MAJOR ELECTRICAL EQUIPMENT IN POWER PLANTS

Submitted To:- Er. Sonika Singh

Presented By :- Gurdit Singh1184238EE 2k10

Power plant consists of Variety of electrical equipment

Major electrical equipment are Alternator,

Exciters, Synchronizing Equipment, Circuit Breakers, current and potential transformers, relays and protection equipment, isolator, lighting arresters, earthing equipment, station transformer, battery and motor for driving auxiliaries

Introduction

In electricity generation, an electric generator is a device that converts mechanical energy to electrical energy. A generator forces electric current to flow through an external circuit. 

Generator are varies in type according to the type power plant

Generator decide the size of power plant

Generators

Turbo generator for thermal power station

Excitation system is required to provide the necessary field current to the rotor winding of a synchronous machine. Availability of excitation at all times important. Larger the load currents, lower the speed and lagging power factor which require more excitation.

Types 1. DC Excitation System 2. AC Excitation

System 3. Static Excitation System

Exciters

Power transformer are used for stepping-up the voltage for transmission at generating stations and for stepping-down voltage for distribution purpose.

Normally naturally cooled, oil immersed, two winding, three phase transformers are used up to the rating of 10 MVA.

For regulating the voltage , transformers are provide with on load tap changers

They are put in operation during large load hours and disconnected during light load hours

Power Transformer

230KV Power Transformer in Gas Plant

Every alternator provide with automatic voltage regulator which perform following function

1. Control of voltage within prescribed limits. 2. Proper division of reactive power b/w alternator

operating in parallel. 3. Prevention of dangerous over-voltage in system. Types Using Transformer Induction Voltage Regulator Now-a-days Electronic voltage regulators are used

for greater sensitivity and accuracy.

Voltage Regulators

Bus bar is a main bar or conductor carrying an electric current to which many connections are to be made.

Usually two buses are provided in a system one is called the “Main” bus and other “Auxiliary ” or transfer bus

There are many shapes of bus bar available like round tubes, round solid bars or square tube

Material used for bus bar is aluminum because it has high corrosion resistance than copper and lower cost.

Bus bar of 5 to 6 meter in length

Bus- Bars

Bus -Bar

Reactor is a coil having large inductive reactance in comparison to its resistance.

It is used in the circuit to limit the short circuit currents to a safer value in order to protect the electrical installation

As their reactance is very small, the efficiency of the system is not affected.

It avoid the faulty current to flow through the healthy system.

Types of reactor 1. Open type 2. Oil Immersed type

Reactors

The porcelain insulators are used to support the bus-bar

It also provide the insulation to the bus-bar from pole to ground

Current rating of porecelain is above 2000A

Post type insulator

Insulators

During the operation of power system the generating plants, transmission lines, distributors and other electrical equipment are required to be switched on and off under both normal and abnormal conditions Switchgears are used

All the protection equipment like switches, fuse, Circuit breakers, relays are installed in switchgear

Types 1. Outdoor type 2. indoor type For the voltage above the 66KV outdoor

switchgears are installed

Switchgear

230KV Switchgear

A switch is a device which is used to making or breaking the electric circuit. By simple motion of a knob or handle

They can make or break the circuit during normal and abnormal conditions

Types 1. Air switches 2. Oil switch Oil switches are used in high voltage and heavy current circuit

Switches

Protective equipment are very important in system to isolate the abnormal conditions

Feature of protective equipment 1. greater reliability 2. High speed of operation 3. Simple and withstand to large value of

fault Various Protective equipment are Fuse, Circuit Breakers, Relays, Lightning

arresters

Protective Equipment

Fuse is a wire of short length or thin strip of material which melt with the flow of excessive current

Under normal working conditions safe value of current flows but during short circuit load current increased which heat the wire so wire melt and circuit break

Advantages:- 1. cheap in cost 2. needs no maintance 3. it interrupts short-circuit current without

noise, flame, gas or smoke.

Fuse

4. Under short circuit condition it limits the current

5. By the use of inverse time characteristic it is easily provided for over load protection.

Disadvantages of fuse:- 1. wire should be replaced after every operation

Rewire able Kit-Kat Fuse

A circuit breaker is a mechnical device used to open and close contact under normal and abnormal conditions

Relay is use as a sensor with circuit breaker for automatic operation

Circuit breaker carry normal current without over- heating or damage

Function of circuit breaker:- 1. To carry full load current continuously 2. To open and close the circuit under no load 3. To break the circuit under short-circuit

condition

Circuit Breakers

According to voltage level 1. Low Voltage CB :- V < 1000Vac , I up to 100A 2. Medium voltage CB:- V up to 72KV , I up to

6300A 3. High voltage CB:- v up to 1200KV , I > 6300A

Miniature Circuit Breaker

Types of Circuit Breakers

Relay is electro-mechnical device which sense the excessive flow of current and send signal to the circuit breaker

Relay has three essential elements 1. Sensing element- it sense and measure

the change 2. Comparing element- compare the

measured quantity to pre-setted value 3. Controlling element- it sends signal to

circuit breaker

Relays

1. Latching relay 2. Reed relay 3. Mercury relay 4. Polarized relay 5. Solid-state relay

Relay

Types of relay

It is an instrument transformer which is used to measure the current from high voltage line with the use of normal ampere meter.

High currents or voltages of electrical power system can not be directly fed to relays and meters. CT steps down rated system current to 1 Amp or 5

The relays and meters are generally designed for 1 Amp, 5 Amp and 110V.

Current Transformer

It is normally a step-down transformer Secondary winding has a 5 ampere value of

current to the rated current of primary winding

It is also a instrument transformer which is used to measure the voltage above 380 volts

PT make the ordinary low voltage instrument suitable for measurement if high voltage and isolate from high voltage.

When rated high voltage is applied to primary of PT, it give the secondary voltage of 110 volts

Potential Transformer

All power plant and sub-stations DC supply for protection and control purpose

DC supply is provided from Storage batteries.

Lead acid battries mostly used in power stations because their higher cell voltage and lower cost

Batteries

Control room is nerve centre of the power station Various controls like Voltage adjustments, load

control, emergency tripping of tubine and other equipment and instruments are housed in the control room.

Location of control room is away from noise and should near to the switch house

There should be no glare , neat and clean, well ventilated and free from draughts

Control Rooms

Control room in thermal power plant

Thank You