Short-circuit Protection Of Intercomponent Cables On 3 Phase, Alternating Current, Permissible Mining Equipment

Magnetic and thermal magnetic circuit breakers are used to provide short-circuit protection for intercomponent cables an permissible mining equipment. Limits are needed for the circuit breaker settings which will adequately protect intercomponent cables under a short-circuit fault condition. Calculations reveal that the maximum allowable settings for large ampacity power cables are limited by the minimum available short-circuit currents while the maximum settings for small control cables are limited by the amount of current the cable can withstand. When the available short-circuit current is greater than the current the cable can withstand, no circuit breaker setting is practical. The use of some small control cables with large trailing cables will be eliminated from future approvals due to large available short-circuit currents. Present approvals would not be affected. A computer program is available from the Approval and Certification Center to calculate circuit breaker settings.