ABB Relion 670 Series Applications Manual page 217

1MRK 511 401-UUS F
VRPVOC (51V) function module has two independent protection each consisting of:
• One overcurrent step with the following built-in features:
•
•
• One undervoltage step with the following built-in feature:
•
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).
8.16.2.1 Base quantities
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.
8.16.2.2 Application possibilities
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.
8.16.2.3 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(51V) function, the configuration is done according to figure 98. 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
Bay control REC670
Application manual
Selectable definite time delay or Inverse Time IDMT characteristic
Voltage restrained/controlled feature is available in order to modify the pick-up level of
the overcurrent stage in proportion to the magnitude of the measured voltage
Definite time delay
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Section 8
Current protection
GUID-08944177-73CF-4FB4-818E-3B7AC4F625EE v4
GUID-5053F964-C2D6-4611-B5EF-AC3DB0889F51 v5
GUID-13BE02D3-1322-4075-859B-617CFF608657 v7
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