Determination technique for wave parameters of switching impulse voltage utilizing digital filter

Summary

Time to peak value of the switching impulse voltage is the time from the origin to the peak point of the waveform. In IEC60060-1, to determine the time to peak value it is mandated that a coefficient is multiplied to the time period from 30 % to 90 % of the peak value because it is difficult to determine the origin and peak points precisely. However, when this method is used, calculation error that is larger than 2 % even in the range of the standard impulse occurs. This error depends on the accuracy of the approximation function that produces the coefficient. The switching impulse voltage is expressed by so-called double exponential function, u(t) = U (exp(-?t) - exp(-?t)). The least square method can be applied to the measured data to approximate them by this function. The time to peak value of the measured curve can be calculated from the approximated function even when the measured data contain a lot of internal and/or quantization noises. To reduce the noise and the superimposed oscillation, a calculation technique similar to the k-factor method, which is used for the determination of the wave parameters for the lightning impulse voltage, is proposed. For the switching impulse voltage, it is found that a filter having the cut-off frequency of 160 kHz shows best performance for several IEC-TDG test waveforms in estimating the time to peak. In this paper, the effectiveness of the proposed calculation method to estimate wave parameters of switching impulse voltage is described by using reference switching impulse voltage waveforms generated by IEC-TDG and by using real test data.

Additional informations

Authors

KRUZHAEV, FINN

Keywords

Switching impulse voltage, Time to peak