Development of a DC Current Limiting Interrupting System for Mines

摘要

A switching system for high fault current, 300- and 600-volt dc trolley and haulage systems, as used in the mining industry are presented. The system consists of paralleled main and auxiliary contactor circuits with a liquid metal current limiting device (CLD) in series with the auxiliary contactor. Upon detection of a fault, the current is commutated into the CLD circuit. The liquid metal vaporizes, increasing the CLD resistance and considerably decreasing the actucal current to be interrupted. This system will materially reduce the wear and tear on contactors because of the reduced interrupting requirement. The CLD is pressurized; when the current is interrupted liquid metal flows back into the bore, thus it is resetting. Electrical and mechanical design principles, that were found satisfactory in field tests, are presented as well as materials for use.