SURFACE VOLTAGES AND RESISTANCE OF GROUNDING SYSTEMS OF GRID AND RODSIN 2-LAYER EARTH BY THE RAPID GALERKIN MOMENT METHOD

The point matching moment method has been the prime candidate for grou nding system analysis. The regular method yields accurate results as l ong as the segmentation is very fine. This means a large number of bas is functions and frequently requires a super computer. In the present paper, we propose an alternate moment method in the Galerkin's form. T his form is variational (i.e. with error reduction property) which all ows for very few basis functions, resulting in a very fast convergence but still gives less than 2% error in the grounding resistance. Each basis function in this form can be a whole rod with uniform current di stribution, representing a vertical driven rod or a horizontal rod acr oss a whole grid. Such basis functions give good results in the ground ing resistance, it is obvious that they need not give good results in the voltages (ground potential rise - GPR, touch, and step) on the ear th surface near the grid intersections. To correct this, a second type of basis functions namely spheres is added at the intersections. Sinc e the intersections are few, the total number of basis functions is st ill small. With such basis functions added, however, the resulting vol tages now have errors generally less than 4%. With such high accuracy and small matrix size (approximate to 10X10 to 50X50) in the moment me thod it is easy to do parametric studies, even for an extensive ground ing system.