Abb Research Ltd.

Jan Kuhlefelt

Ruzica Loitzl

Joachim Glatz Reichenbach

Zdenek Pelanek

Jo Slashedrgen Skindho Slashedj

Edgar Dullni

Ralph Strumpler

A power switching apparatus is disclosed which has an electrical conductor to which high voltage can be applied. A series of circuits formed by a switching point and a current-limiting element which contains PTC thermistors and varistors is arranged in the cable run of the electrical conductor. An apparatus for operating the switching point interacts with the current-limiting element. The current-limiting element has n (where n is a natural number greater than 1) series-connected parallel circuits each having at least one PTC thermistor and at least one varistor connected in parallel with it. A current sensor arranged in the cable run of the electrical conductor or those connections of one of the PTC thermistors and of the varistor connected in parallel with it which are interconnected at two junction points in one of the parallel circuits are operatively connected to the input of the operating apparatus. Such a power switching apparatus is designed using economic components, such as PTC thermistors and varistors for low-voltage applications, and a switching device which is designed for switching only low currents and can effectively limit large and small short-circuit currents without the current-limiting element connected upstream of the switching device, and/or the switching device, being overloaded.

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Skien, Norway

Jan Kuhlefelt