Cable temperature requirements and fault current detection in telephone equipment locations

The problem of the inability of overcurrent protection devices to operate consistently in telephone switching equipment locations is addressed. Overcurrent protection (fuses or circuit breakers) will not always function with DC power to ground faults in the major power feeders because of the design philosophies of the power feeders and their associated overcurrent protection devices. Sizing principles of the power feeders from the battery plant to the secondary DC power distribution are listed, and the issues of cable temperatures and fault current detection are discussed. Fault current monitor considerations, including the description of microprocessor-controlled power monitor and control systems (MPMCs) are presented.<>