Detection of Incipient Faults in Distribution Cables Based on Mathematical Morphology

Incipient faults would repeatedly occur in underground cables when cable insulations or splices are damaged and would eventually develop into a permanent fault. Due to the short duration of incipient faults, the conventional protection relays cannot detect this type of faults. The objective of this paper is to develop a robust incipient fault detection algorithm by using phase current. Based on morphological gradient wavelet (MGW), the proposed algorithm is to detect the fault-induced or operation-induced transients, and therefore identify the incipient faults according to the unique characteristics. It can be applied to detect both sub-cycle and multi-cycle incipient faults. The performance of the proposed algorithm is evaluated using data collected from PSCAD/EMTDC. In addition, to verify the applicability of the proposed algorithm, other disturbances caused by permanent fault, capacitor bank switching, load change, etc, are studied as well.