Wire Fault Diagnosis in the Frequency Domain by Impedance Spectroscopy

Abstract

The typical methods for the wire fault location are the time-domain reflectometry (TDR) and frequency-domain reflectometry (FDR). In TDR, attenuation and dispersion of the reflected signal limit the reachable accuracy for wire faults location. Because time of flight is evaluated, the wire faults with small impedance changes are difficult to locate. The FDR method has better accuracy than the TDR method, because power signals are used as incident signals and Fourier transform is applied to locate wire faults. However, it is difficult to identify the types of wire faults. A new technique is proposed to detect and locate the wire fault using impedance spectroscopy (IS). IS is applied to measure the input impedance of the wiring system. The load impedance of the wire fault can be abstracted from the input impedance in order to identify the type of wire faults. The input impedance is a period function of the frequency and the period of this function is linearly proportional to the distance to the fault. The fast Fourier transform of the input impedance can give a single spike to locate the wire fault. This novel method enables the location of hard (open and short circuits) and soft (wire faults with small impedance changes) faults. The input impedance of the wire faults in the defined low-frequency range can be applied to identify the types of wire faults. The capacitance and inductance of the cable system can be applied to detect the wire fault if it is open or short circuit. The measurement deviation of the wire fault location in this paper is maximal 40 cm and is independent of the distance to wire faults.