaker is the most efficient due to following reasons:-
1. Less maintenance.
2. Arc quenching capability of SF6 gas is more effective than air.
3. Heat transfer capacity is better in this C.B.
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Specification of Circuit Breaker
Circuit breaker SF6
Make ABB Germany-10 Nos ABB
India- 1 No
Type ELF SL-5-2 and ELF SL-4-1
Rating 245/220 kv,2000 A
Breaking Capacity 40 kv
Insulation Level 1050 kv (Peak)
No. of Breaks per pole Two
Type of Operating Mechanism Closing : Spring, Opening :
Hydraulic
Gas Pressure 7 Kg/cm2
Closing time 70m Sec.
Opening time 20 m Sec.
Table 5.3: Specifi cation of Ci rcui t Br eaker
5.8. Instrument Transformer
These are used in measuring voltage and current in electrical power system and for power
system protection and control.
Types of Instrument Transformer
1. Current Transformer
2. Potential Transformer (CVT Type Transformer used)
5.8.1. Current Transformer
The current transformer is a step up transformer; it means current is stepped down to a very
low value (generally 1 or 5 A) so that it can be used for measuring and protection purposes.
C.T is designed in such a way its Core Material could give high accuracy with low saturation
factor. Core Material is generally made of CRGO Silicon steel. For very low loss
characteristics, μ material (Alloy of Ni -Fe) is used.
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F igur e 5.8: Connection of CT
Current Transformer is used for basically two major functions: -
1. Metering which means current measurement.
2. Protection such as:
Over current protection
Overload earth fault protection
Bus-bar Protection
Bus Differential Protection
CT is typically described by its current ratio from primary to secondary. There is not more
difference between 220KV and 400 KV CT, only current ratio differs.
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Specification of Current Transformer Current Transformer
Make ABB India
No. of Provided 30 Nos (1200-600/1A), 3 No (2000-
1000/1)
Type TMBR
Rating 245 kv, 1245 A
No. of Cores 5
Table 5.4: Details of CT
5.8.2. Capacitive Voltage Transformer
It is a step down transformer, which step down the high voltage to a lower value that can be
measured using the measuring instruments. The CVT are connected between phases and
ground in parallel to the circuit. The other most important function of C.V.T is that it blocks
power frequency of 50Hz and allows the flow of carrier frequency for communication.
F igur e .5.9: CVT
Protection of CVT
1. It can be continuously operated at 1.2 times the rated voltage.
2. Short circuit on the secondary side of a transformer can lead to complete damage of the
transformer.
3. Fuses are used in the secondary side to protect the transformer against faulty switching and
defective earthing.
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5.8.3. Potential Transformer
F igur e 5.10: Potential Tr ansfor mer
Potential transformers are used to operate voltmeters, the potential coils of watt meters and
relays from high voltage lines. The primary windings of the transformers are connected
across the line carrying the voltage to be measured and the voltage circuit is connected across
the secondary winding.
5.9. Surge Arrestor
A surge arrestor is electric equipment used in substations and switch yards. The surge arrester
is used to protect the substation equipment from surges caused by lightning or by sudden
switching. The Surge Arrester consists of spark gap in series with non- linear resistor. This
means that the surge arrestor has high resistance at the operating voltage and low resistance
as the voltage increases. The length of gap is set that normal line voltage is not enough to
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cause an arc. Thus when lightning strikes the overhead conductors in a substation, the arrestor
acts like a conductor and discharge the surge to the ground.
Surge arrestors are usually constructed of MOA (Metal Oxide Arrester) .
Zinc oxide is a widely used non-linear resistor. The zinc oxide is the form of blocks which
are stacked inside the arrestor. It is well accepted as voltage clippers for effective protection
against over voltages. The striking aspects of this arrestor are its simplicity of construction.
F igur e 5.11: L ightnin g Ar rester
Lightning arrestor on its continuous operation drives a small amount of driving current
usually of magnitude 0.1 to 0.8 mA. For monitoring this leakage current we use a surgemonitor as these leakage current increases with time which indicates the aging of arrestor.
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Specification of Lightning Arrester in NTPC Anta
Make WSI
No. of Provided 27
Type CPL-II, Heavy duty Station class
Rating 198 kv, 11 kA
Minimum discharge Capacity 5 kj/kv
Table 5.6: Specifi cation of L ightn in g Arr ester i n NTPC Anta
5.9.1. Arcing HornsArcing horns are used for protection of insulators in case of high voltage, which it cannot
withstand. There are two metal rods fitted on the top most and bottom most parts of the
insulator.
During high voltage insulator can’t resist, and crack may be developed. In order to avoid
these arcing horns are provided. Arcing Horns conduct the high voltage to the ground and
protect the insulator.
5.9.2. Ground (Earth) Wires
In an overhead power line, ground (earth) wires are wires that run above the live phase
conductors.
Since lightning caused damage to power equipment, as well as to that of the end users. So by
the use of proper ground (earth) wires above the normal conductors make it very unlikely for
lightning to hit the transmission lines directly. Reliability of transmission lines increases
greatly by the use of ground wires.
5.10. Earthing System
Earthing is to be provided in substations due to following reasons:
The object of earthing is to maintain a low potential on any object.
To provide a means to carry electric current into the earth under normal and fault
conditions, without exceeding any operating and equipment limits or adversely
affecting continuity of service.
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To assure that a person in the vicinity of grounded facilities is not exposed to the
danger of electric shock.
Following basic require are to be satisfied so as to ensure a proper earthing system:
The earth resistance for the switchyard area should be lower than a certain limiting
value in order to ensure that a safe potential gradient is maintained in the switchyard
area and protective relay equipment operate satisfactorily. For major switchyards and
substations in India this limiting value of earth resistance is to be taken less than 0.5
ohm.
The grounding conductor material should be capable of carrying the maximum earth
fault current without over-heating and mechanical damage.
All metallic objects which do not carry current and installed in the substation such asstructures, parts of electrical equipments, fences, armouring and sheaths of low
voltage power and control cables should be connected to the earthing electrode
system.
The design of ground conductor should take care of the effect of corrosion for the
total life span of the plant.
5.11. Wave Trap
Wave Trap is used to trap the high carrier frequency of 20Hz to 20 KHz and above and allow
the flow of power frequency (50 Hz). High frequencies also get generated due to capacitance
to earth in long transmission lines. The basic principle of wave trap is that it has low
inductance (2 Henry) & negligible resistance, thus it offers high impedance to carrier
frequency whereas very low impedance to power frequency hence allowing it to flow in the
station.
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F igur e 5.12: Wave Tr ap in switchyard
Generally there are two class of line trap depending upon the value of inductance. Inductance
value may be of 1.0 mH or 0.5 mH.
Specification of Wave Trap used at NTPC Anta
Make WSI
Nos Provided 6Rating 0.5 mH, 1250 A, 220 kv
Table 5.7: Specif ication of Wave Tr ap used at NT PC Anta
5.12. PLCC (Power Line Carrier Communication)
As the name suggests, P.L.C.C. is basically a method in which the line used for power
transmission is also being used for communication.
P.L.C.C is employed for performing following two functions:
1. Communication purposes.
2. Protection
5.12.1. Communication Purpose
There are two types of electrical frequency which flow in a line- 50Hz power signal & 20
KHz of carrier signal. In order to isolate these two frequencies (so that they do not hinder
each other) tapping of the frequencies is done as per the requirement.
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Since in the buses and bays we need only power frequency, wave traps are being used to
block high frequency carrier signals. C.V.T. blocks the power frequencies and due to the
capacitance present it allows the high frequency carrier signals to pass through co-axial
cables.
5.12.2. Protection
Transmission line between two sub-stations is bi-directional. When a fault occurs and a trip
command is given at one end, the breaker gets opened. Now the other end breaker should also
be opened to completely isolate the line from supply. For this the other end should also give
the trip command. This is when the P.L.C.C. comes into play. From the P.L.C.C. room
present at the tripping end along with the carrier signal, a signal of a lesser frequency is
superimposed and sent to the P.L.C.C. room present at the other end. Now this will be
demodulated and the other end will come to know that tripping has occurred.
F igur e 5.13: PL CC Schematic Di agram
Now it will give a command, which will energize the relay, contact will be made and the
breaker will operate.
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Specification of PLCC at NTPC Anta
Batter ies for PL CC System
Make Exide Ltd.
Type Lead acid Cell, 2 Volts/Cell
Rating 48V, 300 AH
Battery Charger (PLCC)
Make Chhabi
Nos. Provided 1 (Normal), 1 (Reserve)
PLCC E quipments & Panel
Make ABB India
Nos Provided 8
Table 5.8 Detail s of PL CC at NTPC An ta
5.13. Control and Relay Panel
Control panel mostly consists of meters and protective relays. The meters include ammeter,
voltmeter, wattmeter, energy meter etc. The relays include over voltage relay, over current
relay, over frequency relay, under voltage relay, under frequency relay, earth fault relay,
master trip, distance relays. Auxiliary relay and transformer relays like OLTC out of step,
winding temperature alarm, oil temperature alarm. The trip indicators included are CB SF6
gas density low, CB Air pressure low, VT fuse fail alarm, CB pole disc trip, carrier signal
received, back up protection, auto reclose lock out, control DC supply fails, distance
protection , carrier out of service, distance protection trip etc.
AUTOMATION
Early electrical substations required manual switching or adjustment of equipment, and
manual collection of data for load, energy consumption, and abnormal events. As the
complexity of distribution networks grew, it became economically necessary to automate
supervision and control of substations from a centrally attended point, to allow overall
coordination in case of emergencies and to reduce operating costs. Early efforts to remote
control substations used dedicated communication wires, often run alongside power circuits.
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Conclusion
The training at grid substation was very helpful. It has improved my theoretical concepts of
electrical power transmission and distribution. Protection of various apparatus was a great
thing. Maintenance of transformer, circuit breaker, isolator, insulator, bus bar etc was
observable.
I had a chance to see the remote control of the equipments from control room itself, which
was very interesting. So the training was more than hope to me and helped me to understand
about power system more
I feel I got the maximum out of that experience. Also I learnt the way of work in an
organization, the importance of being punctual, the importance of maximum commitment,
and the importance of team spirit. I have learnt many things in this 45 days training session.
In my opinion, I have gained lots of knowledge and experience needed to be successful in a
great engineering challenge, as in my opinion, Engineering is after all a Challenge, and not a
Job.
The main objective of the industrial training is to provide an opportunity to undergraduates to
identify, observe and practice how engineering is applicable in the real industry. It is not only
to get experience on technical practices but also to observe management practices and tointeract with fellow workers. It is easy to work with sophisticated machines, but not with
people. The only chance that an undergraduate has to have this experience is the industrial
training period.
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REFERENCES
Books
1. Anderson 1987 “Transmission Line Reference Book”, Second E dition Substations
Committee
2. Geri. A, “Behavior of grounding system excited by high impulse current: the model
and its validation,” IEEE Trans, Power Deliver, 1999.
3. Nagrath, I.J. and D.P.kothari, Electric Machines, Tata McGraw-Hill , New Delhi,
Third Edition, 2004
4. Kiessling, Friedrich; Nefzger, Peter; Nolasco, Joao F.; Kaintzyk, Ulf (2003),
Overhead Power Lines , Springer, ISBN 3540002979
5. Wadhwa, C.L. (2006), Electrical Power Systems , New Age Publishers , ISBN 978-
8122417739
6. Kiessling, Friedrich (2001), High Voltage Engineering and Testing , IET, ISBN
0852967756
7. Harlow, James (2004). Electric Power Transformer Engineering . CRC Press. ISBN
0-8493-1704-5.
8. Standards
9. IEEE Std 998- 1996 “Guide for Direct Lightning Stroke Shielding of Substation”,IEEE Working Group D5
10. IEEE Std C37.91-2000 IEEE Guide for Protective Relay Applications to Power
Transformers
11. Internet
12. Three-phase transformer circuits from All About Circuits
13. J.Edwards and T.K Saha, Power flow in transformers via the Poynting
vector (http://www.itee.uq.edu.aq/~aupec/aupec00/edwards00.pdf)PDF (264 KB)
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