Short-circuit protection of distribution networks by the use of limiters

A LARGE PERCENTAGE of secondary cable faults in distribution networks “burn clear” rapidly. In such cases, the short-circuit current to the fault has not persisted for a sufficiently long period of time to raise the temperature of the cable conductor on either side of the fault to a high enough temperature to fuse, or permanently damage adjacent cable insulation. However, not even the most optimistic treatises on “burnoff” have ever asserted that all secondary cable faults are of this accommodating type. Furthermore, the fault consists of an electric arc between a number of energized copper conductors confined in the small space of the duct, surrounded by masses of molten metal and with water frequently present. Under such a combination of conditions, who can contend that the fault can be depended upon to always clear in time to protect the insulation of cables supplying the fault current?