Estimation of time parameters of tail chopped lightning impulses - Clarification of the standard IEC 60060-1/2010

The International Electrotechnical Commission (IEC) issued in 2010 a revision of the family of standards IEC 60060, describing, among other requirements, how to calculate the various amplitude and time parameters used to evaluate high voltage impulse waveforms. However, the standards are not clear in some aspects, especially when describing tail chopped lightning impulses. This paper aims at describe in detail how to properly estimate the time parameters of such impulses.