ETAP - Protection Time-Current Curves - Current offset error

[EddyWirbelstrom]

When I assign a fuse or relay from the ETAP library to the one-line diagram symbol of an existing ETAP model, ETAP plots the time-current curve offset to the right by a current factor of 1.17.
When I assign the same fuse or relay from the ETAP library to the one-line diagram in a new ETAP model, ETAP correctly plots the time-current curve without the current offset.

Have any ETAP users encountered this problem, and how is it resolved ?

 

[dpc]

I suspect there is an option set on the existing model to offset the curve to account for the difference in fault current seen in the phase overcurrent devices when there is a phase-phase fault on the wye side of a delta-wye transformer. It is necessary to shift either the low side curve or the high curve to check selectivity for these faults.

I don't know much about ETAP, but the 1.17 is suspiciously close to the actual factor of 1.15 to make me think it is probably related to this.

 

[EddyWirbelstrom]

Thanks dpc, the sqrt(3) / 2 pri/sec current ratio for a PP fault on the secondary of a delta/star transformer is accomodated in ETAP by the user applying a "shift factor" in "plot options".
However the "shift factor" is set to 1.00
I have found that by deleting the fuse or relay and re-assigning the identical fuse or relay, the software plots correctly without the shift. This not a satisfactory solution.