MA- Main Generation Flashcards
What is the purpose of the main generator?
Converting mechanical, rotational energy to electrical energy
How does the main generator interface with NK?
Provides power for the generator protection system
How does the main generator interface with the MB (excitation and Voltage regulation system)?
Provides regulated DC voltage to the MA system generator for field excitation
Provides trip signals to the MA generator trip logic
What are the major components of the main generator?
Stater frame, stater, rotor, Generator support
What type of generator is the main generator? How does it work?
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.
What Is the purpose, operation and location of the stater frame?
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
What is in the lower frame extension of the main generator?
The main leads come down through this section which includes bushings, lower leads and insulators
How many windings does the secondary side of the unit aux transformer, MAN-X02, have?
Two
What are the necessary components to produce an electrical current in a conductor?
Field, conductor, and relative motion
Why is it necessary to add mechanical energy above and beyond that needed to overcome friction to the rotor to keep it rotating?
The current generated in the stator creates a magnetic field which interacts with, and opposes, rotation of the rotors magnetic field
How does the main generator (MA) interface with the GH system?
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
How does the main generator interface with the generator lube oil system (LO)?
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.
How does the main generator interface with the generator seal oil system (SO)?
Controls the atmospheric leakage of the generator hydrogen gas at the annulus between the rotor shaft and the generator casing.
Maintains hydrogen purity
How does the main generator interface with the main turbine system (MT)?
Provides the motive power for the generator
Provides valve position signals to the MA system for generator trip logic
How does the main generator interface with the NA system?
NA receives 13.8kV power from the unit aux. transformers
How does the main generator interface with the NG system?
MA system cooling units are powered, normal and alternate sources, from NG
How does the main generator interface with the Remote Multiplex System (MX) system?
MA provides billing metering output and net MW and MVAR outputs
How does the main generator interface with the Stator cooling water system (CE) system?
Provides deionizing cooling water for the main generator stator windings, generator lower frame housing, generator bushings and the rectifier excitation system
what is the purpose of the Stator?
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
what is the purpose, operation and location of the rotor?
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.
what is the purpose, operation and location of the isolated phase bus?
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
what is the primary heat sink for the isophase busses?
turbine cooling water
If isophase bus cooling is lost, how long can rated current be maintained for without causing damage?
30 minutes
there is a hydrogen detection system for the isophase busses. What does high hydrogen concentration in the isophase bus ducts mean?
leakage of hydrogen from the generator stator through the main lead bushings
what is the purpose operation and location of the unit aux transformer?
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
how many alarm point annunciators are on the unit aux transformer?
11
what is the purpose, operation and location of the main transformers?
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
On the main transformers, what is the maximum allowable temperature difference between the oil temp. and the winding temp.?
12C or 53F
How many alarm point annunciators are on the main transformers?
13
what is the purpose, operation and location of the 525kV generator output breakers?
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
what is the purpose of the main generation excitation and voltage regulation?
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
In the main generator, where does excitation power come from during start up before the field is flashed?
non-class MCC, rectified from AC to DC.
In the main generator, where does excitation power come from after the magnetic field has been flashed?
when the magnetic field is flashed, voltage is induced into the stator and the generator provides its own excitation power.
what are the two different methods of regulator control and what controls them?
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
what is the purpose, operation and location of the excitation dome?
purpose:
operation:
location:
what cools the generator hydrogen coolers, excitation transformers and reactors?
turbine cooling water
what is the purpose and capabilities of the main generation excitation and regulation system (EX2100e and Mark VIe) and what are the locations?
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)
What is the operation of the EX2100e power bridges (SCR full wave rectifiers)?
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
What is the output voltage of the PPT (power potential transformers)?
1050VAC
in the EX2100e power bridges, how many Silicon Controlled Rectifiers can be removed during operation?
one
In the SCRs, what controls the gate signal to turn “on” or “off” the SCR?
the voltage regulators
describe the normal operation of the main generator system.
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
how does a loss of the main generator Impact the plant?
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)
How does the MA system respond when it loses support systems?
generator trip, other than losing C02