A SEMINAR ON Different types of Transformers used for 210MW Unit Thermal power plant

A SEMINAR ON

Different Types Of Transformers Used For 210MW Unit Thermal Power Plant

PRESENTED BY :VAIBHAV BHOPE PRITAM BIJWALSUMIT VINCHURKARSANTOSH VIJEKARNIKHIL WANDHARENIKHIL SHRIWASAKASH SHEGOKARCHETAN ANGARWARVIKASH SINGHAKSHAY SAHARE

Overview

IntroductionSingle line diagramClassification of transformerParts of transformerCooling systemProtection of Transformer

TRANSFORMER

Transformer is a static device which transform electric power of one circuit to another circuit without changing its frequency.

Working Principle of transformer :Theworking principle of transformerdepends uponFaradays law of electromagnetic induction. Actually mutual induction between two or more winding is responsible for transformation action in an electrical transformer.

Faradays laws of Electromagnetic Induction:According toFaradays law,

Rate of change of flux linkage with respect to time is directly proportional to the induced EMF in a conductor or coil".

Single line diagram

Types of Transformers used in 210MW unit

1) Generator Transformer 2) Station Transformer 3) Distribution Transformer 4) Unit auxiliary Transformer5) Instrument Transformer 6) Rectifier Transformer 7) Neutral ground Transformer8)Transformer used for general purposes and for different processes. i ) Welding Transformer ii ) Specially designed Transformer used for X ray, Radio, Telecommunication, T.V., High frequency heating, and Industrial heating for different processes.

GENERATOR TRANSFORMER

Generator Transformer Rating

MVA= 240 MVAPrimary Side= 15.75 KV (d)Secondary Side= 400 KV (Y)Oil Qty= 43 KLCooling = OFWFVector Group = Yd11%Z= 11.90

Functions

This is step up transformer of high voltage capacity.This is connected after the generator to step up voltage from 15.75kv to 400kv.The main function of this transformer is to step up voltage so as to reduce transmission losses, line drop and increases Transmission efficiency .

STATION TRANSFORMERStation Transformer Rating

MVA= 40 MVAPrimary Side= 220 KV (Y)Secondary Side= 6.6 KV (Y)Oil Qty= 30 KLCooling = ONAFVector Group= Yy0%Z= 11

FunctionsTransformer at the generating station is required for starting of the generating units when they are either newly constructed or taken of the bar for overhaul.

These Power transformers are called station transformer, which receives power from the grid and feed power-to-power station distribution system.

UNIT AUXILIARY TRANSFORMERUnit Auxiliary Transformer Rating

MVA= 20 MVAPrimary Side= 15.75KV (d)Secondary Side= 6.6 KV (Y)Oil Qty= 6.4 KLCooling = ONAFVector Group= Dy1%Z= 9.0

Functions The Purpose of Unit auxiliary Transformer is to feed power to generator auxiliaries of that unit These transformers are connected to generators and are used as stepping down transformers. The HV side transformer voltage corresponds to the voltage of the generating unit and the LV side voltage is stepped down to 6.6KV Rated KVA of Unit Auxiliary Transformers is approximately 15% of the generating rating Usually these transformers are outdoor transformers One Unit auxiliary transformer is present for every generating unit.

A Rectiformer is a rectifier and transformer designed and built as a single entity for converting alternating current into direct current. It is piece of power systems equipment rather than an electronics component.

Rectiformers are used for supplying power to different field of ESP (electrostatic precipitator).RECTIFORMERFor metering and protection to maintain instrument accuracy. For sensing H.T. side current at the secondary sideUsed in protection relay, trip coils and pilot wires. Used in current power measurement, temperature sensing etc. Current Transformer (CT) Potential Transformer (PT)

INSTRUMENT TRANSFORMERS

CURRENT TRANSFROMER

POTENCIAL TRANSFORMERDISTRIBUTION TRANSFORMER

Distribution transformer

This is step down transformer connected according to applications such as boiler ,turbine , station service board.The main function of this transformer is to provide convenient amount of power in the various boards.

NEUTRAL GROUNDING TRANSFORMERNGTThe subject of grounding covers the problems relating to the conduction of electric current to the earth and through the ground. The earth rarely serves as a part of the return circuit, being used mainly for fixing the potential of circuit neutrals.

The ground connection improves service continuity and protects lives and equipment.

(a) Arcing rounds are reduced or eliminated.(b) The neutral grounding stabilises the neutral point.(c) By employing resistance or reactance in earth connection, the earth fault current can be controlled.(d) The over voltage surge due to lightening are discharged to earth hence less damages to the equipment. Useful amount of earth fault current is required to operate earth faultrelay.(e) Improved service reliability due to limitation of arcing ground and prevention of unnecessary tripping of circuit breakers.(f) Life of eqipment, machines and installation is improved due to limitation of voltages.(g) Greater safety to personnel and equipment due to operation of fuses or relay on earth fault and limitation of voltages. Hence it is economical to ground neutral point.Advantages of Neutral Grounding Transformer

Constructional Features

Main TankLaminated coreCore windingBushingTap changerConservatorBreatherExplosion vent / Pressure relief valve

BREATHER

CONSERVATOR

BUCHHOLZ RELAY

BUCHHOLZ RELAY

Explosion Vent / Pressure Relief Valve

Oil filled bushingsArching horns

Lightening ArrestorCooling system is required for transformer to take away the heat generated in transformer due to losses and maintaining insulation healthy.

Cooling system of transformer is provided by considering design and KVA rating of a transformer. Cooling system of transformer is as follows.i. Air natural cooling system.ii. Oil natural cooling system with or without radiator.iii. Cooling of transformer improved by force airflow by blowers/Air blast by fansiv. Oil forced natural cooling system (OFN): - circulation of oil by pump to radiator, which has natural cooling.v. OFB : Forced oil circulation of oil by pump to radiator, which has force, cooled by air blower.vi. OFW : Forced circulation of Oil through oil cooler and water-cooling is by water.

Generally Oil temp is maintained in between 45 to 55 Dc. & Winding temp in between 55to 80 c.(depends upon insulation class)

Cooling System

Types of Cooling

ONANONAF

OFAF

OFWFMaintenance

Transformer Oil Level CheckingBreather condition monitoringOil testingD. G. A.Oil FiltrationBushing CleaningDrying Out (after 7 Yrs)

Thank you