Experimental and simulation study on current shock towards PT caused by switch type arc extinguishing

With spreading using of switch type arc extinguishing in 10 kV distribution network, it is necessary to study the over-current on traditional PT (potential transformer) during arc extinguishing. Firstly, the mechanism of Ferroresonance and low frequency oscillation, which is motivated by single-phase grounding and disappear during arc extinguishing, is theoretically introduced; secondly, a test platform of 10 kV ungrounded system is established, and series of single-phase grounding and disappear experiment are carried on under different capacitance current and PT; the last, comparing the traditional simulation results with experiment, a calculation method which takes characteristic of the core at deep saturation into consideration is proposed. Research results show that Ferroresonance and low frequency oscillation is likely to happen even system parameters exceeds Peterson resonance section, causing half wave inrush current and endangering PT fuse; 4PT wiring and PT with good excitation characteristic can effectively suppress the resonance; current calculated will be more accurate if characteristic of the core at deep saturation is taken into consideration.