What should I do if I have unusual voltage readings between “x” terminals and the ground before grounding the secondary side of my Square D Delta-Wye LV transformer?

Issue:
Unusual voltage readings between secondary “x” side of a Square D Delta-Wye LV transformer

Product Line:
Low Voltage Transformers, LV Transformers

Environment:
Three phase Delta-Wye LV Transformers

Cause:
Ungrounded secondaries coils might cause unusual readings between either x0, x1, x2, or x3 to ground. These voltages may also vary with transformer secondary loading.

Resolution:
The only way to obtain predictable voltage readings to ground in such situations would be to physically ground the x0 secondary terminal. Before doing this, the customer should check with the AHJ (Authority Having Jurisdiction) follow the proper guidance to grounding the secondary coil of the transformer per local codes. With this terminal grounded, the secondary coil windings have a hard-wired ohmic reference to ground, and such Stray Induced Voltages will not be present.

If there are considerable voltage readings between x0 and ground, then customer might consider using a temporal overcurrent protection device such as a fuse or a circuit breaker to ground the x0 terminal. Once the terminal is grounded and the overcurrent protection device has not tripped x0 terminal can be safety grounded.​​​​​

Released for:Schneider Electric South Africa