Earth-fault treatment in medium-voltage networks

Despite the accumulation of new know-how and experience, the fail-safe and definite detection and location of earth faults, especially with a fault resistance involved, in medium-voltage power networks remains an intensively researched and, to some extent, controversial topic. Although resonant neutral earthing is virtually omnipresent in Europe as a method of treating neutral points, several technical possibilities exist to detect and treat earth faults. So far, various methods have been applied in the MEAG (Germany) medium voltage power network, and opinion was divided as to which was the best and should be preserved for the future. To inject objectivity into the discussion, the earth-fault detection potential of several methods was tested in over 50 experiments during 1994 and 1995. The paper discusses the currently dominating methods and evaluates major findings from the tests conducted