Earth faults and related disturbances in distribution networks

This paper describes the characteristics of the earth faults and related disturbances, recorded in medium voltage overhead distribution networks during the years 1998-1999. Altogether 316 real cases were analyzed. The use of subharmonic oscillation and harmonic distortion was investigated, as a means of anticipating of faults. Arcing faults made up at least half of all the disturbances, and were especially predominant in the unearthed network. Fault resistances reached their minimum values near the beginning of the disturbances. The maximum currents that allowed for autoextinction in the unearthed network were comparatively small.