Earth faults and related disturbances in distribution networks

The characteristics of the earth faults and related disturbances, recorded in medium voltage overhead distribution networks during the years 1998-1999 are described. Altogether 316 real cases were analysed. The use of subharmonic oscillation and harmonic distortion was investigated, as a means of anticipating 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