Harmonic Analysis of High-Impedance Fault Experimental Current Waveforms Using Fast Fourier Transform
Keywords: High impedance faults, HIF experimental tests, HIF detection, Overhead distribution networks, Harmonic analysis, Fast Fourier Transform
AbstractHigh impedance faults (HIFs) detection in overhead distribution networks have been a major challenge for utility engineers for a long time. The current flowing to ground path is so low that conventional protection does not detect HIFs. The problem becomes more critical when HIFs occur in rural feeders with many single-wire earth return networks, since the neutral protection is usually set above the normal unbalance current of the circuit to avoid its undue actuation, limiting the sensitivity of this protection for single phase-to-ground faults. Methods based on harmonic content analysis for HIF detection stand out for their simplicity, practicality, and ease of implementation. However, so that such methods do not present reliability issues, the harmonic indices thresholds need to be well adjusted, reconciling dependability and security of the HIF detection function. This paper presents a study of the harmonic components presents in the HIF current waveforms, obtained through experimental tests in a 13,8 kV distribution network, using Fast Fourier Transform. The study analyzed the harmonic components of the current waveforms recorded on a SEL-751 relay in 74 FAI events.