BE1-951
Reporting and Alarm Functions
6-13
The breaker operations counter can be monitored to give an alarm when the value exceeds a threshold. See
Breaker Alarms in this section for more information about this feature.
Breaker operations can also be read using the RB command. The RB command returns the number of
breaker operations and breaker contact duty information.
RB Command
Purpose:
Read breaker status.
Syntax:
RB
Comments: No password access is required to read settings.
RB Command Example
1.
Use the RB command to obtain breaker information.
>RB
RB-DUTYA=92.04; RB-DUTYB=22.25; RB-DUTYC=27.87
RB-OPCNTR=65
Breaker duty monitoring is discussed in the following paragraphs.
Breaker Duty Monitoring
When the breaker opens, the current interrupted in each pole of the circuit breaker is accumulated by the
breaker duty monitor. Breaker opening is defined by the breaker status monitoring function (SB-LOGIC).
Figure 6-1 illustrates breaker status (SB-LOGIC) during a fault and protective trip. Table 6-7 serves as a
legend for the call-outs of Figure 6-1.
Each time the breaker trips, the breaker duty monitor updates two sets of registers for each pole of the
breaker. In the Accumulated
I
Duty registers, the breaker duty monitor adds the measured current in primary
amperes. In the Accumulated
I
2
Duty registers, the function adds the measured current squared in primary
amperes. The user selects which of the two sets of duty registers are reported and monitored when setting
up the breaker duty monitor.
Even though duty register values are calculated and stored in primary amperes or primary amperes-squared,
the duty value is reported as a percent of maximum. The user sets the value that the relay will use for 100
percent duty (DMAX). The value set for maximum duty is used directly for reporting the accumulated
I
Duty.
The square of the value set for maximum duty is used for reporting the accumulated
I
2
Duty.
Since the true measure of contact wear includes a factor for arcing time (t), an assumed arcing time for the
breaker should be included when choosing the setting for 100 percent interruption duty (DMAX).
When testing the relay by injecting currents into the relay, the values in the duty registers should be read
and recorded prior to the start of testing. Once testing is complete and the relay is returned to service, the
registers should be reset to the original pre-test values. A block accumulation logic input may be used when
testing so that simulated breaker duty is not added to the duty registers. The BLKBKR logic function is an
OR logic term (e.g., IN1 or VO7) which blocks the breaker monitoring logic when TRUE (1). BLKBKR is set
to zero to disable blocking. When breaker monitoring is blocked (logic expression equals 1), breaker duty
is not accumulated
