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Generator Control Relay, which is normally closed, and
through a rectifier.
When the generator starts running, the Permanent
Magnetic Generator supplies the GCU.
The exciter field current is reduced inside the GCU
until 335 Hz is obtained.
As the PMG frequency is below the threshold, the
generator excitation is reduced through the excitation
control module.
The voltage regulation shutdown signal, generated by
the protection module, triggers the voltage regulation
shutdown control module which simulates a high
generator load signal via the current limit module.
As soon as the PMG frequency is over the threshold,
the generator excitation is regulated normally.
The excitation current depends on the comparison
between the voltage sensed at the Point Of Regulation
(POR) and a reference voltage.
As the parameters are correct, the Generator Line
Contactor closes.
The generator excitation also depends on the load.
If a fault is detected by the GCU protection module,
the voltage regulation shutdown control module
simulates a high generator load signal. The exciter
field coils are no longer supplied.
NOTE: the GCR and the GLC are tripped.
TMUELAL01-T02 LEVEL 3
EFFECTIVITY 24-22-00
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AC GENERATION - GENERATOR CONTROL UNIT (GCU 1/2) D/O - VOLTAGE REGULATION
TMUELAL01-P02 LEVEL 3
EFFECTIVITY 24-22-00
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AC GENERATION - GENERATOR CONTROL UNIT (GCU 1/2) D/O
CONTROL AND PROTECTION
The generator control and protection functions are
mainly provided by means of the Generator Control Relay
and the Power Ready relay.
The GCR controls the generator excitation. The PR
controls the Line Contactor and activates the
corresponding warning.
ENGINE FIRE AND OPEN FEEDER CABLE PROTECTION
The feeder cable is duplicated from the engine pylon
to the forward cargo compartment. Each cable is
monitored by a Current Transformer and a sensor.
If an open parallel condition exits, or if the Engine
Fire pushbutton is released out, the GCU trips the GCR
and the GLC and turns off the voltage regulator.
The Ground Power Control Unit (GPCU) determines whether
a fire trip or an open cable trip has occured.
TMUELAL01-T03 LEVEL 3
EFFECTIVITY 24-22-00
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_A319/A320/A321 TECHNICAL TRAINING MANUAL
MECHANICS / ELECTRICS & AVIONICS COURSE 24 ELECTRICAL POWER
UF94200
EFFECTIVITY Page 146
ALL
AC GENERATION - GENERATOR CONTROL UNIT (GCU 1/2) D/O - CONTROL AND PROTECTION - ENGINE
FIRE AND OPEN FEEDER CABLE PROTECTION
TMUELAL01-P03 LEVEL 3
EFFECTIVITY 24-22-00
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_A319/A320/A321 TECHNICAL TRAINING MANUAL
MECHANICS / ELECTRICS & AVIONICS COURSE 24 ELECTRICAL POWER
UF94200
EFFECTIVITY Page 147
ALL
AC GENERATION - GENERATOR CONTROL UNIT (GCU 1/2) D/O
CONTROL AND PROTECTION - DIFFERENTIAL PROTECTION
The differential protection prevents the electrical
wiring between the two detection Current Transformers
from being damaged.
The protected area is divided into two parts (ZONE 1
& ZONE 2).
ZONE 1
The zone 1 protected area comprises the generator coils
and feeders between the IDG Current Transformer (CT)
and the GLC.
The zone 2 protected area comprises the wiring between
the GLC and the Current Transformer (CT).
In the event of a short circuit between phases or to
the ground, a noticeable difference between
transformer currents activates the protection system.
When activated the protection system opens GLC and BTC
(GEN FAULT light comes on) and the generator is still
excited.
If the fault persits, the Generator Control Relay is
tripped thus the generator is de-excited. The Bus Tie
Contactor closes automatically, therefore allowing the
network to be supplied by another generation source.
In that configuration, the short circuit is located
in zone 1.
When the generator is cut off, the protection system
of zone 2 remains operational.
The IDG senses a null current. If there is no short
circuit in zone 2, the sum of currents sensed by the
line CTs is null (opposite current direction).
If a short circuit occurs in zone 2, an unbalanced
current is detected by the GCU which activates the
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