Ground Differential Protection and Auto-transformer CT

[jvamos]

I would like to use an auto-transformer auxiliary CT with electromechanical relays for ground differential protection on a delta-wye resistor grounded transformer. The CT on the neutral is 200/5 and 2000/5 on the low side of the transformer. I need 10:1 ratio on the auto-transformer. I am having trouble in locating someone who makes the auto-transfomer type CT. Any help would be greatly appreciated.

 

[dpc]

Why do you want an auto-transformer type CT? Wouldn't a two-winding aux CT work?

 

[jvamos]

Because of possible Aux CT saturation and the high burden placed on the CTs by the electromechanical relays.