The series is designed for use with combined transformers (American tank transformers) or outdoor oil-immersed power transformers operating at frequencies of 50 and 60Hz. It is compatible with maximum equipment voltages ranging from 12 to 40.5kV and rated currents of 63-250A. The device can be conveniently mounted on the transformer tank cover or box wall, and can be tapped and replaced while the transformer is de-energized.