Winding Inter-Turn Fault Detection in a Silicon Steel Laminated Core Inductor using Sweep Frequency Response Analysis

This paper presents an offline fault detection technique; sweep frequency response analysis (SFRA) which is carried out by implementing the impedance response method to detect an inter-turn winding fault in a silicon steel laminated core inductor (LACOIN). The proposed technique is based on the fundamental components of the winding's physical geometry which consists of the winding resistance (R), inductance (L), and capacitance (C). A comparative study of the equivalent winding resistance, reactance, and impedance under the healthy and winding inter-turn fault conditions is carried out using Dowell's equation. The equation considers both the skin and proximity effects which causes winding parasitic parameters (resistance and inductance) to increase with the operating frequency. The analytical winding parameters were validated experimentally for the healthy, 1%, 3%, and 6% inter-turn short-circuit fault conditions of the LACOIN's winding. The methodology requires a low frequency bandwidth (DC - 100 kHz) and a simple signal processing technique, i.e., Fast Fourier transform (FFT) to determine the impedance frequency response from the measured voltage and current signals. This also enable us to detect as low as 1% inter-turn short-circuit fault out of 350 turns in the windings of the LACOIN. The results show that, inter-turn faults mostly affect the inductive and capacitive region of the impedance response plot which reduces the impedance magnitude's peak and increases the resonant frequency, hence using impedance peak and resonance frequency as indicators.