ABB RET670 Product Manual page 15

ABB
Transformer protection RET670 ANSI
Pre-configured
Product version: 1.2
Four step residual overcurrent protection, zero
sequence and negative sequence direction
EF4PTOC (51N_67N)
The four step residual overcurrent protection
EF4PTOC (51N/67N) 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.
EF4PTOC (51N/67N) can be set directional or non-
directional independently for each of the steps.
IDir, VPol and IPol can be independently selected to
be either zero sequence or negative sequence.
Second harmonic blocking can be set individually
for each step.
EF4PTOC (51N/67N) can be configured to measure
the residual current from the three-phase current
inputs or the current from a separate current input.
Four step negative sequence overcurrent
protection NS4PTOC (4612)
Four step negative sequence overcurrent protection
(NS4PTOC, (4612) ) 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 or dual
polarized.
NS4PTOC (4612) can be set directional or non-
directional independently for each of the steps.
Thermal overload protection, two time constant
TRPTTR (49)
If a power transformer or generator reaches very
high temperatures the equipment might be
damaged. The insulation within the transformer/
generator will have forced ageing. As a
consequence of this the risk of internal phase-to-
phase or phase-to-ground faults will increase. High
temperature will degrade the quality of the
transformer/generator insulation.
The thermal overload protection estimates the
internal heat content of the transformer/generator
(temperature) continuously. This estimation is made
by using a thermal model of the transformer/
generator with two time constants, which is based
on current measurement.
Two warning pickup levels are available. This
enables actions in the power system to be done
before dangerous temperatures are reached. If the
temperature continues to increase to the trip value,
the protection initiates a trip of the protected
transformer/generator.
Breaker failure protection CCRBRF (50BF)
Breaker failure protection (CCRBRF) ensures fast
back-up tripping of surrounding breakers in case
the own breaker fails to open. CCRBRF (50BF) can
be current based, contact based, or an adaptive
combination of these two conditions.
Current check with extremely short reset time is
used as check criterion to achieve high security
against unnecessary operation.
Contact check criteria can be used where the fault
current through the breaker is small.
CCRBRF (50BF) can be single- or three-phase
initiated to allow use with single pole tripping
applications. For the three-phase version of
CCRBRF (50BF) the current criteria can be set to
operate only if two out of four for example, two
phases or one phase plus the residual current
pickups. This gives a higher security to the back-up
trip command.
CCRBRF (50BF) function can be programmed to
give a single- or three-phase re-trip of the own
breaker to avoid unnecessary tripping of
surrounding breakers at an incorrect initiation due
to mistakes during testing.
Broken conductor check BRCPTOC (46)
The main purpose of the function Broken conductor
check (BRCPTOC, 46) is the detection of broken
conductors on protected power lines and cables
(series faults). Detection can be used to give alarm
only or trip the line breaker.
1MRK 504 118-BUS A
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