Double star connected capacitor battery protection - includes transformer with primary winding between star points and delivering control signal when current deviates

摘要

Simplified protection of power capacitor battery is ensured by a current transformer as an isolating unit operating with an overburden. This makes the manufacture of the transformer easier and at the same time improves the reproducibility of response since it operates with a single working point. The primary (11) of the current transformer (10) is connected between the star points of the two capacitor batteries fed from three-phase network. The secondary (12) feeds a resistor R1 shunted by a voltage dependent impedance (20) and a full-wave rectifier (13). Overload or short-circuit in the capacitors results in circulating current between the star points and through the primary (11). Then the output of the rectifier activates a relay (14) disconnecting the capacitors.