• Selectable definite time delay or Inverse Time IDMT characteristic
• Voltage restrained/controlled feature is available in order to modify the
start level of the overcurrent stage in proportion to the magnitude of the
measured voltage
• One undervoltage step with the following built-in feature:
• Definite time delay
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 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
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.
UBase 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 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
Section 9 1MRK 506 369-UEN B
Current protection
528 Line distance protection REL670 2.2 IEC
Application manual
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