Experimental Investigation of Breakdown Characteristics of Rod-Plate-Rod Gap Under Impulse Voltage

In power system, there is a special kind of gap composed of floating objects and air gaps. Its main characteristic is that some conductors are in the state of floating potential. For example, during live operation of transmission lines, the operator is in a potential floating state during the process of entering the working potential from the ground potential and forms a combined gap with the conductors and tower. The breakdown characteristics are difficult to summarize and more complex compared to the simple air gaps. The influence of floating conductor on breakdown voltage is different, and the factors are very complex, including size, position, electric field distribution, applied voltage type, humidity and so on. In this paper, an experiment device with the Rod-Plate-Rod gap is designed, the breakdown characteristics of the Rod-Plate-Rod gap under the lightning impulse voltage is studied. The effects of voltage polarity, plate size and position on breakdown characteristics are analyzed. Based on the experimental results, the plate influence on the gap breakdown characteristics is summarized, and the mechanism of the plate on the gap breakdown process is analyzed. Research results have shown that metal plate could enhance the lightning impulse breakdown voltage when the metal plate is in the middle of the gap. In particular, when the metal plate got closer to the rod, the breakdown voltage became lower than the Rod-Rod gap and this phenomenon is related to the polarity of the voltage. In addition, the plate increased the dispersion of breakdown time and changed the flashover route. The research results will have some guiding significance to practical application. The research results will have some guiding significance for the design of combined air gaps with conductors of floating potential.