10/350 lightning test waveform in focus

Dr. Karl Berger was a Swiss researcher whose work on Mt. St. Salvatore rates him the title of “father of direct lightning research.” He documented his findings in an article published in ELECTRA magazine in 1975. Some 40 years later the IEC immortalized that work by characterizing it as the closest representation of the actual lightning flash and using it as the basis for the parameters of the 10/350 Class 1 test waveform adopted in IEC 62305-1 “Protection against lightning”. This paper examines the content of Berger´s ELECTRA article and the process by which info extracted from that article led to the formulation of the 10/350 test waveform. Five widely held assumptions about lightning parameters which have been inferred from Berger´s article are examined. When the data that underlie them are scrutinized, four of those five assumptions are found to be unsupported by fact. Finally the paper offers some expanded proposals for testing surge protective devices that rely on more than the exclusive use of a single testing wave form.