June 2011

Jyothish Kumar C G Jostin John Fedreral Institute Of Science & Technology,Angamaly,Kerala

Summer Training Report- NTPC, Kayamkulam

ACKNOWLEDGEMENT

We thank Mrs. Sreekumari Radhakrishnan for allowing us to

undergo summer training at NTPC Kayamkulam and all of the HR

team of the Institute for their continued guidance. We also wish to

convey our warm regards to Mr. Manu George Thomas,

Mr.Ashil Thomas & Mr. Dinesh K V for providing us with all the

knowledge database that we needed for this report.

We also thank Mr. M G K Pillai for providing us this wonderful

opportunity to work with the NTPC family.

Overview of NTPC

NTPC was set up in the central sector in the 1975 in

response to widening demand & supply gap with the main

objective of planning, promoting & organizing an integrated

development to thermal power in India. Ever since its

inception, NTPC has never looked back and the corporation

is treading steps of success one after the other.Today NTPC

contributes more than 1/ 4th of the total power generation in

India.

NTPC KAYAMKULAM

BRIEF DISCRIPTION

• Established in : 1998

• Project Name : Rajiv Gandhi Combined Cycle Power Project

(RGCCPP)

• Type of station : Gas based combined cycle

• Approved Invetment : Rs. 1189.94 crore

• Location : Choolatheruvu in Alappuzha district of Kerala

• Fuel : Naphtha

• Fuel source : BPCL

• Water source : Achankovil river

• Gas Turbine Output : 2 X 115 MW

• Steam Turbine Output : 1 X 120 MW

• Net plant Output : 350 MW

• Beneficiary States : Kerala & Tamil Nadu (with consent of Kerala)

Introduction To Gas Power Plants

The development of the sector in the country, since independence has been predominantly through the State Electricity Boards. In order to supplement the effects of the states in accelerating power development and to promote power development on a regional basis to enable the optimum utilisation of energy resources, the Government of India decided to take up a programme of establishment of large hydro and thermal power stations in the central sector on a regional basis. With this in view, the Government set up the National Thermal Power Corporation Ltd., in November 1975 with the objective of planning, construction, commissioning, operation and maintenance of Super Thermal and Gas Based Power projects in the country.

The power plant consists of gas turbine generating units waste heat recovery boilers, steam turbo generator, auxilliary electrical and mechanical equipments. The power generated at this power station is fed over 220 KV AC transmission system and is distributed to substations at Kundara and Pallam.

The function of a gas turbine in a combined cycle power plant is to drive a generator which produce electricity and to provide input heat for the steam cycle. Power for driving the compressor

is also derived from gas turbine.

Combined Cycle to improve efficiency

Combined Cycle power plant integrates two power conversion cycles namely. Brayton Cycle (Gas Turbines) and Rankin Cycle (Conventional steam power plant) with the principal objective of increasing overall plant efficiency.

In the above two cycles gas turbine exhaust is at a temperature of 500–550 0C and in Rankine Cycle heat is required to generate steam at the temperature of 500-550 0C. so, why not use the gas-turbine exhaust to generate steam in the Rankine cycle and save the fuel required to heat the water ? Combined Cycle does just the same.

The efficiency of Gas Turbine cycle alone is 30% and the efficiency of Rankine Cycle is 35%. The overall efficiency of combined cycle comes to 48%.

Black Start System To start a gas turbine in the event of AC-power failure an emergency black start system is provided. It also helps in safe closing down of the gas turbine and its auxiliaries following a ‘trip’ in the event of grid collapse. The black start system consists of a separate diesel engine or a gas turbine driven synchronous generator connected to station switch gear bus. It

can be operated manually from local or remote and also it automatically comes into operation following a black out condition. Capacity of the black start unit should be such that it can supply the total auxiliary power required to start a gas turbine from standstill condition.RGCCPP is provided with diesel generator set for the duty.

How Does A Combined-Cycle Power Plant Work?

Air Inlet

The amount of air needed for combustion 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 fuel Naptha 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 115 megawatts (MW) of

electricity.

Heat Recovery Steam Generator

(HRSG)

The hot ehaust gas exits the turbine at about 550 degree

Celsius and then passes through the Heat Recovery Steam

Generator (HRSG).

In the HRSG, there are tubes filled with demineralised

water. The hot exhaust gas coming from the turbines passes

through these tubes, which act like a radiator, boiling the

water inside the tubes, and turning that water into steam.

The gas then exits the power plant through the exhaust

stack at a much cooler 100 degree Celsius, after having

given up most of its heat to the steam process.

This steam is fed to the steam turbine through large pipes.

Steam Turbine

The steam turbine is capable of producing up to 120 MW.

It is located on top of the condenser, across from the

cooling tower.

Steam enters the turbine with temperatures as high as 550

degree Celsius and pressure as strong as 2,200 pounds per

square inch. The pressure of the steam is used to spin

turbine blades which is coupled to a generator, producing

additional electricity, about 120 MW 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 degree Celsius. This exhaust steam passes into a

condenser, to be turned back into water.

By using this “combined-cycle” process, two gas turbines

and one steam turbine, we can produce a total of about 350

MW of electricity.

Transmission of Generated Power

Onto the Grid

The Gas Turbine and Steam Turbine generators produce

power at 10.5 kV.

The transformers take the generated 10.5 kV and

“transform” them to 220 kV, 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

6.6 kV, so that it may be used by the plant to power its own

pumps, fans, and motors.

Gas Insulated Switchyard(GIS)

The most salient feature of NTPC Kayamkulam is the GIS,

which is the 1st of its kind in India.

GIS is extremely compact compared to other conventional

switchyards.

Unlike conventional switchyards here the insulation

between three phase lines(R,Y,B) in each busbar is

provided by SF6 which is a highly inert gas.

From each transformer, the power passes underground into

the switchyard.The power from all of the generators comes

together there, where it is measured, metered and directed

onto the grid.

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 8

cells with large fans on top, inside the cone-like stacks, and

a basin of water underneath.

The cool basin water absorbs all of the heat from the

residual steam after being exhausted from the steam

turbine and it is then piped back to the top of the cooling

tower.

As the cool water drops into the basin, hot wet air goes

out of the stacks. Normally, hot moist air mixes with cooler

dry air, and typically a water vapor plume can be formed.

DeMineralising Plant

By gravity pipe

Reservoir

River Achankovil

Muttam makeup-water Pump House

Raw-water Pump House

Stilling chamberChlorine + lime

ClarifierCoagulated alum & PAC

Clarified water storage tank

Pure water

Domestic purpose , DM-Plant

Cooling tower makeup pump

Gravity sand, filter-bed

Potable water to colony, plant and DM-feeder

Filtered water storage tank

DeMineralising Plant

It is the plant where the purified water to condenser is demineralised. Demineralisation is done to prevent the rusting of condensing chamber and its pipes. It has the following five stages:

Actuated Carbon Filter (ACF) Strong Acid-Cation exchange bed (SAC) Degasser tower Strong Base Anion exchange bed Mixed Bed Unit (MBU)

Passing through these five stages, purified water is demineralised and fed to the condenser.

CONCLUSION

In today’s society electricity is a prerequisite. Being electrical engineering students, studying about its generation has been our necessity.

The past six days in NTPC gave us an opportunity to explore the dimensions of power generation, with the proper guidance of the qualified and skilled employees of NTPC.

The knowledge we gained from this training would be highly beneficial in our further studies and career.