PT open delta and Wye wirings 1

[Ali-rashid]

Hello all.
I have some issues with PT wirings. your help is appreciated in advance.
1- can Wye PT wiring (3 PTs) provide phase angle measurements?
2- the figure below shows the connection of a single PT to Schneider Vamp40 feeder protection relay. the manual says that with this configuration, all voltage functions such as:
27- undervoltage
59- overvoltage
32- reverse power protection
Are all these functions possible with this pt config?

 

[davidbeach]

27 and 59 can be performed on the L1-L2 voltage. Anything involving L3 or anything that shifts the L1 and L2 relative to ground without changing the phase-phase voltage will be missed. Assuming relatively well balanced currents and voltages the 32 function should work as well, but will probably have a wider dead band around zero.

 

[waross]

Should the primary voltages be unequal it is possible to have reverse power on only one phase. Such an event may be missed with this connection.
With four wire wye:delta transformer banks reverse power on only one phase is an known issue.

Bill
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"Why not the best?"
Jimmy Carter