Experiences on location of earth faults and short circuits in rural medium voltage networks Hans Roman, Hans Hylla, envia Mitteldeutsche Energie AG (enviaM) , Germany

Liberalization of electricity market forces the reduction of costs for networks personell leads to a decrease of supply reliability service quality

Strategy to compensate the negative influences Faster location of faults in MV- networks, because faults in MV- networks have the greatest influence on supply reliability and service level for most of customers.

Conditions in MV-networks of enviaM normal open-operated rings earth fault neutralization mainly rural areas

Technical concept of short circuit location fault information network control center (reactance) digital distance protection relay topology switching states location (spot) of fault for display network data location module Network data base

Visualization of fault location

Accuracy of fault location 2, 3 - phase-fault mean deviation 236 / 229 m maximum deviation 1900 / 1208 m in 90% of cases faulty or neighbouring line section have been located !! Double-earth- fault mean deviation 965 m maximum deviation 3769 m Earth-fault mean deviation 1205 m maximum deviation 2383 m

Results : Service staff is “in sight” of fault spot (short searching route, reduction of local switching operations) Reduction of fault-location time on 30....90 min faster supply-restoration