GE Industrial Solutions Entellisys 5.0 User Manual - Manual (Page 140)

Multi-point functions 140
7
7.6 Ground Fault Tripping priority
The Ground Fault Tripping Priority (GFTP) function (optional) provides additional control to High
Resistance Systems with HRGF Location configured.
In High Resistance systems, a breaker may be faulted to ground but remain closed until
repaired. If another breaker faults to ground on another phase, an over current condition will
occur on both breakers and both breakers may trip on ground fault or over current - depending
on the settings. In this case however, the system need only trip one breaker.
This function prioritizes which circuit breaker is tripped first to clear over current condition
leaving one ground fault. This allows critical loads to be maintained.
Operation
The pickup of only the highest priority breaker in pickup will be delayed by 100ms. It does not
cascade the delays up the priority list.
GF Tripping Priority will update the time delay of a breaker that is in ground fault pickup and has
the highest priority assigned.
For systems with GF Tripping priority and GF ZSI are both used two functions interact as follows:
• GF Tripping Priority will update the time delay of a breaker if it is a member of a GF ZSI
zone
• ZSI will not update the delays of a breaker with a priority assigned.
Time delays are limited to 400ms maximum.
Delays in the I2t region are not modified.
Prerequisites
HRGF Detection must be optioned, see High Resistance Ground Fault Detection Relay
on page 89
MSGF must not be optioned, see Multi-Source Ground-Fault Relay on page 119
Switchable GF must be enabled and set at each breaker which will be assigned a tripping
priority, see
Ground Fault protection on page 65
ZSI must be optioned, see Zone Selective Interlock on page 129
Events
“GF Trip priority operated” – logged when a breaker either picks up or drops out of GF, GF
Tripping Priority operates to modify the delay values.