Fault location for balanced pair cable by input-admittance measurement

Abstract

This paper proposes a method to detect a fault location in a faulty paired cable consisting of branching cables and different gauge wires along a length. Calculating an input-admittance of a faulty pair cable involves consideration of cable length, cable secondary constants, branching conditions, and a fault location. Under this principle, a measured input-admittance can be indicated by fault location if cable length, cable secondary constants, and branching conditions are known. In addition, when a calculated input-admittance agrees with a measured input-admittance, the fault can be located. However, a location error appears because actual cable secondary constants are slightly different from those cable secondary constants that, are calculated. This paper also describes the location errors caused by secondary constants differences. Furthermore, two improvement methods for location errors have been developed. One method applies the difference between input-admittances before and after fault. The other method refers a measured input-admittance of a fault-free cable to that of a faulty cable. As results, fault location errors in an open fault (a breakdown of wires) and an insulation degradation fault were significantly decreased.