
Thermal overload protection, two
time constant TRPTTR
If the temperature of a power transformer/
generator reaches very high values 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-
earth faults will increase. High temperature
will degrade the quality of the transformer/
generator oil.
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 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 trip of the protected transformer/
generator.
Breaker failure protection CCRBRF
Breaker failure protection (CCRBRF) function
ensures fast back-up tripping of surrounding
breakers in case of own breaker failure to
open. CCRBRF can be current based, contact
based, or adaptive combination between
these two principles.
A current check with extremely short reset
time is used as a check criteria 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) function
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 or disconnectors can due to
electrical or mechanical failures end up with
the different poles in different positions (close-
open). This can cause negative and zero
sequence currents which gives 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 breaker 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 current 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 functions can alternatively be
used to check the direction of active or
reactive power flow in the power system.
There are 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 every step can be
set as well.
Negative sequence based
overcurrent function DNSPTOC
Negative sequence based overcurrent
function (DNSPTOC) is typically used as
Transformer protection 1MRK 504 110-BEN -
RET650
Product version: 1.0 Issued: September 2009
14 ABB