Breaker Failure Protection Ccrbrf - ABB REC670 Applications Manual

Section 8
Current protection
8.9
194
Tau1Low: Multiplication factor to adjust the time constant Tau1 if the current is
lower than the set value ILowTau1. ILowTau1 is set in % of IBase1.
Tau2High: Multiplication factor to adjust the time constant Tau2 if the current is
higher than the set value IHighTau2. IHighTau2 is set in % of IBase2.
Tau2Low: Multiplication factor to adjust the time constant Tau2 if the current is
lower than the set value ILowTau2. ILowTau2 is set in % of IBase2.
The possibility to change time constant with the current value as the base can be
useful in different applications. Below some examples are given:
• In case a total interruption (low current) of the protected transformer all
cooling possibilities will be inactive. This can result in a changed value of the
time constant.
• If other components (motors) are included in the thermal protection, there is a
risk of overheating of that equipment in case of very high current. The thermal
time constant is often smaller for a motor than for the transformer.
ITrip: The steady state current that the transformer can withstand. The setting is
given in % of IBase1 or IBase2.
Alarm1: Heat content level for activation of the signal ALARM1. ALARM1 is set
in % of the trip heat content level.
Alarm2: Heat content level for activation of the output signal ALARM2. ALARM2
is set in % of the trip heat content level.
ResLo: Lockout release level of heat content to release the lockout signal. When
the thermal overload protection trips a lock-out signal is activated. This signal is
intended to block switching on of the protected circuit transformer as long as the
transformer temperature is high. The signal is released when the estimated heat
content is below the set value. This temperature value should be chosen below the
alarm temperature. ResLo is set in % of the trip heat content level.
ThetaInit: Heat content before activation of the function. This setting can be set a
little below the alarm level. If the transformer is loaded before the activation of the
protection function, its temperature can be higher than the ambient temperature.
The start point given in the setting will prevent risk of no trip at overtemperature
during the first moments after activation. ThetaInit: is set in % of the trip heat
content level.
Warning: If the calculated time to trip factor is below the setting Warning a
warning signal is activated. The setting is given in minutes.

Breaker failure protection CCRBRF

1MRK 511 401-UEN A
IP14514-1 v6
Bay control REC670 2.2 IEC
Application manual