Example
In the example below, the Inrush Restraint multiplier (2) was applied to the trip setting (100 A) from when the current went from zero to non-zero. This could have been caused by the switchgear being closed and taking load or the switchgear could have been already closed and the load could have been caused by either an upstream or downstream device closing.
Figure 148
Inrush Restraint Time/Current
diagram
The Inrush Restraint Multiplier of 2 caused the trip setting to
go from 100 A to
200 A for the duration of the Inrush
Restraint Time setting (200 ms). This effectively masked the inrush
current which had returned to a steady state level before the Inrush
Restraint Time expired and the configured setting was restored.
In this case a pickup event would have been logged when the measured current exceeded the pickup threshold that is 100 A, but the protection timing would not have started.
If the measured current had been higher than the pickup threshold when the inrush restraint timer expired, the protection timing for that element would have started. If the current remained above the pickup threshold for the protection trip time the ACR would trip.