Disconnector device model ZU 4
Surge arresters for medium voltage systems are often equipped with a disconnector that permits the disconnection of the surge arrester in case of an internal fault. This disconnection prevents a persistent fault in the network and provides a visual indication that the surge arrester is defect. The disconnector is activated by an increase in internal pressure due to the electrical arc caused by the sublimation of the internal connecting wire as a result of the fault current. The operating mechanism is very reliable and the characteristc remains constant even over long time.
NOTE: It is important to ensure that sufficient insulating distance is kept for parts remaining energised after the detachment of the lower part of the disconnector.