Earth Grid Research Articles

An earth-gridded SSM/I data set for cryospheric studies and global change monitoring

An earth-gridded SSM/I data set for cryospheric studies and global change monitoring

High-voltage earthing system design and performance

The earthing system of an electricity substation is of the utmost importance, primarily to ensure electrical safety for persons working within or near the substation and also to limit any electrical interference with third-party equipment to acceptable values. Adequate forethought can help prevent unwanted surprises and avoid unnecessary and sometimes retrospective expenditure to achieve an adequate earth grid impedance value. The process starts with accurate soil resistivity measurement and the derivation of an electrical equivalent of the soil structure at the site. This in turn enables the options for achieving an adequately designed grid to be assessed in order to find the most economic solution.

An innovative analysis of earthing grids for power substations

An innovative method for the determination of the earthing resistance and the touch potential of an earth grid for power substations has been developed in the paper. In the new scheme, each conductor of a given earthing grid is treated as a lossy transmission line. Input resistances of representative earthing grids have been evaluated, and good agreement between the data determined by the new method and the latest results published in literature has been observed. By plotting the potential variation on the earth surface three-dimensionally, the potential dips at the centre of each conductor mesh can be depicted, and with which the touch potential of the entire grid can then be enumerated.

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.