Toshiba GRL150-100 Series Instruction Manual page 64

528 BI1-COM-T
1536
By PLC
529 BI2-COM-T
1537
By PLC
Figure 3.3.7.1 CB State Monitoring Scheme Logic
Normally open and normally closed contacts of the CB are connected to binary inputs BIm and
BIn respectively, and functions of BIm and BIn are assigned to "CB_N/O_CONT" and
"CB_N/C_CONT" by PLC.
Circuit Breaker Condition Monitoring
Periodic maintenance of CB is required for checking of the trip circuit, the operation mechanism
and the interrupting capability. Generally, maintenance is based on a time interval or a number of
fault current interruptions.
The following CB condition monitoring functions are provided to determine the time for
maintenance of CB:
• Trip is counted for maintenance of the trip circuit and CB operation mechanism. The trip
counter increments the number of tripping operations performed. An alarm is issued and
informs user of time for maintenance when the count exceeds a user-defined setting TCALM.
The trip count alarm can be enabled or disabled by setting the scheme switch [TCAEN].
• Sum of the broken current quantity ∑ I
CB. The ∑ I
y
counter increments the value of current to the power 'y', recorded at the time of
issue of the tripping signal, on a phase by phase basis. For oil circuit breakers, the dielectric
withstand of the oil generally decreases as a function of ∑ I
changes, etc., may be required. 'I' is the fault current broken by CB. 't' is the arcing time
within the interrupter tank and it cannot be determined accurately. Therefore, 'y' is normally
set to 2 to monitor the broken current squared. For other circuit breaker types, especially those
for HV systems, 'y' may be set lower, typically 1.0. An alarm is issued when the count for any
phase exceeds a user-defined setting ∑ I
by setting the scheme switch [ ∑ I
• Operating time monitoring is provided for CB mechanism maintenance. It checks CB
operating time and the need for mechanism maintenance is informed if the CB operation is
slow. The operating time monitor records the time between issuing the tripping signal and the
phase currents falling to zero. An alarm is issued when the operating time for any phase
exceeds a user-defined setting OPTALM. The operating time is set in relation to the specified
interrupting time of the CB. The operating time alarm can be enabled or disabled by setting the
scheme switch [OPTAEN].
The maintenance program should comply with the switchgear manufacturer's instructions.
The CB condition monitoring functions are triggered each time a trip is issued, and they can also
be triggered by an external device via binary inputs assigned to No.1588:EXT_TRIP-A,
No.1589:EXT_TRIP-B, No.1590:EXT_TRIP-C and No.1591:EXT_TRIP by PLC as shown in
Figure 3.3.7.2.
CB_N/O_CONT
=1
CB_N/C_CONT
[CBSMEN]
"ON"
+
y
is counted for monitoring the interrupting capability of
ALM. The ∑ I
y
y
AEN].
⎯
63
1
&
2
t, and maintenance such as oil
y
count alarm can be enabled or disabled
⎯
6 F 2 S 0 8 2 8
t 0
CBSV
5.0s