Turbine & GeneratorR.Rajendra kumar

Steam turbine is a machine which derives its energy of rotation due to -

conversion of the Heat energy of the steam into kinetic energy -

when it expands through a series of nozzles mounted on the casing or by the fixed blades INTRODUCTION

WORKING PRINCIPLESteam inSteam outForce F

CLASSIFICATION OF STEAM TURBINE Based on the action of steam Based on the heat balance arrangement Based on steam condition at inlet to turbine Based on shaft arrangement Based on direction of steam flow

COMPONENTS OF STEAM TURBINE

CASING OF STEAM TURBINETurbine casing is an outer cover of the turbine which has capability to withstandThe maximum pressure and temperature Produced within it.

The cylinder must be extremely stiff in Longitudinal direction to avoid bending

CASING

ROTOR OF STEAM TURBINEMoving bladeRotor is a rotating device where the movingblades are mounted in it and the extended Shaft is coupled to the generatorFACTOR:Critical speedROTOR

BLADES OF STEAM TURBINEIts the component which is responsible for Actuating the rotorSHROUDAERO FOIL TRAILLING EDGE AERO FOIL LEADING EDGEROOT

TURNING GEAR FOR STEAM TURBINEMeshing motorChain driveMeshing hand wheelTurbo generator shaftMeshing leverControl valveTurning gear is a device provided To rotate the turbine shaft slowlyDuring the pre startup and shut downPURPOSE :To prevent the uneven heatingAnd cooling of shaft which may Lead to misalignment and bending Of shaft

COUPLINGS FOR STEAM TURBINE

In turbines we are making use of three types of couplings

1.Flexible coupling capable of absorbing small angular misalignments & axial movement.

Claw coupling

Bibby coupling up to medium sizes, provides torsional resilience Multi tooth transmits torque by internal & external gear teeth , curved to accommodate angular misalignment.:

Contd . SEMI FLEXIBLE COUPLING mainly used b/w turbine& generator. It needs no lubrications

RIGID COUPLINGS These are used at a high torque places, joined by number of fitted bolts.

SYSTEMS OF STEAM TURBINEGLAND SYSTEMCONDENSATEOIL SYSTEMGOVERNING TURBINE SYSTEM

GOVERNING SYSTEMPURPOSE :To maintain the speed of the turbine during fluctuation of load on the generator by Varying steam input to the turbine to produce the Electricity at 50Hz frequency

GOVERNINGMAJOR COMPONENTS Speed governor with pilot valve Speeder gear or Load- speed changer Load limiting gear

TURBINE OIL SYSTEMPURPOSE : To create oil wedge in the journal while rotating To maintain the temp of bearings Medium for a hydraulically operating governor gear Sealing medium for hydrogen cooled generatorsMAINCOMPONENTS Main oil pump Starting oil pump A.C Lub oil pump D.C.Emergency oil pump Oil tank Drain valve Oil pressure drop relay Oil Coolers

GLAND SYSTEMPURPOSE :To prevent or reduce the leakage of steam or air between rotating and Stationary components which have a pressure difference across them Even though various glands systems are there in recent we are using LABYRINTH GLANDSTAGEREDRESILIENTVERNIER

AXIAL SHIFTHPIPLPGENBPBPBPBP MOVABLE BASE PLATE MOVABLE BASE PLATETHRUST BEARING FIXED BEARING PED, FIXED BEARING PED,AXIAL SHIFT Thrust bearings are provided in the front bearing pedestal of HP & IP turbines. This pedestals are free to slide on the baseplate . The rotor expansion of IP & HP moves towards the front bearing pedestal of HP. The movable baseplate accommodate the axial shift of the HP & IP rotor.BP BASE PLATE

EXIT TO TURBINE

GENERATORThe machine which generates alternating currents is known as an alternator,

also called as synchronous generatororThe machine which converts the mechanical energy into electrical energy

WORKING PRINCIPLEWhenever the conductor cuts the magnetic flux then some emf induced in the generator, A.C generator commonly called as alternator - no commutators MAIN COMPOPNENTS Stator RotorContains 3 armature windingsContains field windingsSYSTEM Excitation system Cooling system Protection system

STATOR The stator is the component that contains : Armature core Armature winding Its totally enclosed gas tight fabricated structure CORE It contains large number of core sections (packets) Its size approximately 0.35mm 0.5mm These packets are used for cooling of the core by hydrogen

STATORContd .WINDINGS It has 3 armature windings provided Stator core carries the armature winding where the voltage is generated due to Electro magnetic induction Each stator conductor must be capable of carrying the rated current without over Heating and the insulation must be sufficient to prevent the leakage current flowing Between the phases to earth Windings for the stator are made up from copper strips with insulated tape

ROTOR The rotor caries the field winding Silver bearing copper (containing 0.03 0.1% of silver) is used for the windings with mica As the insulation between the conductors It revolves in higher speed There is a hole through out the length, for cooling purpose. To the other end of the rotor exciter is coupled.

TYPES OF ALTERNATORRevolving armature type (stator)Revolving field type (rotor) It has stationary field poles and stator rotating type only used for small KVA capacity and low voltage rating It has stationary stators and rotor will rotates Most of the alternators are used revolving field type

TYPES OF ALTERNATORContd .ADVANTAGES OF REVOLVING FIELD (ROTOR) Field has less weight The stator ( armature) winding must be insulated for a high voltage ( armature winding is easily insulated up to 30 KV) The load currents are easily taken out from the fixed terminal of stator

OTHER TYPES OF ALTERNATORBased on construction :Salient pole alternator This type of alternators are used where the prime mover is capable of running at slow speed This prime mover ranges between 120 rpm to 600 rpm This type of alternator has higher number of poles so speed of the alternator is low Non salient pole type This type of alternator are used where the prime mover is capable of running at high speed Speed ranges above 1000 rpm Normally two or four poles are used

EXCITATIONThe rotor generates magnetite field ,a direct current supply is Required to energies the winding and the rotor ,this is usually supplied by the direct current Generator known as an excitatorIt may be directly coupled to the rotor shaft or through a gear box EXCITATIOND.C SYSTEMRECTIFIED A.C SYSTEM( BY USING THYRISTOR)

EXCITATIONContd .In modern developments is to replace the D.C generator with an A.C. generator, the out put ofWhich is passed through rectifiers to give a D.C supply to the rotor windings other method is to tap A.C from generator terminals and then rectify through thyristor And supplied Cooling The excitor is air cooled The hot air is cooled in two coolers arranged to the sides of excitors The excitors receives the cool air from the fan and passes inside the exciters

INDUCED VOLTAGEThe rotating field flux cuts the three phase armature winding of the alternator . The magnitude of the induced e.m.f EMF/ phase = 4.44 f t volts EMF/ line = 3 * 4.44 f t volts Flux per polefFrequency of the induced emftTurns per phase

SPEED OF ALTERNATORThe speed of the alternator depends on poles and frequency N = 120f / p P = no of polesF = frequency of generatorIn Indian standard the frequency is 50 Hz (CONSTANT)The frequency tolerance + or 5% that is 47.5 to 52.5

LOSSES IN ALTERNATORAlternator under working & stationary condition and following losses are occurred Core loss Copper loss Armature copper loss Field copper loss Mechanical loss Frictional loss

COOLING OF ALTERNATORNEED :Many losses are occurred in the alternator , these losses are converted into heat so temperature of the machine increases so cooling is adopted METHODS : : Open system using air Air is taken from the atmosphere and passes through the machine by using pumpThis method only used up to 3MW Hydrogen coolingHydrogen is passed through a alternator by using pump For large capacity machine used only hydrogen cooling method This method Is best one

COOLING OF ALTERNATORContd .CONDITION : The hydrogen must be pure one The complete machine should be designed with gas tighten casing with proper sealsADVANTAGES : Reduction of noises because the machine runs in gas tighten casing This system is capable of performing the following functions : Filling in and purging out of hydrogen safely with out bringing any contact with air Automatic maintenance of hydrogen gas pressure inside the generator Indication to the operator about the condition of the gas inside the generator that is Pressure , temperature and purity Indication of liquid level in generator and alarm in case of high level

EFFICENCY OF ALTERNATOREFFICENCY = Output / (Output+ LOSSES) = KVA * PF / (( KVA * PF) + LOSSES) POWER FACTOR = THE ANGLE BETWEEN THE VOLT & CURRENT

FAULTS IN ALTERNATORFAILURE OF PRIME MOVERFAILURE OF EXCITORSFAILURE OF INSULATION IN WINDINGSINTER PHASE SHORT CIRCUITINTER TURNS FAULTS IN STATOROVER VOLTAGE

Thank you