Operation of an isolated neutral 10 kV system

The Electricity Supply Board, Ireland, (ESB) 10 kV distribution system is in the main operated as an isolated neutral system, except in Dublin, where the 10 kV network has a resistance earthed neutral. The Dublin network is a cabled network. The author deals with the operational practices and procedures used in the operation of the isolated neutral 10 kV system and with the further development of these procedures in latter years. The major part of the 10 kV network is overhead, comprising about 72000 km of single phase and three phase lines, and about 3400 km of underground cables, mainly in towns and cities. The 10 kV LV transformers number 135000, of which approximately 120000 are single phase rural polemounted transformers, of 5 kVA, 15 kVA and 33 kVA ratings