On-line identification of incipient flaws in underground cables using single-end sheath currents

Underground cable problems would occur frequently until they developed into permanent defects. The detection of incipient faults may help assess the condition of cable insulation and give an early warning before subterranean wires break down. In the modal domain, the properties of incipient fault traveling waves are investigated, and theoretical analysis reveals that the sum of sheath currents may be utilized to identify incipient faults. To identify an incipient defect, both the over-current and the wavelet transform modulus maximum of the sum of single-end sheath currents are evaluated. The defective phase is chosen based on the root-mean-squares of three phases once an incipient problem is identified. PSCAD/EMTDC is used to create a cable system model and simulation results indicate that the detection method can correctly identify incipient faults in a variety of fault situations.