The undervoltage function can be enabled or disabled. Sometimes in order to obtain the
desired application functionality it is necessary to provide interaction between the two
protection elements within the VRPVOC (51V) function by appropriate IED
configuration (for example, overcurrent protection with under
-voltage seal-in).
Sometimes in order to obtain the desired application functionality it is necessary to
provide interaction between the two protection elements within the D2PTOC(51V)
function by appropriate IED configuration (for example, overcurrent protection with
under-voltage seal-in).
9.14.2.1 Base quantities
GUID-08944177-73CF-4FB4-818E-3B7AC4F625EE v4
GlobalBaseSel defines the particular Global Base Values Group where the base
quantities of the function are set. In that Global Base Values Group:
IBase shall be entered as rated phase current of the protected object in primary
amperes.
VBase shall be entered as rated phase-to-phase voltage of the protected object in
primary kV.
9.14.2.2 Application possibilities
GUID-5053F964-C2D6-4611-B5EF-AC3DB0889F51 v5
VRPVOC (51V) 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
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.
1MRK 502 071-UUS A Section 9
Current protection
Generator protection REG670 2.2 ANSI and Injection equipment REX060, REX061, REX062 427
Application manual
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