Rockwell Automation 865 Differential Protection Relay - Manual (Page 98)

4-6 Supporting
Functions
865-UM001A-EN-P – July 2009
Table 4.5 – Setting Parameters of CT, CT’ Supervisor – CTSV ( )
Parameter Value Unit Default Description
Imax> 0.0 … 10.0 xIn 2.0 Upper setting for CT supervisor
Imin< 0.0 … 10.0 xIn 0.2 Lower setting for CT supervisor
t> 0.02 … 600.0 s 0.10 Operation delay
CT on On; Off - On CT supervisor on event
CT off On; Off - On CT supervisor off event
Table 4.6 – Measured and Recorded Values of CT, CT’ Supervisor – CTSV ( )
Parameter Value Unit Description
ILmax A Maximum of phase currents Measured
value
ILmin A Minimum of phase currents
Display Imax>,
Imin<
A Setting values as primary
values
Date - Date of CT supervision alarm
Time - Time of CT supervision alarm
Imax A Maximum phase current
Recorded
values
Imin A Minimum phase current
The relay has a condition monitoring function that supervises the
wearing of the circuit-breaker. The condition monitoring can give
alarm for the need of CB maintenance well before the CB condition
is critical.
The CB wear function measures the breaking current of each CB
pole separately and then estimates the wearing of the CB accordingly
the permissible cycle diagram. The breaking current is registered
when the trip relay supervised by the circuit breaker failure
protection (CBFP) is activated. (See Chapter 2 for CBFP and the
setting parameter "CBrelay".)
Breaker Curve and its Approximation
The permissible cycle diagram is usually available in the
documentation of the CB manufacturer (Figure 4.1). The diagram
specifies the permissible number of cycles for every level of the
breaking current. This diagram relates to the parameter settings for
the breaker condition monitoring function with maximum eight
[current, cycles] points. See Table 4.7. If less than eight points
needed, the unused points are set to [I
BIG
, 1], where I
BIG
is more than
the maximum breaking capacity.
If the CB wearing characteristics or part of it is a straight line on a
log/log graph, the two end points are enough to define that part of the
characteristics. This is because the relay is using logarithmic
interpolation for any current values falling in between the given
current points 2...8.
Circuit Breaker
Condition Monitoring