GE Industrial Solutions Entellisys System User Manual - Manual (Page 103)

Zone Selective Interlock 103
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7.4 Zone Selective Interlock
Entellisys provides support for Zone Selective Interlock (also referred to as ZSI). ZSI enables
selectivity of the power system within a zone. Entellisys can support up to four ZSI zones and is
able to dynamically respond to topology changes. Successful completion of ZSI setup requires
knowledge of power protection field concepts. The essential concepts are described in sections
that follow.
7.4.1 Zones
Entellisys can support up to four zones. Zones divide the topology of the system and group
topology circuit breakers with single power source with feeder and sub-feeder circuit breakers.
Topology circuit breakers are circuit breakers that control the source from which a load is
powered.
7.4.2 ZSI zones
ZSI zones are a subset of topology zones. Each ZSI zone can be a subset of one topology zone.
Hence the total number of ZSI zones is four. Each of the ZSI zones can support up to 30 circuit
breakers with Ground Fault (GF), four Multi-Source Ground-Fault (MSGF) groups, and 30 circuit
breakers with Short Time (ST) protection. Any of the circuit breakers may support both of the
protection types. However, in this case ZSI treats such a circuit breaker, as if it were two
separate circuit breakers.
Zones can be defined as independent or interdependent. Independent zones are ones where
there are no common circuit breakers for the selected operation mode, while interdependent
zones occur when two zones share at least one circuit breaker for a selected operation mode.
For more information on Multi-Source Ground-Fault relay and protection offered by them, see
Multi-Source Ground-Fault Relay on page 93 .
7.4.3 Protection types
ZSI operation can be configured to perform one of three protection types: ground fault
protection, short time protection, and ground fault and short time protection.
Ground fault protection includes multi-source ground-fault groups. Once a protection type is
selected, it applies to all ZSI zones. Also, if a ZSI zone is configured with circuit breakers
supporting ST and GF type protection and only GF protection is enabled, ZSI does not analyze
data from and takes no actions to perform ST protection. The same rule applies in the opposite
case.