Generator Generator ConstructionConstruction

ByBy Ms. Soh Ley BauMs. Soh Ley Bau

Generation Section--Electrical Unit Generation Section--Electrical Unit (ILSAS),TNB(ILSAS),TNB

System OverviewSystem OverviewPrinciple of Thermal Power Plant

System OverviewSystem Overview Principle of Thermal Power PlantPrinciple of Thermal Power Plant

System OverviewSystem Overview

Furnace The chemical energy from fuel is converted to

heat

Back

System Overview System Overview

The heat from the burning fuel causes The heat from the burning fuel causes water in the boiler change to steamwater in the boiler change to steam

Boiler

Back

System OverviewSystem Overview

The steam is sent to the turbine, where it causes the turbine blades to

rotate. The turbine converts the energy

in the steam into mechanical energy.

Steam Turbine

Back

System OverviewSystem Overview

Generator

The turbine shaft connects the turbine to the generator through a coupling and as the turbine rotates,

the generator rotor shaft also rotates.

NextCoupling?Coupling?

Ask meAsk me

System OverviewSystem Overview

GeneratorThen, the generator converts the

mechanical(rotating) energy into electrical energy

NEXT-DEMO

Turbine

Coupling

System OverviewSystem Overview

Generator

Side Turbine side

I get it !!

How the electrical generator How the electrical generator work?work?

How AC How AC generator generator

work?work?

AC AC GeneratorGenerator

Prepared by @ Ms.Soh Ley Bau 13

Single Phase Generator/ Single Phase Generator/ AlternatorAlternator

Types of GeneratorsTypes of Generators

Turbo Generator (Turbo Generator (Cylindrical Cylindrical Rotors)Rotors)

Turbine GeneratorTurbine Generator

Salient pole GeneratorSalient pole GeneratorHydro GeneratorHydro GeneratorDiesel GeneratorDiesel Generator

Salient Pole GeneratorSalient Pole Generator

Salient Pole Generator Salient Pole Generator Hydroelectric PlantHydroelectric Plant

(Chenderoh, Sg Perak)(Chenderoh, Sg Perak)

Salient Pole GeneratorSalient Pole GeneratorStator WindingsStator Windings~ Cameron Highland~ Cameron Highland

Salient Pole Rotor Salient Pole Rotor

A 4 Pole rotor starts as a solid rough forging

The shaft, spider and the 4 poles and pole tips are created by machining away part of the forging.

The strip wound fielding winding is added to complete the rotor

Solid 6 pole machine with Solid 6 pole machine with brushless exciterbrushless exciter

Salient Pole GeneratorSalient Pole GeneratorRotor Pole Rotating Type Exciter

Salient Pole RotorSalient Pole RotorCameron Highland Cameron Highland

Salient Pole Rotor Salient Pole Rotor Kenyir (112MVA, 24 poles)Kenyir (112MVA, 24 poles)

Salient Pole GeneratorSalient Pole GeneratorDiesel Generator

Salient Pole GeneratorSalient Pole Generator6.6kV Black Start Diesel Generator (PD1)

Salient Pole GeneratorSalient Pole GeneratorDiesel Generator,12 poles Diesel Generator,12 poles

WWhat are the hat are the

functions of functions of generator in generator in the Power the Power

Utility Utility Industry?Industry?

IntroductionIntroduction To convert the rotational To convert the rotational

mechanical energy (steam mechanical energy (steam turbine) into electrical energyturbine) into electrical energy

Steam Steam TurbineTurbine

GeneratorGeneratorMain Main exciterexciter

IntroductionIntroduction

To supply energy to the power To supply energy to the power grid and route some power to grid and route some power to

machine auxiliaries (via the machine auxiliaries (via the Unit Transformer)Unit Transformer)

One-line diagram for generator and One-line diagram for generator and generator transformergenerator transformer

Layout of Power PlantLayout of Power Plant

Pressure Rise in a TransformerPressure Rise in a Transformer

Transformer-Phase to Earth Transformer-Phase to Earth FaultFault

Transformer-Phase to Earth Transformer-Phase to Earth FaultFault

Transformer-Phase to Earth Transformer-Phase to Earth FaultFault

Split Generator ShaftSplit Generator Shaft

Generator Main Circuit Generator Main Circuit Breaker (SFBreaker (SF66))

Generator Main Circuit Generator Main Circuit Breaker (SFBreaker (SF66))

Components of GMCBComponents of GMCB

Generator ConstructionGenerator Construction

Stator

Rotor

Bracket

Generator ConstructionGenerator ConstructionMain Components:

– a.)Stator (stationary part)– b.)Rotor (rotating part)– c.)Rotor Bearing– d.)Pilot AC Exciter– e.)Main Exciter– f.)Automatic Voltage Regulator (AVR)– g.) Rotating rectifier– h.)Stator Output Leads and Isolated Phase Bus– i.)Generator Neutral Earthing– j.)Hydrogen Cooling system

StatorStatorStator consists of stator core,stator frame,

slot wedges and etc.Function:-Armature- produce output of the generator

Stator ConstructionStator Construction

-Special explosion proof design- In case any gas explosion inside, it provides a safe tight housing

-MaterialMaterial :No.1 SM41 AP, of JIS G 3106 Rolled Steel for welded Construction and is tested to be free from cracks etc. by a supersonic test

•Stator Frame

Stator ConstructionStator Construction

Stator Stator corecore

WedgeWedge

End winding

Stator ConstructionStator ConstructionStator Core

The functions of stator core are :

a) Concentrate the lines of magnetic flux around the stator windings

b) Support and hold the windings in position around the rotor as the rotor turns.

Stator coreStator core

Figure : Side view of the stator core

*Note : Air-cooled generator in Serdang power station

Stator ConstructionStator Construction Slot Wedge

Function:

The stator windings or stator coils are simply long insulated bars which are assembled and wedged-locked into the stator core slots running length wise through the generator.

Stator ConstructionStator Construction Slot Wedge

Wedge is located on the top of each slot

End winding

Stator ConstructionStator ConstructionStator Lamination

-To form a stator core, high quality silicon steel plates of little core loss are used and punch them with a die in such segments as shown in the illustration.

-After giving them varnish treatment, pile them up on a stator frame.

Stator LaminationStator Lamination

*Stator Core

Stator LaminationStator Lamination

Stator ConstructionStator ConstructionStator core end

Stator ConstructionStator Construction Stator core end Functions: -The coil end is rigidly tied with a glass cord to the micarta

coil support which is bolted to the stator core and laminated core.

(Reason: withstand the immense power at the time of short circuit )

-At the extreme end is placed a resin ring made of epoxy impregnated glass fiber, and molding mixtures are stuffed in the space between the said ring and coil in order to support them.

Effect of the Flexible MountingEffect of the Flexible Mounting

Flexible MountingFlexible Mounting

~ To prevent high level vibration (two-pole machines) from being transmitted to the frame and foundation, the stator core is supported from the frame by a flexible mounting.

~ To support the weight of the core and to withstand short circuit torque.

Flexible MountingFlexible Mounting

Rotor ConstructionRotor Construction

Rotor shaft of an inner cooled Rotor shaft of an inner cooled generatorgenerator

Pole face

Prepared by @ Ms.Soh Ley Bau 65

Rotor ForgingRotor Forging

@soh-Serdang GT5

Rotor ConstructionRotor ConstructionRotor coil

Example of rotor end windingExample of rotor end winding*Serdang Power Station Nov.2003,Unit 2

Rotor ConstructionRotor ConstructionRotor CoilMaterial : cold worked silver bearing

copper

Function: Field coil of the generator

Rotor ConstructionRotor Construction

Coupling at turbine side

Rotor

@Unit 1 SJSSAA,kapar(Oct 03)

Rotor ConstructionRotor Construction

Retaining ring

@Unit 1 SJSSAA,kapar(Oct 03)

Retaining RingRetaining Ring

Function:

~To support the rotor coil end, thin cylindrical coil retaining rings are force fitted to both ends of the rotor body

@Sohlb Serdang GT5

Rotor ConstructionRotor Construction

End windings of the rotor coil

@Unit 1 SJSSAA,kapar(Oct 03)

Generator PartsGenerator Parts

NEXTNEXT

Generator’s Journal BearingGenerator’s Journal Bearing Bearing # 5 (Turbine side)

Bearing # 6

(Excitation side)

NEXTNEXT

@Unit 1 SJSSAA,kapar(Oct 03)

Generator’s Journal BearingGenerator’s Journal Bearing

Function:To support the generator rotor.

(In order to keep the shaft free from undue stress because of deflection of shaft and misalignment, the bearings are of spherical surface which are machined to have a high pressure oil-line,lubricating oil line, etc.

BACKBACK

Bearing BracketBearing BracketTop half of bearing bracket

Bottom half of bearing bracket

Main Exciter side

Rotating Rectifier

NEXTNEXT

@Unit 1 SJSSAA,kapar(Oct 03)

Bearing BracketBearing Bracket

Dismantle the top half bearing bracket using overhead crane

NEXTNEXT

@Unit 1 SJSSAA,kapar(Oct 03)

Bearing BracketBearing Bracket- Welded construction & is directly fixed to the stator frame

- It is divided into two parts both at the turbine side & the exciter side.

- Having sufficient mechanical strength by means of many ribs.

- In the bracket are included bearings, gland seal ring and oil seal and the lower section of the lower bracket constitutes a deforming tank.

- To fix the stator frame, gasket and sealing compounds are used and the construction is such that gas leakage is kept to the minimum.

BACKBACK

Gland seal Gland seal Gas tight enclosure for hydrogen cooled generator

Function:

-To prevent hydrogen gas leakage along the shaft

NEXTNEXT

@Unit 1 SJSSAA,kapar(Oct 03)

Gland sealGland seal

BACKBACK

Seal ringSeal ring

Position of seal ring

Seal ring (Bottom half)

Gland seal

Seal ringSeal ring

BACKBACK

Air Gap BaffleAir Gap Baffle

Air Gap BaffleAir Gap Baffle

Function:Function:

-To separate the -To separate the high pressure and high pressure and the low pressure the low pressure ventilation zones at ventilation zones at the exciter end of the exciter end of the rotor & stator.the rotor & stator.

BACKBACK

BlowerBlower

- Multi-stage axial blower is installed only at turbine side (inner cooled machine)

Function:

-To feed the cooling gas(cold gas) into a long and narrow vent duct in the axial direction ventilation.

NextNext

BlowerBlowerBlower Blade

Material:

Ni-Cr-Mo steel

Cooling Fan/blowerCooling Fan/blower**Unit 5 Port Dickson Power Station****Unit 5 Port Dickson Power Station**

BACKBACK

Blower ShroudBlower Shroud

BACKBACK

Gas cooler/Hydrogen CoolerGas cooler/Hydrogen Cooler

NEXTNEXT

Gas Cooler Hydrogen CoolerGas Cooler Hydrogen Cooler-Two gas coolers are each arranged vertically both on the right side and the left side of the turbine side in the generator.

-Cooling tubes with spiral copper fins are used as shown (b).

-The cold gas temperature is designed to maintain below 45C when the cooling water temperature is 40 C .

(a)

(b)

NEXT

Gas Cooler Hydrogen CoolerGas Cooler Hydrogen Cooler

1. During generator operation, electrical resistance heating in the gen.windings-creates large amount of heat

2. This heat is removed from gen.windings-circulating hydrogen gas through windings

3. Circulation is accomplished by cooling fan.

4. The heat from hydrogen gas is then removed by cooling water flowing through hydrogen coolers

BACKBACK

Generator Generator Exciter System Exciter System Fundamentals Fundamentals

Excitation SystemExcitation System

Functions a.) Supply, control and regulate the amount of field

current applied to the generator field winding, so that the generator output voltage kept constant, at predetermined levels, under varying load conditions.

b.) Allow the operator to change the reactive loading of the machine

Basic Exciter PrinciplesBasic Exciter Principles

Three factorsThree factors which affect the output of a generator.

1. The number of conductorsnumber of conductors (fixed for a particular generator)

2. The speed of rotation of the rotorspeed of rotation of the rotor( fixed at 3000RPM for 2 pole machines operating on a 50Hz system)

3. The strength or density of the magnetic fluxstrength or density of the magnetic flux or field( varied by increasing or decreasing field current)

Types of ExcitersTypes of Exciters

1. Static Type System1. Static Type System AC power directly from the main generator

leads The power taken from the generator leads

is first stepped down through a special transformer and then fed to rectifiers for conversion to dc.

Types of ExcitersTypes of Exciters

2. A-C Generator (Alternator)/PMG 2. A-C Generator (Alternator)/PMG Excited SystemExcited System

The main generator drives an alternator to produce ac power, which is then converted to dc by means of rectifiers.

Static ExcitationStatic Excitation

Static Excitation Static Excitation

If generator voltage not reaches to 60% within 20 sec, initial excitation failure alarm is raised.

30sec20 sec 0 sec

Excitation TransformerExcitation TransformerDry type Excitation Transformer Dry type Excitation Transformer

( 3.44MVA 15/0.88kV)( 3.44MVA 15/0.88kV)

Core Type TransformerCore Type Transformer

PMG Excited SystemPMG Excited System

PhotoPhoto

AC

Advantage of Brushless Excitation Advantage of Brushless Excitation SystemSystem

1. Reliability. “ AC Exciter-Rotating Rectifier” mounted on a common shaft

2. Maintenance cost is reduced because there is no brush, commutator and slip ring

3. There is no troubles of insulation resistance since the adhesion of carbon duct is varnish.

4. All devices are placed in closed housing and not exposed to the atmospheric conditions.

Advantage of Brushless Excitation Advantage of Brushless Excitation SystemSystem

5. Change of brush is needless during operation so that with an increase of safety, the operation can continue for the long term.

6.Generator field breaker,field regulator and exciter bus or cable become unnecessary.

(not required any DC bus duct from excitation transformer to IPB for static excitation)

Advantage of Brushless Excitation Advantage of Brushless Excitation SystemSystem

7. Foundation cost will also reduces since air ducts and exciter bus (Excitation Transformer) are not needed in foundation.

8. It permits continuous conservative operation and tolerates transitory over loads to ceiling voltages.

9. Spare exciter is also unnecessary

GeneratorGenerator

AVR card

Rotating

Rectifier

PMGPMG

Main generator

NEXTNEXT

Brushless Excitation System-Main ExciterBrushless Excitation System-Main Exciter

PMG Rotating Armature

Rotating Rectifier

BackBack

Brushless Excitation System-PMGBrushless Excitation System-PMG

Rotating armature PMG or Pilot Exciter

NEXTNEXT

Permanent Magnet GeneratorPermanent Magnet Generator

PMG StatorPMG Stator

PMG RotorPMG Rotor

NEXTNEXT

Pilot Exciter/PMG/High Pilot Exciter/PMG/High Frequency GeneratorFrequency Generator

PMG= Permanent Magnet GeneratorFunction: To provide a constant source of excitation power

for exciter field via the Automatic Voltage Regulator(AVR) which is the controlling device governing the level of excitation provided to the exciter field

BackBack

Automatic Voltage regulator Automatic Voltage regulator (AVR) Panel (AVR) Panel

Function:

-AVR responds to a voltage sensing signal derived, via an isolating transformer (Potential Transformer) from the main stator winding.

NEXTNEXT

Automatic Voltage Automatic Voltage Regulator (AVR) PanelRegulator (AVR) PanelFunctions:Control the field current in order to

maintain the generator output voltage at a predetermined level, with minimal changes over a wide range of load demand.

Adjusting the Q(Mvar) reactive power

Automatic Voltage Automatic Voltage Regulator (AVR) PanelRegulator (AVR) Panel

Improve the power system stability (transient stability)

Suppress the over generator voltage on the load rejection

BackBack

Exciter Stator & Exciter RotorExciter Stator & Exciter Rotor

Field coil on the stator of main exciter

(Rotating Armature)

NextNext

Exciter Stator & Exciter RotorExciter Stator & Exciter Rotor

Function:-As an AC Generator (Rotating Armature)-Exciter Stator-Create magnetic field-Exciter Rotor-Induced current

BackBack

Rotating RectifierRotating Rectifier

Function:AC to DC Converter-To provide excitation

(DC supply) into the main rotor

BackBack

?? ????

Excitation with carbon brushExcitation with carbon brushSJTJ,Unit 5~2003SJTJ,Unit 5~2003

Cartridge TypeCartridge TypeSJTJ,PD1 2004SJTJ,PD1 2004

Slip Ring BrushGearSlip Ring BrushGear

Slip RingSlip Ring

Prepared by Ms.Soh

Stator Terminal Box and Stator Terminal Box and BushingBushing

Terminal BoxTerminal Box

Stator TerminalStator Terminal

Bushings

Function:

- To route the electricity produced in the stator windings

Isolated Phase systemIsolated Phase system

Function:

-The output of the stator is connected to the generator transformer via an isolated Phase Bus (IPB) system

Isolated Phase systemIsolated Phase system

•Required high reliability

•Made of high quality materials and welded constructions are adopted.

•Dry air is constantly feed into IPB bus through the air supply equipment

•Prevent external air from flowing into IPB

•Prevent the inside of IPB from dewing

Generator Neutral EarthingGenerator Neutral Earthing

Function:Function:• To limit the stator To limit the stator

earth fault current earth fault current that can flowthat can flow

• (to prevent the earth fault (to prevent the earth fault current flow through the core of current flow through the core of the generator)the generator)

Generator Transformer & Generator Transformer & TransmissionTransmission

Generator Transformer (11kV/275kV)

Transmission side (switchgear) 275kV

Note:*PD power station

Seal Oil SystemSeal Oil System

Seal Oil SystemSeal Oil System

Function:-To lubricate the seals and prevent

hydrogen from escaping from the generator without introducing an excessive amount of air and moisture into the generator

Hydrogen cooling systemHydrogen cooling system(Inner Cooling)(Inner Cooling)

Figure :Longitudinal sectional view of generator

Characteristics of Hydrogen CoolingCharacteristics of Hydrogen Cooling Table 1:

  Air  

Hydrogen

Density 

1.00 0.07

Thermal conductivity 

1.00 7.00

Heat Transfer coefficient from surface gas 

1.00 1.35

Specific heat 1.00 0.98 

Support of combustion Yes 

No

Oxidizing agent 

Yes No

Prepared by @ Ms.Soh Ley Bau 132

Serdang GT5

Siemen

Prepared by Ms. SOh

Prepared by Ms.Soh

Prepared by Ms.Soh

Prepared by @ Ms.Soh Ley Bau 133

Serdang GT5

Siemen

Prepared by Soh

Prepared by @ Ms.Soh Ley Bau 134

Characteristics of Hydrogen CoolingCharacteristics of Hydrogen Cooling

An ideal cooling mediumAn ideal cooling mediumThe combination of low density and high specific heat of hydrogen

Lower effectiveness of air as a cooling mediumLower effectiveness of air as a cooling medium (requires a 20% to 30% size increases over a hydrogen cooled machine a similar rating).

Design for higher electrical loadingDesign for higher electrical loading compared to the air –cooled machine due to better cooling.

Hydrogen Inner-cooling Hydrogen Inner-cooling systemsystem

To remove heat directly from the stator and rotor conductors by hollowing them and flowing a high velocity gas through these hollows

Advantages:– Sharply increase output in similar size– Possible to employ higher hydrogen gas pressures

than a conventional hydrogen cooled unit

AcknowledgementAcknowledgement

Mr. Low Siew Wooi,JPSMr. Low Siew Wooi,JPSMr. Foo Hi Kium, ILSASMr. Foo Hi Kium, ILSASMr. Mok Kin Wah,ILSASMr. Mok Kin Wah,ILSASMr. Lew Kar Wong, SJTJMr. Lew Kar Wong, SJTJMr. Thong Lit Yen, TNBHMr. Thong Lit Yen, TNBH