NTPC

A Practical Training Seminaron

“Switchyard”

from

“NTPC Kahalgaon”

Presented By:Sunny Kr-IVII Sem Electrical

National Thermal PowerCorporation Ltd.

NTPC Kahalgaon

Contents (24,verdana,justified)

3X500MW (Stage-II) Made By BHEL

CORPORATE VISION

“A world class integrated power major, powering India's growth with increasing global presence.”

Vision A world class integrated power major, powering

India's growth with increasing global presence

About NTPC

All stations of NTPC are ISO 14001 certified NTPC is the second largest owner of trees in

the country after the Forest department NTPC was set up in 1975 with 100% ownership

by the Government of India. In the last 30 years, NTPC has grown into the largest power utility in India

In 1997, Government of India granted NTPC status of “Navratna” being one of the nine jewels of India, enhancing the powers to the Board of Directors

About NTPC

NTPC has also set up a plan to achieve a target of 50,000MW generation capacity

NTPC has embarked on plans to become a 132 GW company by 2032

NTPC is the largest power utility in India, accounting for about 20% Of India’s installed capacity.

The name of the Company "National Thermal Power Corporation Limited" has been changed to"NTPC Limited" with effect from October 28, 2005.

KhSTPP At a Glance

Project name: Kahalgaon Super Thermal Power Project (KhSTPP)

No of units X Capacity : 4X210 MW (Stage-I) 3X500 MW (Stage-II)

Total Capacity: 2340MW

Project setting up by : National Thermal Power Corporation Ltd.(NTPC)

Switchyard Contents

• 400 & 132KV Switchyard• Current Transformer• Capacitive Voltage Transformer• Circuit Breaker• Isolator• Line Trap & Wave Trap• Bus Reactor• Bus Post Insulator• Inter Connecting Transformer

Switchyard

Switchyard

• Plays a very important role as a junction between the generation and transmission which carries the generated power to its destination

• It is a yard or an open area in which different kinds of instruments are located

• Plays very vital role in the Power Plant. It may be describe as the heart of the plant.

• Responsible for connecting and disconnectiong the transmission lines as per requirement

Switchyard

The power generated by Turbo generators of units1 to 4 is 15.75 KV and units 5 to 7 is 21 KVWhich is stepped up to 400 KV by the GeneratingTransformer and then transmitted to switchyard. In KhSTPP there are two switchyard sections:• 400 KV• 132 KVSwitchyard is of conventional air insulated type

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Slide no.1

400 & 132KV Switchyard At Glance

Power transmission is done at a higher voltageWhich • reduces transmission losses • facilitiate higher utilisation of generation

capacity

400 & 132KV Switchyard At Glance

There are total 43 bays in 400KV Switchyard. ABay is basically a way for the incoming powerfrom generator as well as outgoing power fordistribution. There are 2 Main buses in 400 KV switchyard Main Bus 1 & 2.

Current Transformer

C.T. is used for two major functions:• Metering which means current measurement• Protection such as over current protection,

Overload,Earth fault protection ,Bus bar protection, Bus differential protection

C.T. is designed in such a way so that its corematerial would give high accuracy with lowsaturation factor . Core material is made up of CRGO silicon steel

Current Transformer

Capacitive Voltage Transformer

• Steps down higher voltage to a lower value that can be measured using the measuring instrument

• Connected between phase and ground in parallel to the circuit.

• It blocks power frequency of 50 Hz & allows flow of carrier frequency for communication

• Simultaneously the CVTs are used as coupling capacitors for Power Line Carrier Communication (PLCC).

Capacitive Voltage TransformerThe device has 4 terminals• High voltage terminal• Ground terminal• 2 secondary terminals

which connect to instrumentation or protectiverelayCVT secondary voltage, v=k*V*C1/(C1+C2)V= primary voltagek= secondary transformation ratio

Capacitive Voltage Transformer

Circuit Breaker

A circuit breaker is a switching i.e. currentinterrupting or making device• Makes or breaks a circuit either manually or by

remote control under normal conditions• Breaks a circuit automatically under fault

conditions• Makes a circuit either manually or by remote

control under fault conditions

Circuit Breaker

Operating mechanism• A circuit breaker essentially consists of fixed

and moving contacts which remain closed under the normal operating conditions

• During fault, the trip coils of the circuit breaker get energized and the moving contacts are pulled apart by some mechanism, thus opening the circuit.

• An arc is struck between them. The current is thus able to continue until the discharge ceases.

Circuit Breaker

Double Breaker Scheme

Tripping Circuit

Circuit Breaker

Types:• SF6 Circuit Breaker• Air Blast CircuitBreaker• Vacuum Circuit Breaker• Oil Circuit Breaker

SF6 CB at KhSTPP

Advantages of SF6 CB• Inert gas with high dielectric strength.• Colorless and odourless.• Non-toxic and non- inflammable.• It has low maintenance cost, light foundation

requirements and minimum auxilliary equipments.

• Gas pressure in the chamber is at 7.5 bar• There are no carbon deposits so that tracking

and insulation problems are eliminated. • The decomposition products of arcing are not

explosive hence no chance of fire.

Isolator

Isolator is a manual switch used for disconnecting the network sections on no load.

Always used in OFF-LOAD condition

It provides:-• Physical Separation of live contacts &• Maintain high di-electric strength across open

contacts.

Isolator at KhSTPP

Line trap

• Trap higher carrier frequency of 20 hz to 20 khz and above and allow the flow of power frequency (50 Hz). High frequencies also get generated due to high capacitance to earth in long transmission lines.

• Offers high impedance to carrier frequency where as very low impedance to power frequency.

Line trap

Line trap is a parallelLC circuit

Line Trap= High Impedance for PLC signal

Low Impedance for Power energy

Wave Trap

• To prevent high frequency signals from entering other zones.• Wave Trap is used for

protection of the transmission line and communication between substations.• Sends inter-trip signal to the

other end CB so that the fault can be isolated at the earliest time.

Lightning Arrestor

A station lightning arrestor is ofsingle-phase design, suitable foroutdoor service.It is designed to limit surge voltagesto a safe value by discharging the surge current to ground.

Bus Reactor

Purpose :• Whenever there is increase in system voltage

due to capacitance formation, it injects inductive power to the system & neutralizes it

• Also limits fault current

Bus Post InsulatorThese provide necessaryinsulation between lineconductors and supports andthus prevent leakage of currentfrom conductors to earth.

Inter Connecting Transformer• The function of the inter-connecting transformer is

as the name suggests - to inter-connect two systems at different voltages.

• Normally, they will be either 400kV/132kV or 220kV/110kV, of say about 100 MVA rating.

• They are bi-directional. During the plant start-up, they "import" power from the grid either at 400kV or 220kV and step down to 132kV or 110kV to supply the station auxiliaries.

• Once the plant is started and synchronized to the grid, the same transformer can now be used to "export" power to the grid.

Topic Name

Contents (24,verdana,justified)

Slide no.1

Thank You…