5-224 L30 Line Current Differential System GE Multilin5.7 CONTROL ELEMENTS 5 SETTINGS5There is one breaker arcing current element available per CT bank, with a minimum of two elements. This element calcu-lates an estimate of the per-phase wear on the breaker contacts by measuring and integrating the current squared passingthrough the breaker contacts as an arc. These per-phase values are added to accumulated totals for each phase and com-pared to a programmed threshold value. When the threshold is exceeded in any phase, the relay can set an output operandto “1”. The accumulated value for each phase can be displayed as an actual value.The operation of the scheme is shown in the following logic diagram. The same output operand that is selected to operatethe output relay used to trip the breaker, indicating a tripping sequence has begun, is used to initiate this feature. A timedelay is introduced between initiation and the starting of integration to prevent integration of current flow through thebreaker before the contacts have parted. This interval includes the operating time of the output relay, any other auxiliaryrelays and the breaker mechanism. For maximum measurement accuracy, the interval between change-of-state of theoperand (from 0 to 1) and contact separation should be measured for the specific installation. Integration of the measuredcurrent continues for 100 ms, which is expected to include the total arcing period.The feature is programmed to perform fault duration calculations. Fault duration is defined as a time between operation ofthe disturbance detector occurring before initiation of this feature, and reset of an internal low-set overcurrent function. Cor-rection is implemented to account for a non-zero reset time of the overcurrent function.Breaker arcing currents and fault duration values are available under the ACTUAL VALUES RECORDS MAINTENANCE BREAKER 1(2) menus.• BKR 1 ARC AMP INT-A(C): Select the same output operands that are configured to operate the output relays used totrip the breaker. In three-pole tripping applications, the same operand should be configured to initiate arcing currentcalculations for poles A, B and C of the breaker. In single-pole tripping applications, per-pole tripping operands shouldbe configured to initiate the calculations for the poles that are actually tripped.• BKR 1 ARC AMP DELAY: This setting is used to program the delay interval between the time the tripping sequence isinitiated and the time the breaker contacts are expected to part, starting the integration of the measured current.• BKR 1 ARC AMP LIMIT: Selects the threshold value above which the output operand is set.Figure 5–104: ARCING CURRENT MEASUREMENTInitiateBreakerContactsPartArcExtinguished100 msProgrammableStart DelayStartIntegration StopIntegrationTotal Area =BreakerArcingCurrent(kA·cycle)
