Third Harmonic Current Phase Angle Behaviour During Branch Touching Wire Earth Faults

• Published in: IEEE transactions on power delivery 2024-11, p.1-10
• Main Authors: Ozansoy, C., Faulkner, M.
• Format: Article
• Language: English
• Subjects: Computational modeling; Current measurement; Electric potential; Harmonic analysis; High impedance fault; phase angle; phasor relationship; Power harmonic filters; Recording; Resistors; third harmonic current; Vegetation; Vegetation mapping; voltage reference; Wire
• ISSN: 0885-8977
• DOI: 10.1109/TPWRD.2024.3506940

This research scrutinizes credibility of the third harmonic (I 3h ) current phasor relationship with respect to the fundamental voltage (V 50-Hz ) as a potential signature of Vegetation High Impedance Faults (VeHIFs) using data from continuous-contact 'branch touching wire' earth faults. Prior work argued on a distinct phasor relationship between I 3h and V 50-Hz . Common HIF models simulate this distinct phase relationship as ∼ 180° with near perfect stability after only few cycles. This work uses a dataset of 132 phase-to-earth (ph-to-e) VeHIF test recordings to analyse temporal variations in the I 3h phase shift. The over-fault mean was ∼ 170° with a volatility (standard deviation (STD)) of 7°. Ninety-five percent of tests stabilised to these values within 1.25-s of fault inception. Outlier cases with long phase-shift stabilisation periods may pose a risk in the timely detection of earth faults. However, such cases were usually associated with low initial fault currents (I f ) for extended periods and were unlikely to cause ignition. Fault currents above 33mA are shown to have stable phase-shifts. Finally, a regressive statistical model is presented for modelling time sequences of I 3h phase-shift with respect to V 50-Hz .