Abstract
Accurate faulty phase detection under single-line-to-ground (SLG) fault is the basis of the emerging voltage-based fault arc suppression technology. Most conventional faulty phase recognition criteria assume the distributed line-to-ground parameters are symmetrical, therefore suffering invalidity in actual distribution networks especially under high-resistance ground-fault conditions. This paper firstly analyzes the magnitude and phase angle variation models of the phase-to-ground voltages before and after the SLG fault. Considering the asymmetrical distributed parameters and the line impedance, the specific phase-to-ground voltage variation rules corresponding to SLG fault on each phase are then discussed. Based on the voltage variation rules, a robust and practical method for faulty phase identification is proposed, which does not need the distributed parameters. Finally, the correctness of the variation rules and the availability of the proposed method is verified by simulation. Comparative study shows the proposed method has better accuracy and applicability with the conventional methods when the asymmetry and ground-fault resistance are high.
Highlights
P OWER system reliability is critical to medium-voltage (MV) distribution networks [1], [2]
The ground fault transfer device based on low magnetizing inductance Transformer (JDBH [25], in China) cannot guarantee accurate SLG faulty phase identification on high-resistance ground fault condition
Based on the voltage variation rules, a practical faulty phase identification method is proposed using the variation of phaseto-ground voltages magnitude and phase angle after and before the SLG fault
Summary
P OWER system reliability is critical to medium-voltage (MV) distribution networks [1], [2]. The Ground Fault Neutralizer (GFN [24] in Sweden) uses the detected distributed parameters to recognize the faulty phase This method is difficult to adapt to the changing configuration of distribution lines. The ground fault transfer device based on low magnetizing inductance Transformer (JDBH [25], in China) cannot guarantee accurate SLG faulty phase identification on high-resistance ground fault condition. Based on the voltage variation rules, a practical faulty phase identification method is proposed using the variation of phaseto-ground voltages magnitude and phase angle after and before the SLG fault. The method for both over-compensated and under-compensated grounding conditions is separately presented. Comparative study with two conventional methods shows that the proposed method has better accuracy and applicability when the asymmetry and ground-fault resistance are high
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