MA- Main Generation

Question 1

What is the purpose of the main generator?

Answer 1

Converting mechanical, rotational energy to electrical energy

Question 2

How does the main generator interface with NK?

Answer 2

Provides power for the generator protection system

Question 3

How does the main generator interface with the MB (excitation and Voltage regulation system)?

Answer 3

Provides regulated DC voltage to the MA system generator for field excitation

Provides trip signals to the MA generator trip logic

Question 4

What are the major components of the main generator?

Answer 4

Stater frame, stater, rotor, Generator support

Question 5

What type of generator is the main generator? How does it work?

Answer 5

It’s a revolving field AC generator in which direct current From the excitation system Is passed through windings on the rotor by means of slip rings and brushes.

Question 6

What Is the purpose, operation and location of the stater frame?

Answer 6

A gas tight construction that supports and encloses the stator windings, core and rotating field.

Also directs hydrogen throughout the generator through multiple paths

Outer end shields supports the generator rotor bearing, hydrogen shaft seals and oil passages

Inner end shields separate the gas entering the fans from the gas discharged from the fans

Question 7

What is in the lower frame extension of the main generator?

Answer 7

The main leads come down through this section which includes bushings, lower leads and insulators

Question 8

How many windings does the secondary side of the unit aux transformer, MAN-X02, have?

Answer 8

Two

Question 9

What are the necessary components to produce an electrical current in a conductor?

Answer 9

Field, conductor, and relative motion

Question 10

Why is it necessary to add mechanical energy above and beyond that needed to overcome friction to the rotor to keep it rotating?

Answer 10

The current generated in the stator creates a magnetic field which interacts with, and opposes, rotation of the rotors magnetic field

Question 11

How does the main generator (MA) interface with the GH system?

Answer 11

Transmits hydrogen from the service gases system (GA) to the generator and maintains the hydrogen quantity and quality

Hydrogen provides cooling medium for the generator rotor

Purging of the generator for maint. Is received from the CO2 portion of the GH system

Question 12

How does the main generator interface with the generator lube oil system (LO)?

Answer 12

Supplies lube/lift oil to the main generator and exciter bearings.

Provides a low pressure supply of seal oil upon a loss of the main seal oil pumps.

Question 13

How does the main generator interface with the generator seal oil system (SO)?

Answer 13

Controls the atmospheric leakage of the generator hydrogen gas at the annulus between the rotor shaft and the generator casing.

Maintains hydrogen purity

Question 14

How does the main generator interface with the main turbine system (MT)?

Answer 14

Provides the motive power for the generator

Provides valve position signals to the MA system for generator trip logic

Question 15

How does the main generator interface with the NA system?

Answer 15

NA receives 13.8kV power from the unit aux. transformers

Question 16

How does the main generator interface with the NG system?

Answer 16

MA system cooling units are powered, normal and alternate sources, from NG

Question 17

How does the main generator interface with the Remote Multiplex System (MX) system?

Answer 17

MA provides billing metering output and net MW and MVAR outputs

Question 18

How does the main generator interface with the Stator cooling water system (CE) system?

Answer 18

Provides deionizing cooling water for the main generator stator windings, generator lower frame housing, generator bushings and the rectifier excitation system

Question 19

what is the purpose of the Stator?

Answer 19

generates the voltage and current supplied to the unit auxiliary transformer and the main transformers

armature winding is formed by inserting insulated bars into the core slots and joining the ends to form coils each bar is hollow to allow stator cooling water to flow through them

Question 20

what is the purpose, operation and location of the rotor?

Answer 20

it produces the magnetic flux.

flux strength is determined by the number of turns in the rotor winding and current in the winding. DC voltage (excitation) is ran through the rotor.

Question 21

what is the purpose, operation and location of the isolated phase bus?

Answer 21

Purpose:
supplies power to the unit aux. transformer and the main transformers at 24kV.

operation:
the three generator phases exiting the generator are isolated and air cooled to reduce the heat generated by bus losses.

there are three aluminum conductors with porcelain insulators and cooled by the isophase bus cooling system,.

location:
runs from the generator on the 176’ turbine building, out and down the south side of the turbine building to the unit aux transformer, main transformers and MB transformers

Question 22

what is the primary heat sink for the isophase busses?

Answer 22

turbine cooling water

Question 23

If isophase bus cooling is lost, how long can rated current be maintained for without causing damage?

Answer 23

30 minutes

Question 24

there is a hydrogen detection system for the isophase busses. What does high hydrogen concentration in the isophase bus ducts mean?

Answer 24

leakage of hydrogen from the generator stator through the main lead bushings

Question 25

what is the purpose operation and location of the unit aux transformer?

Answer 25

Purpose: provides power from the generator to the non vital loads. operation: steps down 24kV to 13.8kV to supply NAN-S01/02 air and forced air cooling supplied by 480VAC non class power(normal and alternate) location: south side, outside the turbine building

Question 26

how many alarm point annunciators are on the unit aux transformer?

Answer 26

12 point alarm panel for local alarm indication where 1 common alarm will be sent to Control Room

Question 27

what is the purpose, operation (cooling) and location of the main transformers?

Answer 27

purpose/operation: steps up the 24kV off the main generator to 525kV into the switch yard. forced oil and air cooled 70*C/75*C cooling system power provided by 480VAC (norm. and alt.) location: outdoors, south side of the turbine building

Question 28

On the main transformers, what is the maximum allowable temperature difference between the oil temp. and the winding temp.?

Answer 28

12*C or 53*F

Question 29

How many alarm point annunciators are on the main transformers?

Answer 29

12-point annunciator for local indication Each of 12 points has: lamp with lights for associated alarm & three position switch (ON/OFF/TEST)

Question 30

what is the purpose, operation and location of the 525kV generator output breakers?

Answer 30

purpose/operation: generator is connected to the grid through a motor operated disconnect switch and two 525kV breakers disconnect can be operated from CR or locally and allows output breakers to close for re-ringing provide elec. protection trips for the generator on faults on the generator or the grid location: SRP switch yard

Question 31

what is the purpose of the main generation excitation and voltage regulation?

Answer 31

supplies excitation power for the generator and controls output voltage from start up to rated operation. there has to be power to the rotor to establish a magnetic field. controlling the amount of current supplied to the rotor controls the amount of voltage induced in to the stator

Question 32

In the main generator, where does excitation power come from during start up before the field is flashed?

Answer 32

non-class MCC, rectified from AC to DC.

Question 33

In the main generator, where does excitation power come from after the magnetic field has been flashed?

Answer 33

when the magnetic field is flashed, voltage is induced into the stator and the generator provides its own excitation power.

Question 34

what are the two different methods of regulator control and what controls them?

Answer 34

AC regulation- the generator output is sensed and a regulator automatically controls the DC field current to maintain the generator output voltage DC regulation- the operator sets a certain DC field voltage and it remains constant regardless of the output voltage

Question 35

what is the purpose, operation and location of the excitation dome?

Answer 35

purpose: contains generator hydrogen distribution tubes operation: TC cools hydrogen in the main generator via the main generator hydrogen coolers in the excitation dome location: mounted on stator frame

Question 36

what cools the generator hydrogen coolers, excitation transformers and reactors?

Answer 36

turbine cooling water

Question 37

what is the purpose and capabilities of the main generation excitation and regulation system (EX2100e and Mark VIe) and what are the locations?

Answer 37

provide voltage and current to the field of the generator. power for the exciter is drawn from a power potential transformer connected to the generator terminals. line current and stator output voltage are the feedbacks to the exciter the SCR bridge circuit output is controlled by phase and firing signals are generated by digital regulators in the controller electronics are located in the PCR (building on the ground south side turbine building)

Question 38

What is the operation of the EX2100e power bridges (SCR full wave rectifiers)?

Answer 38

Four power bridges receive 1050VAC, each bridge has six silicon controlled rectifiers (SCR) each rectifier has a disconnect switch for removal multi-layered semi conductor device similar to a thyristor, which is a four layer semi conductor (P-N-P-N) and is unidirectional Can be made to operate as an open circuit switch or a rectifying diode depending on how gate is triggered

Question 39

What is the output voltage of the PPT (power potential transformers)?

Answer 39

1050VAC

Question 40

in the EX2100e power bridges, how many Silicon Controlled Rectifiers can be removed during operation?

Answer 40

one

Question 41

In the SCRs, what controls the gate signal to turn "on" or "off" the SCR?

Answer 41

the voltage regulators

Question 42

describe the normal operation of the main generator system.

Answer 42

during start up, pressurize generator with hydrogen start isophase bus and generator stator cooling bring turbine up to speed and apply field excitation energize main transformer (and phase 1 transformer cooling starts) sych generator to 525kV system and load 65MW close second 525kV breaker and load generator transfer NAN-S01/02 busses to unit aux transformer

Question 43

how does a loss of the main generator Impact the plant?

Answer 43

NAN-S01/02 fast bus transfer to off-site power steam bypass control, reactor power cutback and CEDMCS systems will operate to control reactor power (if these fail, reactor trip may occur)

Question 44

How does the MA system respond when it loses support systems?

Answer 44

generator trip, other than losing C02