Voltage Transformers are encased in a thermoplastic case with the core and windings encapsulated in resin. They are designed for line to line operation but may also be used in a line to neutral or line to ground configuration at 58% of rated voltage.

All transformers with rated voltages 346 Volts and below are ANSI C57.13 Group 1. All transformers rated for 480 and 600 Volt are Group 2.