TRAINING REPORT ON

NATIONAL CAPITAL POWER STATION

DADRI

CONTENTS ABOUT NTPC INTRODUCTION TO GAS POWER STATION COMBINED CYCLE HOW DOES A COMBINED-CYCLE POWER PLANTWORK? GAS TURBINE STARTING SYSTEM STEAM TURBINE TRANSMISSION OF GENERATED POWER ONTO THE THE

GRID TRANSFORMERS SWITCHYARD CONDESOR AND COOLING TOWER NATURAL GAS CONTROL ROOM

ABOUT NTPC NTPC ,the largest power company in india ,was setup in 1975 to accelerate power

development in country. NTPC Dadri is a unique power plant of NTPC group which has coal based thermal

plant and gas based thermal plant of 1820 MW ,817 MW and solar based plant 5MW respectively.

NTPC has installed capacity of 29,397MW. It has 15 coal based power station ,7 gas based power stations and 1 solarbased

power station. It plans to be 75,000MW company by 2017.

INTRODUCTION TO GAS POWER STATION

The gas turbine has found increasing application due to the following potential advantages over competive equipment.

• Small size and weight per horsepower • Rapid loading capability • Self-contained packaged unit • Moderate first cost • No cooling water required • Easy maintenance • High reliability • Waste heat available for combined cycle application. • Low Gestation Period • Low Pollution Hazard

COMBINED CYCLE Combined Cycle Power Plants

GT1 GT2 GT3 GT4

ST1 ST2MODULE 1 MODULE 2

Combined Cycle Power Plants integrates two power conversion cycles namely.

1.Brayton Cycle(Gas Turbines)

2.RankinCycle(Conventional steam power plant)

with the principal objective of increasing overall plant efficiency

Brayton Cycle

Gas Turbine plant-operate on Brayton Cycle in which air iscompressed this compressed air is heated in the combustor by burning fuel combustion produced is allowed to expand In theTurbine and the turbine is coupled with the generator

RANKINE CYCLE The conversion of heat energy to mechanical energy with the aid of steam is carried

out through this cycle The initial state of the working fluid is water (point-3) which, at a certain temperature

is compressed by a pump (process 3-4) and fed to the boiler. In the boiler the compressed water is heated at constant pressure (process 4-5-6-1). Modern steam power plants have steam temperature in the range of 500C to 550C at

the inlet of the turbine

HOW DOES A COMBINED CYCLE POWER PLANT WORKPOWER GENERATION: Air Inlet The amount of air needed for combustion is800,000 cubic feet per

minute. This air is drawn though the large air inlet section where it is cleaned,

cooled and controlled, in order to reduce noise.

Turbine-Generators The air then enters the gas turbine where it is compressed, mixed with

natural gas and ignited , which causes it to expand. The pressure created from the expansion spins the turbine blades , which are attached to a shaft and a generator , creating electricity.

Each gas turbine produces 185 megawatts (MW)of electricity.

GAS TURBINE STARTING SYSTEM

A typical hydraulic starting system for each gas turbine is consist of:

Starting motor, electric AC induction motor Hydraulic torque converter Auxiliary Gear Couplings The electric starting motor drives the hydraulic torque generator

through a coupling.

The static frequency converter serves the same

function of starting, accelerating running at preset speed by starting the generator as a synchronous motor by feeding variable frequency current drawn from the connected grid.

GAS TURBINE

Steam Turbine

The steam turbine is capable of producing upto 240 MW. It is located on top of the condenser, across from the cooling tower.

Steam enters the turbine with temperatures as high as 1200 degrees Cand pressure as strong as 2,200 pounds per square inch. The pressure of the steam is used to spin turbine blades that are attached to a rotor and a generator, producing additional electricity, about100 megawatts per HRSG unit.

After the steam is spent in the turbine process , the residual steam leaves the turbine at low pressure and low heat, about 100 degrees. This exhaust steam passes into a condenser, to be turned back into water.

By using this “combined-cycle” process, two gasturbines and one steam turbine, we can producea total of about 600 megawatts of electricity

.

Transmission of Generated Power Onto the Grid Transformers

Transmission of Generated Power Onto the Grid Transformers

The transformers take the generated 13,000 volts and “transform” them to 230,000 volts, which is the required voltage needed for transmission to the nearby tower that sends power to the substation.

A small amount of generation is directed to “Auxiliary transformers” which “transform” the generated voltage to a lower voltage, so it may be used by the plant to power our own pumps, fans, and motors. The Metcalf Energy Center requires 12 – 15 megawatts to operate

.Switchyard From each transformer, the power passes underground into our

switchyard. The power from all of the generators comes together there , where it is measured, metered and directed on to the grid.

The proximity of the site to a large, existing PG&T substation makes it a good place to build a power plant and the nearest transmission tower is only about 200 feet away.

Condenser and Cooling Tower

The purpose of the condenser is to turn low energy steam back into pure water for use in the Heat Recovery Steam Generator.

The purpose of the cooling tower is to cool the circulating water that passes through the condenser. It consists of ten cells with large fan son top, inside the cone-like stacks, and a basin of water underneath.

.

Natural Gas Natural gas fuels the combustion turbines. Each turbine can consume up to

2,000 MMBTU per hour The pipeline was built 60 feet underground and passed under highways,

creek, train tracks, and environmentally sensitive areas. The pipeline enters the site just behind the water tanks, where equipment

regulates and measures the natural gas composition, flow and pressure.

Control Room From the control room, the plant operators monitor and operate the facility, via

the plant’s “ Distributed Control System”, with the click of a mouse, viewing graphic representations of all MEC systems on various screens.

The system gives operators both audible and visual signals to keep them informed of plant conditions at all times and to determine when preventative maintenance is required