report on rgtpp jaisalmer

ACERC/DOEE/2016-17/PTS/1

CHAPTER: 1

INTRODUCTION

RGTPP is located near Ramgarh Town district head quarter, Jaisalmer (Rajasthan), which

is largest district of the state. Its installed capacity at about 60 km from is 270 MW. And

this plant is located in largest state of India, based on area

There was problem in maintaining desired quality standards in electric supply to Jaisalmer

on account of excess losses because of longer transmission lines. To rectify above problem

and to utilize available natural gas in this area RGTPP was established in this border

district whose existing capacity is 270 MW.

Seeing the increasing demand of electricity in this region for various purposes like for

providing drinking water in desert area, flood lighting on INDO-PAK Border fencing etc..,

state Govt. found it essential to raise= the capacity of RGTPP and therefore Rajasthan

Vidyut Utpadan Nigam Ltd. established here two more units in second phase of the

project. In second phase, one gas turbine of 75 MW capacities and one steam turbine of

37.5 MW capacities were installed.

Fig No. 1.1-Ramgarh Gas Thermal Power Plant Entrance


Figure 1.2: Power Plant View

1.1 First Unit

Necessary equipment for this power plant was supplied by Bharat Heavy Electrical Ltd.

(BHEL), and building construction was carried out by Rajasthan State Bridge Construction

Corporation. This unit is capable to generate power using both gas and diesel. In power

plant 12 underground tanks are constructed for storage of diesel having total capacity of

2520KLt. In This Stage Gas Turbine (GT-1) Is Used Which Includes Unit of 75 MW and

steam turbine (ST-1) is used which include unit of 37.5 MW.


1.2 Second Unit

First unit of this power plant is being operated by open cycle system, resulting in higher

cost on electricity generation. Reduction in cost is only possible when first unit is operated

on Combined Cycle System. So, under expansion program of this project, work of

installation of a gas and steam turbine is taken in hand. In this system, electricity will be

generated by a steam turbine utilizing heat obtained from exhaust of gas turbines through a

Heat Recovery Boiler. Thus, no additional fuel will be required for operating Steam

Turbine.

Under stage-II, one Gas Turbine Unit (110 MW) was commissioned and synchronized

with the grid on June 2010 The Steam Turbine Unit (50 MW) was also commissioned and

synchronized with the grid on June 2010 and thus the plant has been made operational in

combined cycle mode with a total capacity of 270 MW.

1.3 Availability of Water

Requirement of water for power plant is supplied through Sagar Mal Gopa branch of

Indira Gandhi Nahar Project. (IGNP) for this a 27 KM Long , 5.4 cusec capacity pipe line

is laid from RD-190 of Sagar Mal Gopa Branch to power plant & another pipe line from

RD-200. For ensuring proper electric supply requirements, a Sub-station of capacity

2X250KVA, 33/0.4KV, and a pumping station has been established at RD-190 in addition

to construction of a water storage tank of capacity 77000m3 at power plant.

1.4 Electricity Transmission System

To ensure efficient transmission of electricity generated in the power plant, a 215km long

Ramgarh-Jaisalmer-Barmer line & 165km Ramgarh-Pokaran of 132 KV has been laid.

1.5 Expected System Operation

In spite of unfavorable geographical conditions and supply of gas of lower quality than

expectation, expected electricity is being generated in this power plant.

The details of total energy generated from this power station during years are as under


YEARS ENERGY GENERATED(MU)

1999-00 228

2000-01s 229

2001-02 120

2002-03 221

2003-04 238

2004-05 361.13

2005-06 435.62

2006-07 404.14

2007-08 414.11

2008-09 348.67

2009-10 424.11

2010-11 430.15

2011-12 431.98

Table no.1.1: Total Energy Generated

1.6 Gas Transportation System

ONGC and IOCL are engaged in exploration of oil and natural gas deposits in western

Rajasthan. Gas Authority Of India Ltd. (GAIL) laid down 12”diameter and 35 km long

pipe line for supply of gas from Gamnewala based gas collection plant to Ramgarh, which

has been further extended up to Dandewala gas field of Oil India Ltd. Total distance of

Dandewala Terminal, is approximately 67 km from Ramgarh Terminal. This pipe line is

being maintained by GAIL.

Gas, which is use in plant, is mixture of different gas. Percentage of gas is as follows:-


Table no.1.2: Gas (full) Component

GAS PERCENTAGE

NITROGEN 31.9064 %

METHANE 48.5668 %

CARBON DIOXIDE 18.8793 %

ETHAN 0.5009 %

PROPANE 0.0333 %

ISO-BUTANE 0.0285 %

N-BUTANE 0.0513 %

ISO-PENANE 0.0185 %

N-PENANE 0.0130 %

HEXANE 0.0000 %

TOTAL 100 %


CHAPTER: 2

POWER PLANT CYCLE

Ramgarh Gas thermal power station is Combined Cycle power station, which is largest

district of the state. Its installed capacity at about 60 km from is 270 MW. And this plant is

located in largest state of India, based on area

2.1 Open Cycle

When Gas Turbine (GT) exhaust is diverted directly into the atmosphere due to no

provision of HRSG (Heat Recovery Steam Generator) or non-availability of HRSG then it

is called as GT is running in open cycle. In open cycle as gas turbine high exhaust gas is

not utilized for heat transfer in boiler so its efficiency will come down.

2.2 Combined Cycle

When Gas Turbine exhaust is diverted to HRSG in which high temperature Gas Turbine

exhaust gas passes through HP Super Heater, HP Evaporator, HP Economizer, LP

Evaporator, LP Economizer, and Condenser Preheated (CPH) thus heat of gas turbine

exhaust gas absorbed by above series of bank located inside the HRSG and temperature of

gas turbine exhaust which is about 570 degree C will come down to 135 degree C.

By utilizing the heat of gas turbine exhaust HRSG (Boiler) generates Steam which is used

to run Steam Turbine Generator (STG).

Thus we can generate an additional power (about 50 % of the gas turbine generation) in

Steam Turbine Generator without any extra fuel cost. Thus we can get 30% extra

efficiency by running the gas turbine in combined cycle.

As gas turbine is operated on Brayton Cycle principle and Steam Turbine is rotated on

Rankine cycle principle that is why it is called Combined Cycle.

2.3 Advantages of Combined Cycle Process

Decreases in capital cost per mw installed.

High overall efficiency i.e. 48%.

Compact in size.

Low main power required for its operation and maintenance.


Low water requirement.

Pollution free atmosphere and clean works place.

Low installation time.

High reliability and flexibility of the plant.

2.4 Brayton Cycle

Figure 2.1: Brayton Cycle

FUEL COMBUSTION

CHAMBER

GENERATOR COMPRESSOR TURBINE

TURBINE EXHAUST AIR


2.5 Rankine Cycle

Fig no 2.2: Rankine Cycle

STEAM

GAS

TURBINE

EXHAUST

TURBINE BOILER

FEEDWATER

CONDENSATE


CHAPTER: 3

BRIEF INTRODUCTION OF PLANT OPERATION

At RGTPP gas to the turbines is being supplied through GAIL terminal from oil wells of

ONGC and OIL, which are attached to discover oil and natural gas recourses in Western

Rajasthan. The quantity of the gas is 9.5 Lac SCM per day. From GAIL Terminal gas is

supplied to Gas Booster Compressor (GBC motor) at pressure of 10-15kg/cm2 and

quantity of gas is 9.5 Lac SCM/day.

The work of the Gas Boost Compressor is to compress gas and to supply required pressure

of gas for power production to gas turbine. In compressing process by GBC the pressure of

the gas increases from 10-15kg/cm2 to 18-23kg/cm2. The output of the GBC motor is first

merged and then is divided further, before blowing into the Combustion Chamber. There

are two GBC motor in RGTPS, GT-1 and GT-2. The blowing pressure is 18-23 kg/cm2.

Combustion Chamber is a place where ignition of fuel mixed with air occurs with the help

of the sparkplugs, the voltage on both of the sparkplugs is 15000 V dc. On combustion, the

gas gets mixed with air then the gas will expand and air pressure will increases. This air

exhausts on the gas turbine buckets & nozzles and gas turbine starts to rotate. There are

two generators of 35.5 MW and 37.5 MW attached with GT-1 and GT-2 respectively,

mounted on the same shaft as the turbine. So GT-1 and GT-2 produces 35.5 and 37.5 MW

electricity respectively.

The exhaust of GT is flue gases. The temperature of flue gas is near about 500 degree C.

This exhaust may also be relieved into the atmosphere with the help of controlled valves.

But this exhaust is taken in use to produce electricity. So this power plant is called

Combined Cycle Power plant. This exhaust (flue gas) of the gas turbine is further passed

into the Heat Recovery Steam Generator (HRSG). It is a boiler. Water circulating in

drum is superheated with the help of flue gases. This superheated steam runs the Steam

Turbine Generator, so it is called unfired combined cycle.

The generator is mounted on the same shaft as of the steam turbine, produces 37.5 MW

electricity. The steam which is blowing on the gas turbine should be superheated.

Steam should be superheated so that-

1. No corrosion will be occur,

2. Enthalpy drop will be less.

Power generation is also done at low voltage because of the insulation problem.


If the power generation is done at high voltage then there are following disadvantages-

1. Losses will be more

2. Wire also may burn out

3. High insulation will be required which is very costly

Figure: 3.1 Operation of RGTP

AIET/DOEE/2016-17/PTS/11

CHAPTER: 4

GAS TURBINE

Turbine Equipment:

In this chapter we discuss about the gas turbine and its major equipment. There

are many components or equipment are available for making a turbine, in this

chapter we discuss some of them in detail:

4.1 Compressor

The atmosphere air is compressed to the 17 stage compressor and before it passes through the

filter. The compressor ratio is 10 and this air is routed to the combustors. The compressor

used in the plant is of rotatory type. The air at atmospheric pressure is drawn by the

compressor via the filter which removes the dust from the air. There are 396 no. of filters

connected in different rows. These filters are made up of cellulose fiber. The rotatory blades

of the compressor push the air between stationary blades to raise its pressure.

4.2 Combustors

The fuel (gas) is provided to ten equal flow lines, each terminating at a fuel nozzle centered

in the end plate of a ten separate combustion chamber and prior to being distributed to the

nozzles, the fuel is actually controlled at a rate consistent with the speed and load

requirements of gas turbine. The nozzle introduces the fuel into the combustion chambers

where it mixes with the combustion air and is ignited by the sparkplugs. At instant when fuel

is ignited in one combustion chamber, flame is propagated through connecting crossfire tubes

to all other combustion chambers.

4.3 Transition Pieces

The hot gases from the combustion chambers expand into the ten separate transition pieces

and from there to the three stage turbine section of the machine.

4.4 Turbine

There are three stages of the turbine and each consists of a row of fixed nozzles followed by a

row of rotating turbine buckets. In each nozzle row, the kinetic energy of the jet is increased


with an associated pressure drop and in each following row of a moving buckets, a portion of

the kinetic energy of the jet is absorbed as useful work on the turbine rotor.

4.5 Exhaust

After passing through the third stage buckets, the gases are directed into the exhaust hood

diffuser which contains a series of turning vanes to turn the gases from an axial direction to a

radial direction, thereby minimizing exhaust hood losses. The gases then pass into the

exhaust plenum and are introduced to atmosphere through the exhaust stack or to the

H.R.S.G.


CHAPTER: 5

GAS TURBINE SUPPORT SYSTEM AND ITS EQUIPMENTS

5.1 Starting System

In this chapter we discuss about gas turbine support system and their equipment:

5.1.1 Diesel Engine

Diesel engine/starting motor/Main generator with static frequency converter. Diesel or

starting motor with torque converter or main generator with SFC is used as a starting device

for gas turbine. We have Detroit make diesel engine of 590 HP for starting purpose.

5.1.2 Torque Converter

It transfers torque from DG to Gas Turbine. It is a hydraulic coupling which transfers torque

from zero speed to self-sustaining speed of Gas Turbine (i.e. about 60% speeds).

5.1.3 Accessory Gear Box

It accommodates following equipment:

Main lubricant Oil pump

Main hydraulic pump

Main fuel oil pump

Atomizing air compressor

5.1.4 Hydraulic Ratchet

It rotates the turbine shaft when gas turbine is on cool down. It also helps while break away

of Gas Turbine during starting. It consists of a ratchet mechanism operated by hydraulic

device. Oil is supplied by a DC driven positive displacement pump.

5.1.5 Jaw Clutch Mechanism

It transmits power from Diesel Engine or Ratchet Mechanism to Gas Turbine through Torque

Converter for starting of Gas turbine or at the time of ratcheting.

5.2 Lubricating Oil System

Major equipment of the system are-

5.2.1 Oil Reservoir:

The capacity is 3300 gallons. The total system requirement is 3500 gallons.


Lubricating Pump:

Main lube oil pump is accessory gear driven. Also for starting a/c power driven lube oil pump

of 175m head and 460gpm flow is provided. For emergency purpose DC pump of 91m head

and 250 GPM flow is provided. During emergency pump in service filter remain by pass.

5.2.2 Heat Exchanger:

Two coolers are provided for cooling oil each of 100% capacity.

5.2.3 Gas Skid:

The function of the gas conditioning skid is to supply gas to Gas Turbine free from

condensate and gas particles.

5.2.4 Scrubber:

The function of the scrubber is to remove condensate from gas by centrifugal action by the

use of no. parting plates within the scrubber itself. There is a provision of solenoid operated

drain valve for removal of condensate which is sensed by a level switch.

5.2.5 Filter:

The function of filter is to remove any foreign particles from the gas and to supply totally

clean gas. These filters are of cartridge type and replaceable if D P across the filter increases.

5.2.6 Pressure Control Valve:

The function of the pressure control valve is to regulate down steam pressure up to 22kg/cm2

if upstream pressure is more. This is the designed value for inlet the gas stop ratio control

valve.

5.2.8 Condensate Tank:

All the condensate collected at the bottom of the scrubber is routed to the tank through drain

piping. For this is a level controller on the scrubber which will operate on maximum and

minimum level scrubber.

5.3Air Intake System:

5.3.1 Filters:

There are 396 numbers of filters connected in different rows. These filters are made up of

cellulose fiber.


Fig No. 5.1-Filter

5.3.2 Filter Cleaning:

Reverse pulse self-cleaning system is provided for cleaning of these fibers. Processor air is

used for these pulsations. Each row is given reverse pulse at fixed time interval and in

predefined rotation.

5.3.3 Air Processing Unit:

The air from the compressor output is taken to finned tube to cool it and is passed through the

dryer for removing moisture.

5.4 Cooling and Sealing Air System:

Air for the bearing sealing is extracted from the 5th stage of the compressor. Centrifugal

removes dust and other foreign particles. Two centrifugal blowers are provided for turbine

shell cooling


5.4.1 Ventilating System:

Being a closed system, air circulation is provided by following ventilating fans in different

compartments:

1. Accessory and gas turbine compartment vent fan

2. Load gear compartment

3. Gas valve compartment vent fan

4. Load gear oil vapors fan

5.4.2 Gas Turbine and Compressor Cleaning System:

Compressor washing skid consists of:

a) Water tank with heaters,

b) Water pump,

c) Detergent pump,

d) Water wash valve (electrically operated).

Rice hopper is provided at compressor suction for solid compound cleaning of compressor.

5.4.3 Reducing Gear Box:

Gas turbine speed is 5100rpm, but generator speed is designed as 3000rpm, so reducing gear

box is provided to reduce speed to 3000 rpm.

5.5 H.R.S.G and Steam Turbine Equipment:

5.5.1 H.R.S.G:

HRSG is a horizontal, natural circulation, bid rum, dual pressure unfired water tube boiler. It

is designed to generate HP steam at 62kg/cm2 pressure and 483 degree C temperature with

59.9 t/ HR steam flow. LP steam is generated at 5 kg/cm2 pressure and at saturated

temperature with 10.9t/HR steam flow. These H.R.S.Gs are having facilities of HP and LP

bypass systems 100% for both the circuits to match the rated parameters(pressure and

temperature) while starting the H.R.S.Gs and to minimize the losses of water and heat while

shutting down the m/c. These are also useful when STG trips and to keep boiler in service.

Major equipment of recovery boilers are:

1) Super heater,

2) Evaporator (HP & LP),

3) Economizer (HP-1, 2 & LP)

4) Stack (height)


5.5.2 Steam Turbine:

The HP Steam Turbine is drawn from HP steam header of H.R.S.G 1&2. The HP steam

parameters of the HP steam are 60kg/cm2pressure and 480deg C temperature. The LP steam

to turbine is drawn from LP steam header of HRSG 1&2. The LP steam parameters of LP

steam are 4.3kg/cm2 pressure and 148 degree C temperature.

5.6 Condensate Circuit Equipment:

It consists of condensers, ejectors, extraction pumps, gland steam condenser.

5.6.1 Condenser:

It is a two pass condenser having 9084 no. of tubes having cooling surface area of 3070m2. It

has steam condensing capacity of 137t/HR, cooling water flow of 7050m3/hr.

5.6.2 Ejectors:

Two no. of two pass ejectors are provided each having a capacity of handiling15kg/HR dry

air 49kg/HR air-water vapor mixture. One starting ejector is also there of 220kg/HR of dry air

handling capacity at a suction pressure of 0.33 atmosphere.

5.6.3 Extraction pumps:

Two no. of pumps each of 100% capacity are used in the system. Each has a capacity of 95 m

head and 186m3/HR flow.

5.6.4 Gland Steam Condenser:

Steam leaking from turbine glands is used to raise the temperature of the condensate by GSC.

Two no. of fans are provided for extracting steam.

5.7 Feed Water Circuit

It consists of the feed water tank; HP & LP feed water pumps.

5.7.1 Feed Water Tank:

It is mounted at elevation of 9m so it provides a net positive suction head to the boilers feed

pumps. It also has a desecrator at the top of the tank for mechanical desertion of the feed

water.

5.7.2 HP Feed Pumps:

Three feed pumps of 50% duty are provided to feed h. p water to boiler. Each is a KSB make,

multistage pump with discharge head of 925m and 75m3/hr.


5.7.3 LP Feed Pumps

Three feed pumps of 50% duty are provided to feed l. p water to the boiler. Each is a Beacon

Water make, multistage pump with discharge head of 117m and 11.5m3/hr.

5.8 Common Support System for GT and ST:

5.8.1 CW and ACW systems:

There are three CW pumps each of 50% capacity of 23 head and 3850t/HR flow. They

circulate water in steam turbine condenser and ST oil cooler. There are three ACW pumps

each of 50% capacity of 34m head and 576t/HR flow. They circulate water in following gas

turbine auxiliaries:

A) Diesel engine,

B) Lubricant Oil coolers,

C) Generator air coolers.

It also circulates in feed pump bearing, coolers of AC plant, air compressors, ADUs and

boilers water sample coolers

5.8.2 Air Compressors:

Air is required for the following purposes:

a) For pneumatic operations of all control valves,

b) At different maintenance work places for cleaning,

c) If required it can be used for GT filter cleaning.

There are three parameters make horizontal, balanced opposed piston compressor each of

8.1kg/cm2 head and 253 Nm cu. /HR air flow. Air from the receiver tank is directed to air

drying unit to moister free.

5.8.3 Raw Water System:

Three no. of bore wells supply raw water to a water reservoir from which is transferred to

water treatment plant by use of raw water pumps each of 125t/HR flow capacity. Each bore

well is of 125 to 150t/HR flow capacity. Daily raw water consumption of the plant is around

4000t.

5.8.4 Laboratory:

Any power plant requires soft water and dematerialized water in large quantity. There are soft

water plant (cap 7.2 t/HR*2) which is used in the boiler water circuit. Apart from that, a

continuous watch is kept of water chemistry of HRSG water to keep its parameters (such as

ph and conductivity) within a specified range.


5.8.5 Fire Protection Systems:

It includes no. of water pumps, Halogen & CO2 bank, nozzle and piping network, flame and

smoke detectors and emulsifies. There are three types of water pumps:

a) HVWS pump,

b) Jockey pump.

5.8.6 Black Start D.G Set:

In the event of total power failure, GT can be started with the help of diesel generating set

(500 KVA, 680 Amp Max) which is capable of supplying power to the bare minimum

requirements of the auxiliaries of one gas turbine. Later, other auxiliaries can be started with

the help of running gas turbine.


CHAPTER: 6

CONSTRUCTIONAL DETAILS OF GAS TURBINE

6.1 Compressor Section:

The axial-flow compressor consists of the compressor rotor and the enclosing casing. The

inlet guide vanes, the seventeen stages of the rotor and stator balding and the two exit guide

vanes are included with in the compressor casing.

In the compressor, air is confined to the space between the rotor and stator balding where it is

compressed in stages by a series of alternate rotating (rotor) and stationary (stator) airfoil

shaped blades. The rotor blades supply the force needed to compress the air in each stage and

the stator blades guide the air so that it enters the following rotor stage at the proper angle

.The compressed air exits through the compressor discharge casing to the combustion

chambers. Air is exerted from the compressor for turbine cooling bearing sealing and, during

start-up, for pulsation control.

6.1.1 Rotor:

The compressor rotor is an assembly of fifteen wheels two stub shaft, through bolts, and the

compressor rotor bulkhead .The first stage rotor blades are mounted on the wheel portion of

the forward stub shaft.

6.1.2 Stator:

The stator (casing) area of the compressor section is composed of five major sections:

(1) Inlet Casing

(2) Inlet Guide Vanes

(3) Forward Compressor Casing

(4) Aft Compressor Casing

6.2 Combustion Section:

The combustion system is the reverse flow type and comprises ten combustion chambers with

liners, flow sleeves, transition pieces and crossfire tubes. Flame detectors, crossfire tubes,

fuel nozzles and spark plug igniters are also part of the complete system. Hot gases,

generated from the burning of fuel in the combustion chambers, are used to drive the

turbine.


6.2.1 Combustion Chambers:

Discharge air from the axial-flow compressor enters the combustion chambers from the

cavity at the center of the unit. The air flows upstream along the outside of the combustion

liner towards the 1 inner caps this air enters the combustion chamber reaction zone through

the fuel nozzle swirl tip(when fitted) and through metering holes in both the cap and liner

.When the nozzles supplied are not of the type fitted with a swirl tip, the combustion

chambers are fitted with a tabulator system.

The hot combustion gases from the reaction zone pass through a thermal soaking zone and

then into a dilution zone where additional air is mixed with a combustion gases. Metering

holes in the dilution zone allows the correct amount of air to enter and cool the gases to the

required temperature. Openings located along the length of the combustion liner and in the

liner cap provide a film of air for cooling the walls on the liner and cap. Transition pieces

direct the hot gases from the liners to the turbine nozzles.

The ten combustion chamber casings are identical with the exception of those fitted with

spark plugs or flame detectors.

6.2.2 Spark Plugs:

Combustion is initiated by means of high-voltage, retractable -electrode spark plugs installed

in two of the combustion chambers. This spring -injected and pressure -retracted plugs

receive their energy from ignition transformers. At the time of firing, a spark at one or both of

these plugs ignites the combustion gases in a chamber. The gases in the remaining chambers

are ignited by crossfire through the tubes that interconnect the reaction zones of the

remaining chambers.


COMPONENTS RATINGS

GAS PRESSURE ( kg/cm2 ) 22 kg/cm2

HYDRAULIC OIL PRESSURE ( kg/cm2 ) 80 kg/cm2

GENERATOR BEARING PRESSURE ( kg/cm2 ) 0.5 kg/cm2

RATIO VALVE GAS PRESSURE ( kg/cm2 ) 16 kg/cm2

LUBE OIL PRESSURE ( kg/cm2 ) 2 kg/cm2

GAS TEMPERATURE (degree C ) 120 degree C

LUBE OIL TANK TEMPERATURE (degree C ) 50-60 degree C

GENERATOR (rpm) 3000

GENERATOR TURBINE (rpm) 5000

GENERATING VOLTAGE( kilo volt ) 11KV

TURBINE (MW) 35.5 MW

Table No. 6.1: Gas Turbine-1 (GT-1)


COMPONENTS RATINGS

GAS PRESSURE ( kg/cm2 ) 22 kg/cm2

HYDRAULIC OIL PRESSURE ( kg/cm2 ) 80 kg/cm2

GENERATOR BEARING PRESSURE ( kg/cm2 ) 0.5 kg/cm2

RATIO VALVE GAS PRESSURE ( kg/cm2 ) 16 kg/cm2

LUBE OIL PRESSURE ( kg/cm2 ) 2 kg/cm2

GAS TEMPERATURE (degree C ) 120 degree C

LUBE OIL TANK TEMPERATURE (degree C ) 50-60 degree C

GENERATOR rpm 3000

GENERATOR TURBINE rpm 5000

GENERATING VOLTAGE ( kilo volt) 11KV

TURBINE MW 37.5 MW

Table No. 6.2: Gas Turbine-2 (GT-2)

6.3 STG (Steam Turbine Generator) 6.3.1 Turbine:

The function of the turbine is to drive the generator at a speed of 3000 rpm. The heat energy

of steam (enthalpy) is converted in mechanical energy as steam expands in turbine. Before

entering the main steam in turbine it passes through emergency stop valve and control valve

located at turbine floor, there are 53 stages in turbine, one stage consists of a set of fixed

blade mounted on inner casing and rotary blade mounted on turbine shaft. LP injection is

connected after 43 stages of turbine. The turbine shaft is supported by the front bearing

(Journal & thrust bearing) and the rear bearing (Journal bearing) .The axial thrust produced in

the moving blades is balanced by balancing drum located in the front side of turbine. The

residual thrust forces of turbine that have not been compensated by balancing piston are taken

up by the front thrust bearing .The rear bearing of turbine houses the oil hydraulic turning

device used for running the turbine on bearing gear. Turbine gland sealing is done to avoid

air entry initially at both gland ends at in running to seal the LP end gland. When turbine is

running sealing is done through turbine leak steam itself and balance steam flows to

condenser.


6.3.1.1 Turbine Oil System:

a) MOT:

MOT is located on 5m. It serves for storing the oil volume required for governing and

Lubrication system .Oil vapor in oil tank are vented out by an oil vapor exhaust fan installed

at the top of MOT. The MOT is provided with oil centrifuge inlet connection at bottom and

the oil centrifuge return is connected back to oil tank. The oil centrifuge cleans the oil stored

in MOT.

b) MOP:

Lubrication oil needed for turbine bearing, governing oil system and barring gear is supplied

by MOPs .The bearing Lubrication oil is supplied after cooler and duplex filter but governing

oil and barring gear oil flows directly from the MOP discharge header.

Discharge Pressure : 10.2kg/cm2

Flow : 150 m3

Motor rating : 55 KW, 93 A

Standby pump : 6.5 Kg/cm2

c) DC EOP:

In case of tripping /non availability of both MOPS ,DCEOP server for supplying oil for

bearing cooling .The emergency oil pump cuts in automatically when oil header falls below

0.9 Kg/cm2 in the event of further pressure fall in header, Oil shall be fed from an overhead

oil tank placed about 6.5 m over the turbine.

d) JOP:

In the case of startup and shut down, on barring gear it is necessary to supply the high oil to

lift the shafting system slightly so as to avoid metal to metal contact. Friction between shaft

and bearing for these purposes are two nos. JOPS are provided; one is AC-JOP and another is

DC-JOP.


Fig.No.6.1-Oil Cooling System

6.4 Heat Recovery Steam Generator (HRSG):

Two no. of HRSG Established one each for steam generation utilizing waste heat of exhaust

gases of GT1 GT2 respectively. HSRG is natural circulation Unfired Steam Generator Feed

water coming from BFP discharge passes through the tube bunches of different modules of

heat transfer surfaces and gets heated by gas turbine exhaust flowing in surrounding duct.

HRSG has nine heat transfer surfaces as mentioned below:

(i) High Pressure Super Heater

(ii) HP-evaporator including HP drum

(iii) HP-Economizer for preheating the feed water entering in drum. These are three in

numbers.

(iv) LP- Super Heater

(v) LP- Evaporator including LP drum

(vi) LP- Economizer

(vii) Condensate preheated (CPH) for heating condensate water before flowing to Deaerator.


Fig No.6.2-Power Plant View

COMPONENTS RATINGS QUANTITIES

HPBFP-1,2,3 425 Kw 3

LPBFP-1,2,3 22 Kw 3

HP DOSING PUMP(HP CIRCUIT) 0.75Kw 4

LP DOSING PUMP(LP CIRCUIT) 0.37Kw 4

DEARATOR 1

Table No. 6.3: HRSG -1 & 2


Fig No.6.3 -Water Tube Boiler

Figure No. 6.4-H.R.S.G

Gas Cycle in HRSG:

HP Super Heater HP Evaporator HP Eco III LPSH LP Evaporator HP Eco II

LP Eco HP Eco I CPH Chimney


6.5 Generator

The gas turbine is coupled with the generator. The alternator converts the mechanical energy

of the turbine into electrical energy. The output of the alternator is given to the bus-bars

through transformers, isolators and circuit breakers.

MW : 40.8

Pf : 0.80

MVA : 51

Stator volt : 11kV

Stator current : 2677A

Rotor volt : 246V

Rotor amp : 717A

6.6 Water & Steam Cycle Equipment:

6.6.1 Water & Steam Cycle:

Deaerator HP BFP Feed water control station HP Eco HP drum HP SH

Turbine (HP Steam) Condenser CEP Ejector GSC CPH Deaerator control

valve station Deaerator.

For LP MS another cycle sub-path through LP BFP is maintained:

Deaerator LP BFP LP Eco LP drums LP SH Turbine (LP Injection Steam)

6.6.1.1 Deaerator:

It is in two parts; one is Deaerating column where Deaeration takes place in spray valve cum

tray chamber and another is feed water storage tank which is used as water reservoir tank

with capacity of 27.5 m3.Whole assembly is known as Deaerator. Steam pegging is also done

in Deaerator to increase Deaeration, feed water temp and BFP suction pressure .Condensate

discharge through CPH (condensate preheater comes here in a chamber with 12 spray valve

and 9 tray s and Deaeration takes place. Air comes out of the air vent and water flows down

in reservoir feed water Storage tank.

Deaerator level: Normal : 0 mm

Low (alarm) : (-) 400 mm

Very low (tripping of BFP) : (-) 1500 mm


6.6.1.2 HP BFP:

High pressure Boiler feed pumps are three in nos. and two are continuously running for full

load operation.

HP BFP cooling:

(i) Oil cooling for bearing and oil level around 1/2 of the pot size in maintained in oil pot

(ii) Seal water cooler for cooling DM water, which is used for sealing the gland. The

flushing DM water is further cooled in seal water cooler by ACW water.

(iii) ACW cooling for bearing oil chamber.

Permissive for starting HP BFP:

(i) Suction valve open

(ii) Ready to start -i.e. switchgear remote clearance signal is ok

(iii) Deaerator level ok above

(iv) Pump bearing temp normal -below 80 degree C

(v) Motor bearing temp normal -below 80 degree C

(vi) Motor winding temp normal -below 80 degree C

One recirculation line tapped from discharge line is connected to deaerator to facilitate

minimum discharge flow while BFP is running .The balance leak off line taped from impeller

intermediate stage is also connected to deaerator to balance thrust. The manual valves of

these lines located at deaerator floor should be kept open at the time of starting BFP. Manual

suction valve and motorized discharge valve are located at the floor just above BFP. All the

three discharge valves are opened while starting first BFP on auto.

6.6.1.3 LP BFP:

LP BFPS are similar in constructions and operation as HP BFP mentioned above but with

very low capacity as compared to the HP BFP.

LP BFP cooling:

(i) Oil cooling for bearing and oil level around1/2 of the post size is maintained in oil

pot.

(ii) Seal water cooler for cooling the DM water which is used for sealing the gland .The

flushing DM water is further cooled in seal water cooler by ACW water.

(iii) ACW cooling for bearing oil chamber.

LP BFP tripping;

(i) Discharge pressure : 14kg/cm2

(ii) Deaerator level is very low : (-)1500mm

Permissive for starting LP BFP:


Suction valve open

Ready to start -i.e. switchgear remote clearance signal is ok

Deaerator level not low i.e. above (-) 400 mm

6.6.1.4 Condenser:

Turbine exhaust is connected to condenser. Condenser here used is surface condenser.

Circulating water pump discharge water flows through condenser tubes &cools steam in

surrounding areas coming out of turbine. Hot well is bottom part of condenser where

condensate resulting from condensation of steam is collected and we can add make up water

here to compensate line losses of closed water cycle.

Condenser pressure : (-) 0.9 kg/cm2

Low Howell level : 0 mm (normal)

Condenser cooling water temp. : 33.0 degree C

6.6.1.5 Condenser Extraction Pump:

Condensate Extraction pump ( CEP) are three in nos. and out of them two pumps run for full

load operation .These vertical pumps are used to facilitate pumping the condensate back to

deaerator .

Discharge pressure : 14.8 kg/cm2

Flow : 107 m3/ hr

Full load current : 123 A

Motor rating : 75 Kw

6.6.1.6 Ejector:

Ejectors are used to create vacuum in condenser. Starting ejector is charged initially to create

fast vacuum. Starting Ejector basically consist of a nozzle through which pressure energy of

incoming aux steam is converted in kinetic energy and passing through high velocity it

entails air from condenser and the exhausted air and steam mixture flows to the atmosphere.

Whereas in main ejector aux steam accelerating through nozzle is also being utilized in

heating CEP discharge condensate and the condensed steam flows to condenser through

manual valves instead of being exhausted to atmosphere as in case of starting ejector.

6.6.1.7 Gland Steam Cooler (GSC):

Here condensate flows in GSC tubes and heated gland steam coming out of the turbine gland

sealing.


6.6.1.8 Condensate Preheater (CPH):

CPH is located as a last heat transfer surface in exhaust gas path before flowing to 70m high

stack. Condensate water flowing in CPH tubes heated through exhaust gas.

CPH inlet water temp : 48 degree C

CPH outlet water temp : 94.7 degree C

6.7 HP Bypass & LP Bypass (HPBP& LPBP):

HPBP and LPBP are used to bypass the turbine rolling parameter is achieved. HPBP line is

tapped off from individual HRSG MS line and valves are located at 5 m in front of

condenser. Similarly LPBP line is tapped off from individual HRSG (LP system) and one

valve is located in the front of condenser at 5m and another is behind the condenser at

separate platform. HPBP & LPBP dumps MS directly to condenser after reducing pressure

.Downstream temp are reduced in case of HPBP by spraying BFP discharge water.

HPBP /LPBP control valves flows on following protections:

HPBP /LPBP solenoid valve open on protection.

(i) Generator circuit breaker open

(ii) Turbine tripped

6.8 Auxiliaries:

(i) Circulating Water Pump (CW Pump):

These are three in nos. and located in pump house .These pumps are used for circulating

water through condenser tubes so as to condense the turbine exhaust steam.

Discharge : 2.5kg/cm2

Flow : 4500 m3/HR


Motor rating : 400kW, 6.6kV

(ii) Auxiliary Cooling Water Pump (ACW Pump):

These are two in nos. and also located in pump house. These pumps are used for following

purpose:

(a) BFG bearing and seal water cooling

(b) Generator air cooling

(c) Compressor lubes oil cooling


(d) Turbine bearing oil cooling

(e) In GT area for gas booster compressor and atomizing air cooler ACW pumps along

with CW pumps take suction from pump located underground beneath them and return is

cooled by cooling towers.

Discharge pressure : 4.5 kg/cm2

Flow : 655 m3 /HR


Motor rating : 125 kW, 415v


CHAPTER: 7

CONSTRUCTION DETAIL OF GENERATOR AND EXCITER

Generator:

The generator is two pole, cylindrical rotor, air cooled type-TARI, Siemens, Designs of

BHEL make.

Main components of generator are:

7.1 Stator

7.1.1 Stator frame

7.1.2 Stator core

7.1.3 Stator windings

7.1.4 Stator and covers

7.2 Rotor

7.2.1 Rotor Shaft

7.2.2 Rotor winding and retaining ring

7.2.3 Field connections

7.3 Bearings

7.4 Generator and Air Cooler

7.5 Excitation System

7.1 Stator:

7.1.1 Stator Frame:

Stator frame supports the laminated core and stator winding. It is welded construction

consisting of stator frame housing, two flanged rings, axial and radial ribs. The dimensions

and arrangement of ribs is determined by cooling air passage and required material strength

and stiffness. Ventilating air ducts are provided in the radial ribs. Footings are provided to

support the stator frame on foundation plates by means of bolts.

7.1.2 Stator Core:

Stator core is built from silicon steel electrical grade laminations. Each lamination is made up

from number of individual segments. Segments are stacked on insulating bars which hold

them in position. One bar is kept un- insulated to provide grounding of laminated core.


The laminations are hydraulically compressed and located in frame by means of camping

bolts and pressure plates.

Clamping bolts run through the core and are made of non-magnetic steel and are insulated

from the core to prevent short circuiting of the core. Clamping fingers are provided at the

ends which ensure compression in teeth area. The clamping fingers are made up of non-

magnetic steel to avoid eddy current losses.

7.1.3 Stator Winding:

Stator winding is two layers short pitch winding consisting of stator bars of rectangular cross

section.

Each bar consists of number of separately insulated strands. In slot portion the strands are

transposed to ensure uniform distribution of current over entire cross section of the bar. The

high voltage insulation is epoxy cast resin type bonded with mica. The insulation is

continuous, void free, extremely low moisture absorbent, oil resistant and exhibits excellent

electrical, mechanical and thermal properties. A coat of semi conducting varnish is applied

over the surface of all bars within the sot range to minimize corona discharges between and

slot wall.

All the bars are additionally provided with end corona protection to control the field at that

location and to prevent formation of creep age sparks. Several layers of semi conductive

varnish are applied at varying lengths to ensure uniform electric field. A final wrapping of

glass fabric tape impregnated with epoxy resin is provided which serves as surface protection.

The stator bars are inserted in slots with very small clearances. At the top they are secured by

slot wedges and ripple springs. In the end windings the bars are firmly lasted to supporting

brackets. Spacer blockers are placed between the bars to take care of electromagnetic forces

that may be produced during short-circuits. The beginning and the ends of the three phase

winding are solidly bolted to output leads with flexible. Output leads are copper flats inserted

into insulating sleeve.

7.1.4 Stator End Covers:

Stator and covers are attached to the end flanges of stator frame and rest on a foundation

frame. The end covers aluminum alloy castings.


Fig No.7.1-Steam Turbine

Fig No.7.2- Bearing


Fig No.7.3- Steam Turbine Cover

7.2 Rotor:

7.2.1 Rotor Shaft:

The rotor shaft is single piece solid forging. Slots for winding are milled into rotor body.

Axial and radial holes are provided at the base of the rotor teeth forming air cooling ducts.

7.2.2 Rotor Winding:

The rotor winding consists of several series connected coils which form north and south

poles. The conductors have rectangular cross section and are provided with axial slots for

radial discharge of hot air. Individual conductor is bending to obtain half turn. After insertion

into slots these turns are brazed to form one full turn. Individual coils are series connected so

that one north and one South Pole are obtained. Conductors are made of copper having 0.1%

silver content to provide high strength at higher temperatures so that coil deformation due to

thermal stresses is avoided. Individual turn of the coil is insulated with glass fiber tape. Glass

fiber laminates are used slot insulation.

To protect the winding against the effects of centrifugal forces the winding is secured in the

slots with wedges. Slot wedges are made from alloy high strength and high electrical

conductivity material. This also acts as damper winding. At the ends, slot wedges are short

circuited through the retaining ring which acts as short circuiting ring to induced currents in

damper windings. Retaining rings of high strength of non-magnet steel are provided.


7.2.3 Field Connections:

The connections of the rotor windings are brought out at the exciter side shaft end through

rotor shaft bore.

7.3 Bearings:

The rotor is supported in two sleeve bearings. To eliminate shaft currents the exciter end

bearing is insulated from the foundation frame & oil piping. Temperatures of the bearing are

monitored by two RTDs embedded in the lower half of the sleeve bearing. Bearings also have

provision of fixing vibration pickups to monitor bearing vibrations transmitted from the shaft.

COMPONENTS RATINGS

HEADER PRESSURE ( kg/cm2 ) 8.8 kg/cm2

LUBE OIL TANK TEMPERATURE (degree C ) 50 degree C

AUXILARY STEAM PRESSURE 11.2 kg/cm2

AUXILARY STEAM TEMPERATURE (degree C ) 180 degree C

CONDENSOR VACCUME VALUE ( kg/cm2 ) -0.92 kg/cm2

SEAL STEAM PRESSURE ( kg/cm2 ) 0.3 kg/cm2

SEAL STEAM TEMPERATURE (degree C ) 120 degree C

CEP HEADER PRESSURE ( kg/cm2 ) 15 kg

CEP MOTOR CURRENT ( amp ) 95 amp

HPCV POSITION 0-100%

LPCV POSITION 0-100%

CONTROL OIL PRESSURE ( kg/cm2 ) 8 kg/cm2

TRIP OIL PRESSURE ( kg/cm2 ) 9 kg/cm2

BEARING OIL PRESSURE ( kg/cm2 ) 0.35 kg/cm2

BEARING OIL TEMPERATURE (degree C ) 55 degree C

STEAM TURBINE (rpm) 3000 rpm

GENERATOR (rpm) 3000 rpm

GENERATING VOLTAGE ( kilo volt ) 11kv

TURBINE MW 37.5 MW


TYPE OF COOLING ONAN/ONAF

RATING H.V (M.V.A) 40/50

RATING L.V (M.V.A) 40/50

NO LOAD VOLTAGE H.V (KV) 138

NO LOAD VOLTAGE L.V (KV) 11

LINE CURRENT H.V (AMPS.) 167.35 209.19

2099.4 2624.32

LINE CURRENT L.V (AMPS.)

TEMPERATURE RISE OIL (DEGREE C) 50 degree C

TEMPERATURE RISE WINDING (DEGREE C) 55 degree C

PHASE 3

FREQUENCY (Hz) 50

CONNECTON SYMBOL 11

MANUFACTURING UNIT JHANSI

% GURANTED IMPEDENCE AT NORMAL TAP

VOLTAGE % (HV-LV)

12.5 + ISTOL (AT 50 MVA

BASED )

CORE AND WINDING (Kg) 35000

WEIGHT OF OIL (Kg) (INCLUDING 10%

EXTRA)

21500

TOTAL WEIGHT INCLUDING OIL (Kg) 87000

CONNECTON SYMBOL 11

TEMPERATURE RISE OIL (DEGREE C) 50 degree C

OIL QUANTITY (LITRE) (INCLUDING 10%

EXTRA )

24000

TRANSPORT WEIGHT (Kg) (GAS FILLED) 45000

UNTANKING WEIGHT (Kg) 35000

Table No. 7.1: Steam Turbine Generator


VOLTAGE LEVEL INSULATION

H.V 650 KVP/300 K.V.

L.V 75 KVP/28 K.V.

H.V.N 95 KVP/38 K.V.

Table No. 7.2: Insulation Level

7.4 Air Cooling Circuits:

The cooling air is circulated in the generator by two axial flow fans fixed at each end of the

rotor shaft. Cold air is drawn by fans from cooler compartment located at the side of the

generator.

The cooling air directed into the rotor end winding and cools the windings. Some air flows in

the rotor slots at bottom duct from where it is discharged into the air gap via radial ventilating

slots in the coil and bores in the rotor wedges.

Part of the flow is directed over the stator overhang to the cold air duct and to the gap

between the stator frame and stator core. Air then flows through ventilating ducts in the core

into the air gap.

The balanced air is directed into the air gap over the retaining rings cooling it.

7.5 Excitation System:

The excitation system is of brushless type and consists of following-

1. Three phase pilot exciter

2. Three phase main exciter

3. Rectified wheel

The three phase pilot exciter is a permanent magnet type. Three phase output from the pilot

exciter is fed into the AVR (Automatic Voltage Regulator).From the AVR regulated dc

output is fed to the stationary field coils of main exciter. The three phase output from the

rotating armature of the main exciter is fed to the rectifier wheel, from where it is fed to the

field winding of the generator rotor through dc leads in the rotor shaft.

7.5.1 Pilot Exciter:

Pilot exciter is six pole units. The stator is consists of laminated core and carries three phase

winding. Rotor consists of hub on which six permanent magnets poles are mounted.


7.5.2 Main Exciter:

Main exciter is six pole revolving armature types. Field winding and poles are mounted on

stator. At the pole shoe the damper winding is provided. Between the two poles a quadrature

axis coil is fitted for induced measurement of armature current or generator rotor current.

7.5.3 Rectifier Wheel:

Main components of the rectifier wheels are silicon diodes arranged in three phase bridge

configuration. Each diode is fixed in a heat sink. A fuse provided for each diode to switch off

the diode when it fails. These fuses in the diodes can be checked while generator is running,

with the help of stroboscope.


CHAPTER: 8

132 KV SWITCH YARD

Ramgarh GTPP contains 132 KV switch Yard. The switchyard houses transformers, circuit

breakers, and switches for connecting and disconnecting the transformers and circuit

breakers. It also has lightning arrestors for the protection of power station against lightning

strokes.

The supply to the bus bars from alternators is taken through the transformers and circuit

breakers of suitable ratings.

Some components are:

8.1 Bus Bars:

Bus Bars term is used for a main bar or conductor carrying an electric current to which many

connections may be made.

There are two buses of 132 KV, 800A, in Ramgarh GTPP to which incoming and outgoing

feeders, Bus Couplers, Isolators, Circuit Breakers, protective Relays, Current Transformers

(CT) and Potential Transformers (PT) are connected are connected.

One Bus is usually is called ‘main’ bus and the other ‘auxiliary’ or ‘transfer’ bus.

The switches used for connecting feeders or equipment to one bus or the other are called

selector or transfer switches.

8.2 Insulators:

The porcelain insulators employed in switch yard of the post and bushing type. They serve as

supports and insulation of the bus bars.

Types of insulators:

These are the common classes of insulator:

Pin type insulator - As the name suggests, the pin type insulator is mounted on a pin on the

cross-arm on the pole. There is a groove on the upper end of the insulator. The conductor

passes through this groove and is tied to the insulator with annealed wire of the same material

as the conductor. Pin type insulators are used for transmission and distribution of

communications, and electric power at voltages up to 33 kV. Insulators made for operating

voltages between 33kV and 69kV tend to be very bulky.


Post insulator - A type of insulator in the 1930s that is more compact than traditional pin-

type insulators and which has rapidly replaced many pin-type insulators on lines up to 69kV

and in some configurations, can be made for operation at up to 115kV.

Suspension insulator - For voltages greater than 33 kV, it is a usual practice to use

suspension type insulators, consisting of a number of glass or porcelain discs connected in

series by metal links in the form of a string. The conductor is suspended at the bottom end of

this string while the top end is secured to the cross-arm of the tower. The number of disc

units used depends on the voltage.


Strain insulator - A dead end or anchor pole or tower is used where a straight section of line

ends, or angles off in another direction. These poles must withstand the lateral (horizontal)

tension of the long straight section of wire. In order to support this lateral load, strain

insulators are used. For low voltage lines (less than 11 kV), shackle insulators are used as

strain insulators. However, for high voltage transmission lines, strings of cap-and-pin

(suspension) insulators are used, attached to the cross arm in a horizontal direction. When the

tension load in lines is exceedingly high, such as at long river spans, two or more strings are

used in parallel.

Shackle insulator - In early days, the shackle insulators were used as strain insulators. But

now a day, they are frequently used for low voltage distribution lines. Such insulators can be

used either in a horizontal position or in a vertical position. They can be directly fixed to the

pole with a bolt or to the cross arm.

8.3 Isolators:

Isolator is off load switch. Isolators are not equipped with arc quenching devices and

therefore, not used to open circuits carrying current. Isolator isolates one portion of the circuit

from another and is not intended to be opened while current is flowing. Isolators must not be

opened until the circuit is interrupted by some other means. If an isolator is opened

carelessly, when a heavy current, the resulting arc could easily cause a flash over to earth.


This may shatter the supporting insulators and may even cause the fatal accident to the

operator, particularly in high voltage circuits.

While closing a circuit, the isolator is closed first, then circuit breaker. Isolators are necessary

on supply side of circuit breakers in order to ensure isolation (disconnection) of the circuit

breaker from the live parts for the purpose of maintenance.

8.4 Circuit Breakers:

A circuit breaker is an on load switch. A circuit breaker is a mechanical device designed to

open or close contact members, thus closing or opening an electrical circuit under normal or

abnormal conditions. It is so designed that it can be operated manually (or by remote control)

under normal conditions and automatically under fault conditions. An automatic circuit

breaker is equipped with a trip coil connected to a relay or other means, designed to open or

break automatically under abnormal conditions, such as over current.

SF6 circuit breakers are used in RGTPP.

A circuit breaker must carry normal load currents without over heating or damage and must

quickly open short-circuit currents without serious damage to itself and with a minimum

burning contacts. Circuit breakers are rated in maximum voltage, maximum continuous

current carrying capability, and maximum interrupting capability, maximum momentary and

4-second current carrying capability.

Thus functions of the circuit breaker are-

1. To carry fill load current continuously

2. To open and close the circuit on no load

3. To make and break the normal operating current

4. To make and break the short circuit currents of magnitude up to which it is designed for.

8.5 Protective Relays:

The protective relay is an electrical device interposed between the main circuit and the circuit

breaker in such a manner that any abnormality in the current acts on the relay, which in turn,

if the

Abnormality is of dangerous character, causes the breaker to open and so to isolate the faulty

element. The protective relay ensures the safety of the circuit equipment from any damage,

which might otherwise cause by fault.

All the relays have three essential fundamental elements:


1. Sensing Element sometimes also called the measuring elements, responds to the change

actuating quantity, the current in a protected system in case of over current relay.

2. Comparing Element serves to compare the action of the actuating quantity on the relay

with a pre-selected relay setting.

3. Control Element, on a pickup of the relay, accomplishes a sudden change in the control

quantity such as closing of the operative current circuit.

The connections are divided into three main circuits consisting of:

Primary winding of the CT connected in series with the main circuit to be protected.

Secondary winding of the CT and the relay operating winding and

The tripping circuit

Under normal operating conditions, the voltage induced in the secondary winding of the CT

is small and, therefore, current flowing in the relay-operating coil is insufficient in magnitude

to close the relay contacts. This keeps the trip coil of the circuit breaker de-energized.

Consequently, the circuit breaker contacts remain closed and it carries the normal load

current. When a fault occurs, a large current flows through the primary of the CT. this

increases the voltage induced in the secondary and hence the

Current flowing through the relay operating coil the relay contacts are closed and the trip coil

of the breaker gets energized to open the breaker contacts.

8.6 Current Transformers (CT):

A current transformer basically consists of an iron core on which are wound a primary and

one or two secondary windings. The primary is inserted in the power circuit (the circuit in

which the current is to be measured) and the secondary winding of the current transformer is

connected to the indicating and metering equipment and relays are connected.

At GTPP, current transformers are provided in switchyard to measure the current of the

feeders. There are five cores in current transformers. The 1st, 2nd, 4th and 5th cores are

provided for protection and the third core is used for measurement purpose.

These CT are of the ratio of 200/1, 400/1, and 1200/1. When the rated current of CT flows

through its primary winding, according to transformation ratio the current in the secondary of

the CT will flow and will be measured by the indicating instruments connected to the

secondary of the CT.


8.7 Potential Transformers (PT)/ Voltage Transformer (VT):

At GTPP, in switchyard, there are two voltage transformers, namely VT-1 and VT-2, to

measure the voltage on the bus bars. The primary winding of the VT is connected to the main

bus bar of the switchgear installation and, various indicating and metering equipment and

relays are connected to the secondary winding. When the rated high voltage is applied to the

primary of the voltage transformer, the voltage of some specific value will appear on the

secondary of the VT, and the indicating equipment measure this.

8.8 Lightning Arrestors:

A lightning arrester is basically a surge diverter and used for the protection of power system

against the high voltage surges. It is connected between the line and earth so as to divert the

incoming extra high voltage wave to the earth.

It consists of a linear resistance. At GTPP, it is so designed that at 132 KV its resistance

remains infinity and during lightning, when the excess incoming voltage (near about 1 crore

or 10 crore) falls on the line, this resistance, falls down to zero value and it shorts the circuit,

resulting in flow of lightning current to earth.

8.9 Current Voltage Transformers (CVT):

CVT are provided for synchronization purpose at feeders to measure phase angle, voltage and

frequency. For joining the feeders coming from different places or for synchronization of

feeder’s voltage, phase angle and frequency at the joining place must be of same value.

8.10 Wave Trap:

All the telephone lines in RGTPP are connected through Wave Trap to ensure effective

communication in emergencies.

8.11 Bus Coupler:

Bus coupler is connected to couple two buses, which are provided in parallel. When fault

occurs in one bus, load of the faulted bus is transferred to the second bus.


CONCLUSION

After training in the RGTPP 270 MW combined cycle power plant, we can describe that this

power plant is a very efficient one as compared to other power plants in its series.

Also, we would like to add up that it is very compact in size, less palliative to nature, easily

controlled & decent power plant that we had ever seen.

We really got a treasure of practical knowledge from the RGTPP employees. In future we are

sure that this Practical training in RGTPP is going to help us in our rest of the studies


DO’S AND DON’TS

1. Smoking is not allowed

2. Before starting of any job, make certain you have obtain the necessary work permit.

3. Whenever any dangerous conditions is noted. It should be reported immediately to

the action supervisor and fire safety action.

4. Unnecessary running is not allowed.

5. In protective measures employees must not walk through of across any operating

unit unless there duties require them to do so.

6. Where walkwise are provided use them instead of shortcuts.

7. All stairways platforms and walkways must be kept clear of any obstructions at

all times.

8. After a completion of the work, all left over junk and tools are to be removing to

the proper place.

9. All condition that may affect the safety of the employees or equipment must

be reported at once.

10. Walking on the pipeline is prohibited.


SAFETY PRECAUTIONS

Safety is one of the fundamental needs of all living beings. Accident is an unwanted

event and held due to carelessness. So necessary precautions should be taken to avoid such

accidents. In order to get the best out of an individual his physical safety is essential. The

following are two main reasons, which include the accidents:

1. Unwanted Acts

2. Unwanted conditions

In an accident occurred by the unwanted acts, the workers are directly responsible.

These types of accidents are held by improper acts, carelessness, shortcuts for

completing work early by keeping awareness, patience in doing work. The main reasons

which motivate the accidents in the form of unwanted acts are as follows:-

1. Use of machine or equipment without permission.

2. Filling and loading the materials improperly.

3. Keeping high speed of

machine.

4. Maintaining, oiling and greasing the machine in running Conditions.

5. Standing in unsafe conditions.

6. Use of unsafe tool and safety equipment.

7. Lifting and keeping the material unsafe.

SAFETY RULES

There are many safety rules for safety but main golden rules are as

follows:

1. Comply with all safety rules and regulations.

2. Correct or report unsafe conditions immediately to supervisor.

3. Wear rotating safety equipment only when authority is given.

4. Use right tool for the right job and use it safely.

5. Keep the workplace clean and tidy.


REFERENCE

Manuals provided by the ramgarh gas and thermal power plant.

Books collected:

Power System by J.B. Gupta

Electrical machines by Aashfaq Husain

Mechanical equipment by C. Richardson

Websites

www.ntpc.co.in

www.electrical4u.com

report on rgtpp jaisalmer

Engineering