Basler Electric BE1-700 - Manual (Page 141)

Breaker Duty Monitoring (BE1-700C)
When the breaker opens, the N th power of 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 6-6 illustrates breaker status (SB-LOGIC) during a fault and protective trip.
Table 6-6 serves as a legend for the call-outs of Figure 6-6.
The relay sums the N th power of the currents that are interrupted and will set the breaker duty alarm when
the sum exceeds the N th power of the maximum breaker duty (D
max
) setting. The user must enter a value
for N and a value for D
max
.
To determine N and D
max
, the user needs to find two measurements of allowable breaker wear. These
levels would typically be the maximum number of operations at load level currents and the maximum
number of operations at maximum fault rating.
Point 1; # Ops @ I
max load
Point 2; # Ops @ I
max fault
To determine the breaker wear exponent N, using the above data points as an example, apply this
equation:












=
load max
fault max
fault max
load max
I
I
log
I @ Ops #
I @ Ops #
log
N
N can be any value from 1 to 3.
Using values for I
max load
and I
max fault
in primary amperes (the relay multiplies by the CTR before doing
calculations), the value for maximum breaker duty, D
max
, is calculated from either of these two equations:
( )
( )
N / 1
I @ Ops # I D
load max
N
load max max
• =
( )
( )
N / 1
I @ Ops # I D
load max
N
load max max
• =
Both of the last two equations should yield the same value for D
max
.
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 block 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.
9376700990 Rev M BE1-700 Reporting and Alarm Functions 6-9