Breaker Arcing Current - GE 845 Instruction Manual

CHAPTER 4: SETPOINTS

Breaker Arcing Current

845 TRANSFORMER PROTECTION SYSTEM – INSTRUCTION MANUAL
The 845 relay provides one Breaker Arcing Current element.This element calculates an
estimate of the per-phase wear on the breaker contacts by measuring and integrating the
current squared passing through the breaker contacts as an arc. These per-phase values
are added to accumulated totals for each phase and compared to a programmed
threshold value. When the threshold is exceeded in any phase, the relay can set an output
operand and set an alarm. The accumulated value for each phase can be displayed as an
actual value.
The same output operands that are selected to operate the Trip output relay that is used to
trip the breaker indicating a tripping sequence has begun, are used to initiate this feature.
A time delay is introduced between initiation and starting of integration to prevent
integration of current flow through the breaker before the contacts have parted. This
interval includes the operating time of the output relay, any other auxiliary relays and the
breaker mechanism. For maximum measurement accuracy, the interval between the
change-of-state of the operand (from 0 to 1) and contact separation should be measured
for the specific installation. Integration of the measured current continues for 100 ms,
which is expected to include the total arcing period.
Figure 4-113: Breaker Arcing Current Measurement
Path:
Setpoints > Monitoring > Breaker > BKR 1 Monitor > BKR 1 Arcing Current
FUNCTION
Range: Disabled, Alarm, Latched Alarm, Configurable
Default: Disabled
MONITORING
4–267