Protection device for transformer outputs in the medium-voltage range

摘要

The aim is to provide transformer protection which is intended to improve the American usages of transformer protection having power fuses. In order to be able to cut off any current which may arise in a transformer output, it is proposed to combine a switching apparatus (1) with a current-limiting fuse (2) in order to achieve effective short-circuit protection. A time-delay element (6) which is connected to a trip element (7) is driven by means of a low-voltage wrap-around converter (5), in order to provide excess-current protection. The trip element (7) operates on a mechanical drive (8) which is connected to the switching apparatus (1). A bimetallic relay (12) can also be used instead of the time-delay element (6), the make contact (13) of which bimetallic relay (12) connects a trip element (14) in parallel with two phases of said bimetallic relay (12). In consequence, a mechanical drive (15) is tripped. Both trip elements (7, 14) are trip devices of an earth-leakage current protection circuit breaker trip mechanism. <IMAGE>