Rockwell Automation 865 Differential Protection Relay - Manual (Page 70)

3-26 Protection
Functions
865-UM001A-EN-P – July 2009
Table 3.14 – Parameters of the Thermal Overload Stage T> (49)
Parameter Value Unit Description Note
Status -
Blocked
Start
Trip
Current status of the stage
F
F
Time hh:mm:ss Estimated time to trip
SCntr Cumulative start counter C
TCntr Cumulative trip counter C
Force Off
On
Force flag for status forcing for test
purposes. This is a common flag for
all stages and output relays, too.
Automatically reset by a 5-minute
timeout. Set
T % Calculated temperature rise. Trip
limit is 100 %. F
MaxRMS Arms Measured current. Highest of the
three phases.
Imax A kxIgn. Current corresponding to the
100 % temperature rise.
k> xIn Allowed overload (service factor) Set
Alarm % Alarm level Set
tau min Thermal time constant Set
ctau xtau Coefficient for cooling time constant.
Default = 1.0 Set
kTamb xIn Ambient temperature corrected max.
allowed continuous current
Imax40 %In Allowed load at Tamb +40
°C.
Default = 100 %.
Set
Imax70 %In Allowed load at Tamb +70
°C. Set
Tamb °C Ambient temperature. Editable
Samb=n/a. Default = +40
°C
Set
Samb
n/a
ExtAI1...16
Sensor for ambient temperature
No sensor in use for Tamb
External Analogue input 1...16
Set
For details of setting ranges see “Protection Stages” in Chapter 10.
Set = An editable parameter (password needed)
C = Can be cleared to zero
F = Editable when force flag is on
The circuit breaker failure protection can be used to trip any upstream
circuit breaker (CB), if the fault has not disappeared within a given
time after the initial trip command. A different output contact of the
relay must be used for this backup trip.
The operation of the circuit-breaker failure protection (CBFP) is
based on the supervision of the signal to the selected trip relay and
the time the fault remains on after the trip command.
Circuit-breaker failure
protection CBFP (50BF)