Override; Zone Selective Interlocking (Zsi) - Eaton Power Xpert PXR Series Manual

3 Line protection setting description
Any of the configurable relay contacts can be used to remotely indicate when Maintenance
Mode is active. Auxiliary power (24 V DC) is required for the remote indication via a relay
contact.

3.7 Override

The PXR trip unit provides an override trip function that will trip the circuit breaker at the
withstand rating of the circuit breaker frame. This function is factory set and reacts to the
peak current level. It is always active regardless of the user's instantaneous adjustment
selection. The instantaneous ("INST") indicator shows this cause-of-trip.

3.8 Zone selective interlocking (ZSI)

The zone selective interlocking (ZSI) function is an option when ordering the circuit breaker.
ZSI functions in conjunction with the short delay and ground fault protection functions. ZSI
provides the fastest possible tripping for faults within the zone of protection of the circuit
breaker and also provides positive coordination among all circuit breakers in the system
(mains, ties, feeders, and downstream circuit breakers). Application note (AP02602002E) is
available and has additional detail.
When ZSI is enabled, a fault within the zone of protection will immediately trip the breaker
and send a signal to upstream trip units to restrain them from tripping immediately. The
restraining signal causes the upstream circuit breakers to follow their set coordination time
delays so that the service is interrupted to the isolated fault area only while the fault is
cleared in the shortest time possible.
The ZSI is wired using a set of three wires labeled zone in (Zin), zone out (Zout), and zone
common (Zcom). These signals are compatible will all Eaton circuit breakers which have
the ZSI function. The zone out signal is sent whenever a ground fault pickup or short delay
pickup is exceeded. This provides maximum selectivity for coordination with larger upstream
circuit breakers.
ZOUT
ZIN
ZCOM
breaker
ZOUT
ZIN
ZCOM
breaker
ZOUT ZOUT
ZIN ZIN
ZCOM ZCOM
breaker breaker
typical Zone Selective Interlock wiring
Motor protection circuit breakers are used in the final breaker (lowest zone) in a complete
ZSI enabled system. The zone out (Zout) signal is sent whenever a short circuit delay protec-
tion or ground fault protection pickup is exceeded. This indicates to the circuit breaker in
the zone above that the fault has been seen and will be acted upon. For all motor protection
circuit breakers, the zone in (Zin) signal is not used.
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PXR tRiP units foR PoweR Defense molDeD case ciRcuit bReakeRs MN012007EN March 2019 www.eaton.com
zone 1
ZOUT
ZIN
ZCOM
breaker
zone 2
ZOUT
ZIN
ZCOM
breaker
zone 3