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UBase shall be entered as rated phase-to-phase voltage of the protected object in primary kV.
8.14.2.2
Application possibilities
GUID-5053F964-C2D6-4611-B5EF-AC3DB0889F51 v5
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.
8.14.2.3
Undervoltage seal-in
GUID-13BE02D3-1322-4075-859B-617CFF608657 v7
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
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-US
Figure 298: Undervoltage seal-in of current start
8.14.3
Setting guidelines
GUID-2AE85EC4-669E-47C0-ADD4-3DBA83581096 v3
GlobalBaseSel: Selects the global base value group used by the function to define (IBase),
(
UBase) and (SBase).
Section 8
1MRK 505 343-UEN B
Current protection
462
Application manual
Summary of Contents for Relion 670 series
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