Abstract
Recently, there is greater demand for stable supply of electric power as higher level of our living. It becomes the important problem that the cause and the location of ground fault in distribution line is found out in early stage and the bad part is repaired as soon as possible, if once it occurs. Therefore, the unit for recording the waveform Io of ground fault's current and the waveform Vo of its voltage is installed in distribution substations and same data are coming to be gathered and the establishment of the technology to distinguish automatically their fault causes is hastened.
In this paper, a pew classification method of their wavefprms for ground faults. It is the method concerned with phase plane trajectry for the values of current or voltage and their differential values. It is found from the examinations of ground faults waveforms based on the real data that the waveform of current Io is more suitable than that of voltage Vo for the classification of waveforms at the ground faults and each trajectry of three type waveforms such as sine wave, trapezoidal wave and needle-like wave has each characteristics in its figure. It is also found from the distribution of 167 sampling points on the phase plane that any waveforms at the real ground fault may be classified into three characteristic distribution of the points and it gives the possibility of easy display for the classification of the ground fault causes.
