Major electrical equipment in power plants

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Transcript of Major electrical equipment in power plants

MAJOR ELECTRICAL EQUIPMENT IN POWER PLANTS

MAJOR ELECTRICAL EQUIPMENT IN POWER PLANTSSubmitted To:- Er. Sonika Singh

Presented By :- Gurdit Singh1184238EE 2k10

Power plant consists of Variety of electrical equipmentMajor 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

Inelectricity generation, anelectric generatoris a device that convertsmechanical energytoelectrical energy. A generator forces electric current to flow through an externalcircuit.Generator are varies in type according to the type power plantGenerator 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.Types1. DC Excitation System 2. AC Excitation System3. Static Excitation SystemExciters

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 changersThey are put in operation during large load hours and disconnected during light load hoursPower Transformer

230KV Power Transformer in Gas Plant

Every alternator provide with automatic voltage regulator which perform following function1. 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.TypesUsing TransformerInduction Voltage RegulatorNow-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 busThere 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 lengthBus- 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 installationAs 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 reactor1. Open type2. Oil Immersed typeReactors

The porcelain insulators are used to support the bus-bar It also provide the insulation to the bus-bar from pole to groundCurrent 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 usedAll the protection equipment like switches, fuse, Circuit breakers, relays are installed in switchgearTypes1. Outdoor type2. indoor typeFor the voltage above the 66KV outdoor switchgears are installedSwitchgear

230KV Switchgear

A switch is a device which is used to making or breaking the electric circuit. By simple motion of a knob or handleThey can make or break the circuit during normal and abnormal conditionsTypes1. Air switches2. Oil switch Oil switches are used in high voltage and heavy current circuitSwitches

Protective equipment are very important in system to isolate the abnormal conditionsFeature of protective equipment1. greater reliability 2. High speed of operation3. Simple and withstand to large value of faultVarious Protective equipment are Fuse, Circuit Breakers, Relays, Lightning arrestersProtective Equipment

Fuse is a wire of short length or thin strip of material which melt with the flow of excessive currentUnder normal working conditions safe value of current flows but during short circuit load current increased which heat the wire so wire melt and circuit breakAdvantages:-1. cheap in cost2. needs no maintance3. it interrupts short-circuit current without noise, flame, gas or smoke.

Fuse

4. Under short circuit condition it limits the current5. 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 conditionsRelay is use as a sensor with circuit breaker for automatic operationCircuit 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 load3. To break the circuit under short-circuit condition Circuit Breakers

According to voltage level1. Low Voltage CB :- V < 1000Vac , I up to 100A2. 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 breakerRelay has three essential elements1. Sensing element- it sense and measure the change2. Comparing element- compare the measured quantity to pre-setted value3. Controlling element- it sends signal to circuit breakerRelays

1. Latching relay2. Reed relay3. Mercury relay4. Polarized relay5. 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 ofelectrical power systemcan 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 transformerSecondary 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 voltsPT 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 houseThere should be no glare , neat and clean, well ventilated and free from draughtsControl Rooms

Control room in thermal power plant

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