GE Industrial Solutions Entellisys 5.0 User Manual - Manual (Page 65)

Overcurrent protection 65
5
5.1.2.5 Usage
ST Overcurrent Protection goes into pickup when the current in any phase is above the ST
pickup setting. ST pickup, trip, and dropout events are recorded in the Entellisys Sequence of
Events log. Waveforms and fault reports are also captured on a ST trip event, and can be viewed
from the Sequence of Events log.
The Entellisys system provides instantaneous overcurrent protection by tripping the circuit
breaker with no intentional delay when the sensed input current exceeds the programmed IOC
threshold. IOC trip events are recorded in the Entellisys Sequence of Events log. Waveforms and
fault reports are also captured on an IOC trip event, and can be viewed from the Sequence of
Events log.
5.1.3 Ground Fault protection
There are two levels of Ground Fault (GF) Overcurrent Protection available in the Entellisys
system. The first level is provided by the Entellisys CPU. This function is optional, and its
parameters, including whether to trip the circuit breaker or activate an alarm on a fault, are
user-programmable. The second level is provided by the individual Messenger. This function is
also optional, but its parameters are not user-programmable; the pickup and delay are set to
the maximum allowed for a given configuration. Also, the GF function performed at the
Messenger only trips the circuit breaker.
A GF alarm-only option is always available.
5.1.3.1 Ground Fault protection curves
There are seven GF delay bands available in Entellisys:
For 60 Hz systems
Band 1: 0.025 sec < T < 0.092 sec (see NOTE)
Band 2: 0.058 sec < T < 0.158 sec
Band 3: 0.100 sec < T < 0.200 sec
Band 4: 0.167 sec < T < 0.267 sec
Band 5: 0.217 sec < T < 0.317 sec
Band 6: 0.283 sec < T < 0.383 sec
Band 7: 0.400 sec < T < 0.500 sec.
For 50 Hz systems
Band 1: 0.030 sec < T < 0.095 sec (see NOTE)
Band 2: 0.060 sec < T < 0.160 sec
Band 3: 0.100 sec < T < 0.200 sec
Band 4: 0.170 sec < T < 0.270 sec
Band 5: 0.220 sec < T < 0.320 sec
Band 6: 0.280 sec < T < 0.380 sec
Band 7: 0.400 sec < T < 0.500 sec