IL17569
Page 8-8
Effective June, 2001
Figure 8-10. Zone Interlocking Example with FP-5000 and DT-3000
In general, if the Zone Interlocking Input is enabled, the absence of
a zone-in signal active, and an IOC or TOC pickup occurs, an
immediate trip will occur. The immediate trip has a 3-cycle pickup
delay to make sure the downstream devices have a chance to
activate the zone interlock signal. If the zone-in signal is active, then
the programmed delay time is used.
If the Zone In setpoint is set to “Phase” then any phase current
above of the IOC pickup or 1.5 times the TOC pickup will cause an
immediate trip in the absence of an active zone-in signal. Ground or
residual current IOC or TOC will not cause an immediate trip. The
1.5 time multiplier is used so that a low level current overload does
not cause an immediate trip. If the zone-in signal is active then the
programmed delay time is used.
If the Zone In setpoint is set to “Ground” then any ground or residual
current above the IOC pickup or the TOC pickup will cause an
immediate trip in the absence of an active zone-in signal. Phase
current IOC or TOC will not cause an immediate trip. If the zone-in
signal is active then the programmed delay time is used.
In the case that the breaker that is taking action fails to open the
circuit, the zone-out signal is removed in one of two ways:
1. If the breaker fail function is active then the zone out signal is
immediately removed. See Section 5 Programming on page 5-1
and Section 8.9 Breaker-Oriented Functions.
2. If the protective relay has operated but the current is still sensed,
the zone-out signal is removed 10 cycles after the operation.
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