ABB RELION RET670, Applications Manual

Page: 613 / 1016

• 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
• 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 (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).
9.17.2.1 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.
9.17.2.2 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.
9.17.2.3 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%,
1MRK 504 163-UUS A
Section 9
Current protection
Transformer protection RET670 2.2 ANSI 607
Application manual