GB788033A - Improvements in and relating to electricity supply systems - Google Patents

Abstract

788,033. Protective arrangements ; transmission line arrangements. ALLMANNA SVENSKA ELEKTRISKA AKTIEBOLAGET. March 2, 1956 [March 18, 1955], No. 6573/56. Class 38 (4). A power line with phase conductors 6 starts from a station 1 comprising a transformer 2 which is connected to a bus-bar 5 mounted between supporting poles 3, 4, the transformer neutral being directly earthed. On the supporting poles 7 for the power line are located overhead earth-wires 8 which are separated from the overhead earth-wires 10 of the station by means of an insulating link 9 at the pole 4. The wires 10 are metallically connected with the earth network 11 of the station, and the poles 7 are earthed by connections 12 which may be interconnected by a ground wire 13. The purpose of the link 9 is to prevent the passage of excessive current through the wires 8 in the event of flash-over between the lines 8 and 6 in the neighbourhood of the station. The provision of the link 9, which may consist of a thread of insulating material, increases the resistance of the earth fault circuit so that the current therein is considerably reduced. The insulation of the link 9 must be sufficient to prevent flash-over when lightning strikes the overhead earth-line. When a counterpoise wire is located in the ground between the earth connections 12, it may be suitable for this wire also to be metallically isolated from the earth network of the station.