Investigation of the relationship between PD measured with RF techniques and apparent charge quantity of metal protrusion in air

Radical frequency (RF) measurement has become hot point in field of partial discharge detection. However, a big problem that hampers the application of this method is difficult to establish a relationship between data from RF measurement and apparent discharge quantity, that is, use RF signal to estimate the apparent discharge. In this paper, on the basis of the experiment model of metal protrusion, the relationship between RF measurement and pulse current method (IEC60270) was investigated. The relationship curves of energy, double integration, peak voltage, peak-peak voltage, area of the RF signal relative to apparent discharge quantity or the square of apparent discharge quantity were plotted and the optimal regression curve was found out. At the same time, the impacts of voltage and the distance between protrusion and plate were investigated as well. The results indicate that the optimal regression curve is energy of RF signal relative to square of apparent discharge quantity. The variation of voltage has no impact on the regression curve, that is, data from different voltage regress to one line. However, while the distance between protrusion and plate is changed, the slope of regression curve changes according to it and the same energy is corresponding to bigger discharge quantity. The results are valuable to be applied in the field of estimation of the discharge quantity of RF partial discharge signal.