Application of precision digital filters in HV impulse calibration

In the calibration of an impulse measurement system by the comparison method, accurate smoothing of the waveforms is essential. This paper reports the application of high order FIR filters to smoothing of impulse calibration waveforms, paying particular attention to the uncertainty analysis of the smoothing process. Test results of the filters using IEC standard waveforms and examples of applications to full lightning impulses, chopped lightning impulses and switching impulses are presented