Three=phase transformer undervoltage currents acquisition unit - has current transformer in series with first winding of star selectively connected in series or parallel with second winding

摘要

Underground mining fire damp-proof three-phase transformer with two undervoltage windings per phase is fitted with a unit for acquiring the component currents on the undervoltage side of the system, and is designed to provide reliable overload protection for the transformer independent of the operational mode and power distribution being used. A current transformer is connected in series with each first winding in the star-connection system, the first winding(s) being arranged in the terminal box(es) for selective connection in series or parallel with the second winding of the system. Overcurrent release facilities are connected to the series transformer(s), and the release switch(es) are arranged in the tripping or control current loop of a power switch connected in front of the transformer or of a protection switch connected behind the transformer.