Identification of Electrical Parameters in Large Earth Grids

The conductors in the earth-grid of a large electric power station must withstand for the maximum fault duration, current due to the worst case unbalanced fault. The fault duration and the worst case fault current may be calculated by well known means. However, the division of fault current when it is injected into the earth grid is difficult to determine with confidence. The authors describe a scale modelling experimental technique, which can yield improved data on the division of fault return current within an earth grid. Some results are quoted taken on a 1 : 400 scale model of the earth grid of the Liddell power station of the Electricity Commission of New South Wales, Australia.