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NLO Systems NLIT exam 1 > MA- Main Generation > Flashcards

MA- Main Generation Flashcards

1
Q

What is the purpose of the main generator?

A

Converting mechanical, rotational energy to electrical energy

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2
Q

How does the main generator interface with NK?

A

Provides power for the generator protection system

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3
Q

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

A

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

Provides trip signals to the MA generator trip logic

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4
Q

What are the major components of the main generator?

A

Stater frame, stater, rotor, Generator support

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5
Q

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

A

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.

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6
Q

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

A

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

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7
Q

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

A

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

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8
Q

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

A

Two

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9
Q

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

A

Field, conductor, and relative motion

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10
Q

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

A

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

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11
Q

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

A

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

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12
Q

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

A

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.

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13
Q

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

A

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

Maintains hydrogen purity

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14
Q

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

A

Provides the motive power for the generator

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

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15
Q

How does the main generator interface with the NA system?

A

NA receives 13.8kV power from the unit aux. transformers

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16
Q

How does the main generator interface with the NG system?

A

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

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17
Q

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

A

MA provides billing metering output and net MW and MVAR outputs

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18
Q

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

A

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

19
Q

what is the purpose of the Stator?

A

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

20
Q

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

A

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.

21
Q

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

A

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

22
Q

what is the primary heat sink for the isophase busses?

A

turbine cooling water

23
Q

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

A

30 minutes

24
Q

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

A

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

25
Q

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

A

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

26
Q

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

A

11

27
Q

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

A

purpose/operation:
steps up the 24kV off the main generator to 525kV into the switch yard.

forced oil and air cooled
70C/75C
cooling system power provided by 480VAC (norm. and alt.)

location:
outdoors, south side of the turbine building

28
Q

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

A

12C or 53F

29
Q

How many alarm point annunciators are on the main transformers?

A

13

30
Q

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

A

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

31
Q

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

A

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

32
Q

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

A

non-class MCC, rectified from AC to DC.

33
Q

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

A

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

34
Q

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

A

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

35
Q

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

A

purpose:

operation:

location:

36
Q

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

A

turbine cooling water

37
Q

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

A

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)

38
Q

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

A

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

39
Q

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

A

1050VAC

40
Q

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

A

one

41
Q

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

A

the voltage regulators

42
Q

describe the normal operation of the main generator system.

A

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

43
Q

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

A

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)

44
Q

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

A

generator trip, other than losing C02

NLO Systems NLIT exam 1 (8 decks)

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