Base Quantities - ABB RELION 670 SERIES Applications Manual

Section 9
Current protection
9.13.2.1
9.13.2.2
562
fault affects a generator, the fault current amplitude is a function of time, and it depends
on generator characteristic (reactances and time constants), its load conditions
(immediately before the fault) and excitation system performance and characteristic. So
the fault current amplitude may decay with time. A voltage-restrained overcurrent relay
can be set in order to remain in the picked-up state in spite of the current decay, and
perform a backup trip in case of failure of the main protection.
The IED can be provided with a voltage-restrained time overcurrent protection
(VRPVOC, 51V). The VRPVOC (51V) function is always connected to three-phase
current and three-phase voltage input in the configuration tool, but it will always measure
the maximum phase current and the minimum phase-to-phase voltage.
VRPVOC (51V) function module has two independent protection each consisting of:
• One overcurrent step with the following built-in features:
• 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).

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.
Application possibilities
VRPVOC (51V) function can be used in one of the following applications:
1MRK 506 369-UUS -
Line distance protection REL670 2.2 ANSI
Application manual