A thyristor circuit breaker for ship protection

A semiconductor short-circuit current limiting set (S-CLS) developed in Gdansk was designed for application in AC low voltage power systems with an insulated neutral point. This configuration is widely used for example on ships or coal mine electrical networks. This S-CLS is based on the Schulze-Buxloh system. The concept of the S-CLS set consists of a special connection of the neutral point of a generator or transformer. The neutral point contains a 3-phase rectifier or half controlled bridge, in which a current limiting thyristor circuit-breaker (TCB), with current commutation, shunts the DC side. In the case of a short-circuit in the circuits supplied by the generator or transformer, the TCB operates, disconnecting the DC branch of the neutral point. The operation is equivalent to interruption of the short-circuit current on the AC side. Tests were performed at the Electrotechnical Institute, the Gdansk Branch, on the S-CLS normal working conditions and during short-circuits. Some selected test results characterising the most important features of the S-CLS are discussed