ABB RELION REX640 Technical Manual page 379

1MRS759142 F
4.1.4.3 Functionality
The accidental energization protection function GAEPVOC for the synchronous
generator is an overcurrent protection function which is enabled only when the
generator is at a standstill or in turning gear. The function is used to protect the
generator rotor from damage due to rapid heating.
A number of field conditions, such as generator operating errors, breaker head
flashovers, control circuit malfunctions, false actuation of breaker, or a combination
of these can cause accidental energization of the generators. The generator under
this condition suddenly causes a relatively heavy load to the surrounding network,
which might lead to power balance instability.
Since the generator starts behaving as an asynchronous motor, this three-phase
current develops higher current in the rotor, which may thermally damage the
generator in a few seconds. A very high thermal stress in both the stator winding
and the rotor has been produced by this situation.
The prime mover can also suffer from mechanical damage in moving parts like
turbine blades or gearing teeth. Lack of oil may damage the bearings as lube pumps
are not in operation when the generator is at a standstill. The turning gear oil
pumps are not in operation either and the accidental energization may significantly
damage the turning gear.
4.1.4.4 Analog channel configuration
GAEPVOC has two analog group inputs which must be properly configured.
Table 424: Analog inputs
Input
I3P
U3P
There are a few special conditions which must be noted with the configuration.
Table 425: Special conditions
Condition
U3P connected real meas-
urements
Improper analog channel configuration causes a validation error if the analog
channels are not completely configured or they do not match with certain settings.
check the contents of this chapter and also the preprocessing blocks in this
document. The configuration can be written to the protection relay once the
mismatch is corrected.
REX640
Technical Manual
See the preprocessing function blocks in this document for the possible
signal sources.
Description
The function can work with any two voltage channels connec-
ted but it is recommended to connect all three voltage chan-
nels.
Description
Three-phase currents
Three-phase voltages
Protection functions
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