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ABB
Transformer protection RET650
Product version: 1.1
CCRBRF can be current based, contact based,
or an adaptive combination of these two
principles.
A current check with extremely short reset
time is used as check criterion to achieve a
high security against unnecessary operation.
A contact check criteria can be used where
the fault current through the breaker is small.
Breaker failure protection (CCRBRF) current
criteria can be fulfilled by one or two phase
currents, or one phase current plus residual
current. When those currents exceed the user
defined settings, the function is activated.
These conditions increase the security of the
back-up trip command.
CCRBRF function can be programmed to give
a three-phase re-trip of the own breaker to
avoid unnecessary tripping of surrounding
breakers at an incorrect initiation due to
mistakes during testing.
Pole discordance protection
CCRPLD
Circuit breakers and disconnectors can end
up with the poles in different positions (close-
open), due to electrical or mechanical
failures. This can cause negative and zero
sequence currents which cause thermal stress
on rotating machines and can cause
unwanted operation of zero sequence or
negative sequence current functions.
Normally the own breaker is tripped to
correct such a situation. If the situation
persists the surrounding breakers should be
tripped to clear the unsymmetrical load
situation.
The pole discordance function operates based
on information from the circuit breaker logic
with additional criteria from unsymmetrical
phase currents when required.
Directional over/underpower
protection GOPPDOP/GUPPDUP
The directional over-/under-power protection
GOPPDOP/GUPPDUP can be used wherever
a high/low active, reactive or apparent power
protection or alarming is required. The
1MRK 504 127-BEN -
Issued: February 2011
functions can alternatively be used to check
the direction of active or reactive power flow
in the power system. There are a number of
applications where such functionality is
needed. Some of them are:
• detection of reversed active power flow
• detection of high reactive power flow
Each function has two steps with definite
time delay. Reset times for both steps can be
set as well.
Negative sequence based
overcurrent function DNSPTOC
Negative sequence based overcurrent
function (DNSPTOC) is typically used as
sensitive earth-fault protection of power
lines, where incorrect zero sequence
polarization may result from mutual
induction between two or more parallel lines.
Additionally, it is applied in applications on
underground cables, where zero sequence
impedance depends on the fault current
return paths, but the cable negative sequence
impedance is practically constant.
The directional function is current and
voltage polarized. The function can be set to
forward, reverse or non-directional
independently for each step.
DNSPTOC protects against all unbalanced
faults including phase-to-phase faults. The
minimum start current of the function must
be set to above the normal system unbalance
level in order to avoid unintentional
functioning.
6. Voltage protection
Two step undervoltage protection
UV2PTUV
Undervoltages can occur in the power system
during faults or abnormal conditions. Two
step undervoltage protection (UV2PTUV)
function can be used to open circuit breakers
to prepare for system restoration at power
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