GE Industrial Solutions Entellisys 5.0 User Manual - Manual (Page 153)

Administration 149
8
For all MSGF summation zones for both Alarm-Only & Trip Relays for Topology 0
NOTE: Although the Pickup is set to 30 Amps, Entellisys automatically enforces a “Zone
Minimum Pickup Setting” for Multi-Source Ground-Fault. The “Zone Minimum Pickup Setting” is
20% of the largest CT rating in the corresponding zone.
8.2.4 Ground Fault Trip Priority
By default, each breaker will be excluded from the High Resistance GF Trip Priority scheme while
operating with RELT (topology 0) settings.
8.2.5 RELT Settings for Zone Selective Interlock
A ZSI zone is made of one or more MSGF zones, main, tie, and feeder circuit breakers. A ZSI zone
can be either a ZSI-Short Time zone, ZSI-Ground Fault zone or both.
ZSI delays will be ignored by any breaker operating with RELT (Topology 0) settings. The delay will
propagate upstream preserving selectivity on all breakers that are NOT operating with RELT
(Topology 0) settings (see figure 8-7). Multi-point RELT effectively disables ZSI altogether. (see
Configuring ZSI parameters on page 131 )
Figure 8-7 ZSI Operation
In Figure 8-7, demonstrates the interaction between ZSI and RELT. In this case, the gear has both
buses fed from a single main and the user has placed the tie in RELT while they are working near
the feeder.
Setting Value
Pickup Setting 30 Amps
Time Delay BAND 1
Curve I 2 T DISABLED