Application Possibilities - ABB REC670 Applications Manual

1MRK 511 401-UEN A
8.16.2.2
8.16.2.3
Bay control REC670 2.2 IEC
Application manual
UBase shall be entered as rated phase-to-phase voltage of the protected object in
primary kV.

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.
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 94.
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.
OR
OR
IEC12000183 V1 EN-US
Figure 94: Undervoltage seal-in of current start
VRPVOC
I3P*
U3P*
BLOCK
BLKOC START
BLKUV
Section 8
Current protection
GUID-5053F964-C2D6-4611-B5EF-AC3DB0889F51 v5
GUID-13BE02D3-1322-4075-859B-617CFF608657 v7
Trip output
TRIP
TROC
t
TRUV
STOC
STUV
IEC12000183-1-en.vsd
223