Rural protection policy for long overhead networks

The distribution of electricity to rural areas of Northern Ireland is by means of wood pole overhead lines energised at 11000 volts. The lines are supplied from three phase 33/11 kV transformers which have star connected 11 kV windings with the neutral star point solidly earthed. Many people live in isolated homesteads on the land that they farm and this makes low voltage distribution impracticable. 11 kV overhead lines are taken to individual homes and farms each of which has a pole mounted single phase transformer usually rated 5 kVA or 15 kVA. The authors describe Northern Ireland Electricity´s power system protection policy for rural overhead networks