ABB Relion REG670, Applications Manual

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UBase shall be entered as rated phase-to-phase voltage of the protected object in
primary kV.
9.14.2.2 Application possibilities
VRPVOC function can be used in one of the following applications:
• voltage controlled over-current
• voltage restrained over-current
In both applications a seal-in of the overcurrent function at under-voltage can be
included by configuration.
9.14.2.3 Undervoltage seal-in
In the case of a generator with a static excitation system, which receives its power from
the generator terminals, the magnitude of a sustained phase short-circuit current
depends on the generator terminal voltage. In case of a nearby multi-phase fault, the
generator terminal voltage may drop to quite low level, for example, less than 25%,
and the generator fault current may consequently fall below the pickup level of the
overcurrent protection. The short-circuit current may drop below the generator rated
current after 0.5...1 s. Also, for generators with an excitation system not fed from the
generator terminals, a fault can occur when the automatic voltage regulator is out of
service. In such cases, to ensure tripping under such conditions, overcurrent protection
with undervoltage seal-in can be used.
To apply the VRPVOC function, the configuration is done according to figure 203 . As
seen in the figure, the pickup of the overcurrent stage will enable the undervoltage
stage. Once enabled, the undervoltage stage will start a timer, which causes function
tripping, if the voltage does not recover above the set value. To ensure a proper reset,
the function is blocked two seconds after the trip signal is issued.
Trip output
OR
OR
t
IEC12000183-1-en.vsd
VRPVOC
I3P*
U3P*
BLOCK
BLKOC
BLKUV
TRIP
TROC
TRUV
START
STOC
STUV
IEC12000183 V1 EN
Figure 203: Undervoltage seal-in of current start
Section 9
1MRK 502 071-UEN -
Current protection
396 Generator protection REG670 2.2 IEC and Injection equipment REX060, REX061, REX062
Application manual