GE Industrial Solutions Entellisys 5.0 User Manual User Manual
Page 62
Single-point functions
62
5
Figure 5-2 Setting parameters of IOC/ST protection for Breaker 2
IOC Type
Standard IOC
The Messenger's digital IOC (Standard IOC) function will trip after 5 consecutive samples are
found to be above the pickup rating. This occurs within 1.3 milliseconds or within 1/10
th
of a
power cycle.
Adjustable Selective IOC (Waveform Recognition)
Instantaneous overcurrent has been expanded to provide waveform recognition further
improving selectivity to GE current limiting breakers downstream of the Entellisys switchgear.
Selective Discrimination will trip within the second 1/2 power cycle of fault current above the
pickup setting.
Downstream External ZSI Input
Entellisys is capable of accepting a ZSI signal from a downstream overcurrent device. If a
downstream device is detected, “Downstream ZSI Device” will read “Available.”
When a ZSI device is available then the messenger will respond to a restraint signal and will
restrain Short Time and IOC to the “IOC ZSI Restrain Time” and “ST Time Delay” settings.
Further more, the ZSI restraint signal will propagate to breakers up stream as defined by the
Entellisys ZSI Zone configuration. (
See section 7.5 Downstream Zone Selective Interlocking
for more details.
Curve I
2
T
The I
2
T option is available with each of the seven delay bands listed above. Note that the trip
times will not be shorter than the values listed above for the delay bands, even when the I
2
T
curve is selected. For example, suppose ST band 6 (60 Hz) is selected and I
2
T is enabled. On a