Transformer phase shifts 1

[lkincer]

For delta-wye 161-13 kV transformer, I'm not seeing a 30 degree shift between primary and secondary currents. In fact the secondary currents are LEADING the primary by 120 degrees. This is being seen on a SEL 787 relay. At this point the transformer is lightly loaded. Is this correct?

 

[davidbeach]

In the default ANSI world, no it is not correct. No idea where you are, no idea what your specific application is. Who knows?

 

[waross]

Your relay may be looking at phase to phase load current on the delta and phase to neutral load current on another phase of the wye.


Bill
--------------------
"Why not the best?"
Jimmy Carter

 

[stevenal]

Your 787 may have replaced individual single phase relays. When applied to a delta-wye, the CT secondaries would need to be wired wye-delta to undo the phase shift and filter out the zero sequence current. If applied to the existing system without modifying the CT wiring, your 787 should see 0 degrees shift. The 120 degree shift indicates incorrect phase to relay input wiring. With some tweaking of the W1CT, W2CT, W1CTC and W2CTC settings, the relay may be able to compensate for the mis-wiring and still show zero operate current for load and through fault current.

 

[DTR2011]

I believe the ACCSELerator SW contains a commissioning tool that will help you sort things out. It should be supplied with the relay, or can be downloaded from the website.