9328900990 Rev L BE1-951 Reporting and Alarm Functions 6-17
operations of # ID
interruptMAX
×=
Equation 6-2. Dmax Set by Number of Operations
The setting is in terms of primary amps (the relay multiplies by the CT ratio before doing calculations).
If the breaker monitoring mode is set to sum I2, the relay internally squares the setting that is entered for
D
MAX
. The relay sums the square of the currents that are interrupted and will set the breaker duty alarm
when the sum exceeds the square of the D
MAX
setting. The approach to set D
MAX
is to select the
maximum number of operations at some current level and enter a D
MAX
calculated by the equation:
⎟
⎠
⎞
⎜
⎝
⎛
×= operations of #
2
interrupt
ID
MAX
Equation 6-3. Dmax Set Using Square Root Factor
Again, the setting is in terms of primary amps. The 0.5 power (i.e., square root factor) shown above for
the D
MAX
setting is to compensate for the fact that the relay internally squares the D
MAX
that is entered.
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.
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