Clearing Secondary Cable Faults can be Affected by Cable Temperature Rise

A very important aspect to be considered in the protection against secondary cable faults, by a transformer secondary breaker or internal fuse, is the rapid decay of fault-current magnitude as a function of cable resistance change with respect to time. This is particularly true where small AWG conductor, such as in service leads, is associated with large kVA size transformers. This paper intends to show that for such secondary systems, routine fault coordiantion may not be correct.