Current Protection - ABB Relion 670 Series Product Manual

Busbar protection REB670
Version 2.2

6. Current protection

Directional phase overcurrent protection, four steps
OC4PTOC
Directional phase overcurrent protection, four steps
(OC4PTOC) has an inverse or definite time delay for each
step.
All IEC and ANSI inverse time characteristics are available
together with an optional user defined time characteristic.
The directional function needs voltage as it is voltage
polarized with memory. The function can be set to be
directional or non-directional independently for each of the
steps.
A second harmonic blocking level can be set for the function
and can be used to block each step individually.
This function can be used as a backup bay protection (e.g.
for transformers, reactors, shunt capacitors and tie-
breakers). A special application is to use this phase
overcurrent protection to detect short-circuits between the
feeder circuit breaker and feeder CT in a feeder bay when
the circuit breaker is open. This functionality is called end-
fault protection. In such case unnecessarily operation of the
busbar differential protection can be prevented and only fast
overcurrent trip signal can be sent to the remote line end. In
order to utilize this functionality the circuit breaker status
and CB closing command must be connected to the IED.
One of the overcurrent steps can be set and configured to
act as end-fault protection in the IED.
The function is normally used as end fault protection to
clear faults between current transformer and circuit breaker.
Four step single phase overcurrent protection
PH4SPTOC
Four step single phase, non-directional overcurrent
protection (PH4SPTOC) has an inverse or definite time
delay independent for each step separately.
All IEC and ANSI time delayed characteristics are available
together with an optional user defined time characteristic.
The function is normally used as end fault protection to
clear faults between current transformer and circuit breaker.
Directional residual overcurrent protection, four
steps EF4PTOC
Directional residual overcurrent protection, four steps
(EF4PTOC) can be used as main protection for phase-to-
earth faults. It can also be used to provide a system back-
up, for example, in the case of the primary protection being
out of service due to communication or voltage transformer
circuit failure.
32
EF4PTOC has an inverse or definite time delay independent
for each step.
All IEC and ANSI time-delayed characteristics are available
together with an optional user-defined characteristic.
M12846-3 v18
EF4PTOC can be set to be directional or non-directional
independently for each step.
IDir, UPol and IPol can be independently selected to be
either zero sequence or negative sequence.
A second harmonic blocking can be set individually for each
step.
The residual current can be calculated by summing the
three-phase currents or taking the input from the neutral CT.
EF4PTOC also provides very fast and reliable faulty phase
identification for phase selective tripping and subsequent
reclosing during earth fault.
SEMOD121002-4 v4
Four step directional negative phase sequence
overcurrent protection NS4PTOC
Four step directional negative phase sequence overcurrent
protection (NS4PTOC) has an inverse or definite time delay
independent for each step separately.
All IEC and ANSI time delayed characteristics are available
together with an optional user defined characteristic.
The directional function is voltage polarized.
NS4PTOC can be set directional or non-directional
independently for each of the steps.
NS4PTOC can be used as main protection for
unsymmetrical fault; phase-phase short circuits, phase-
phase-earth short circuits and single phase earth faults.
NS4PTOC can also be used to provide a system backup for
SEMOD127816-4 v8
example, in the case of the primary protection being out of
service due to communication or voltage transformer circuit
failure.
Thermal overload protection, two time constants
TRPTTR
If a power transformer reaches very high temperatures the
equipment might be damaged. The insulation within the
transformer will experience forced ageing. As a
consequence of this the risk of internal phase-to-phase or
phase-to-earth faults will increase.
M13667-3 v20
The thermal overload protection (TRPTTR) estimates the
internal heat content of the transformer (temperature)
continuously. This estimation is made by using a thermal
model of the transformer with two time constants, which is
based on current measurement.
Two warning levels are available. This enables actions in
the power system to be done before dangerous
© 2017 - 2021 Hitachi Power Grids. All rights reserved
1MRK 505 373-BEN P
GUID-485E9D36-0032-4559-9204-101539A32F47 v6
M13243-3 v12
Hitachi Power Grids