Hitoshi Sugimoto

Experimental facility for investigation of lightning performance of distribution lines

In order to clarify the lightning performance of a distribution line, test distribution lines and a test tower were constructed at the Mikuni Testing Center of Hokuriku Electric Power Co. in 1999. Using these facilities, we observed transient voltages and current distributions due to direct strokes of natural lightning. Based on this data, we have clarified the following points: calculated voltages and currents using the EMTP agree with the experimental results fairly well; for lightning currents of long durations, however, the reduction of voltages across arresters by energy absorption should be taken into consideration.

Study concerning production of lightning overvoltages on low-voltage power distribution lines

In order to study lightning problems of low-voltage power distribution lines, lightning overvoltage waveforms were observed inside the homes of customers. The cause of lightning overvoltages was examined from observation of striking points by still cameras. Lightning overvoltages of 62 waveforms were recorded by observation over a period of about 3 1/2 years. Observed waveforms can be classified into three types of single polarity (positive or negative), both polarities (which change from positive to negative or negative to positive), and pulsive waveform. The causes of these lightning overvoltages which were estimated from striking points are shown as follows: (1) Induced lightning overvoltages on low-voltage distribution lines. (2) Electric potential rise due to discharge of surge arresters or current of overhead ground wire. (3) Shift of lightning overvoltages from high-voltage side of transformer to low-voltage side, which is due to electromagnetic induction.