Support Knowledge Base & FAQ Question 126
What are the theories behind MALT?
To describe briefly the theory of MALT, you could follow the description in Section 2 (Brief description of the analytical approach) of . You can refer to  for the part of image theory. Basically, all the grounding analysis theory have a similar procedure no matter what kind of soil is involved.
- Green's function problem, namely, point source solution. If the soil model is of a multilayer type, you solve a Poisson equation with the boundary conditions at the soil interfaces. You will obtain expression of the point source solution in a form of an integral. This integral can be transformed into a series if all the layer thicknesses are a multiple of a base layer thickness (note that such a base layer thickness always exists, e.g., h1=2.4, h2=9, h3=15, base layer thickness = 0.6). In fact, this series solution can be directly obtained by the image method. Each series term corresponds an image.
- After obtaining the point source solution, you can obtain the solution for a conductor segment by a simple integration.
- A grounding network can always be subdivided into a set of smaller conductor segments. Based on the Moment Method, you can set up the equation with the current from the segments as unknown and then solve the current distribution.
- Now you can compute the potential anywhere and also other electrical quantities such as step and touch voltages.
The references are in the following. Reference  has a good description of the general grounding analysis procedure which maybe useful to you.
 F.P. Dawalibi, J. Ma, and R.D. Southey, "Behavior of grounding
systems in multilayer soils: a parametric analysis", IEEE
Transactions on PWRD, Vol. 9, No. 1, pp. 334-342, Jan. 1994.
 A.B. Oslon and I.N. Stankeeva, "Application of Optical Analogy
to Calculation of Electric Fields in Multilayer Media", Electric
Technology, U.S.S.R., 1979, No. 4, pp. 68-75.
 J. Ma, F.P. Dawalibi, and W.K. Daily, "Analysis of grounding
systems in soils with hemispherical layering", IEEE Transactions
on PWRD, Vol. 8, No. 4, pp. 1773-1781, Oct. 1993.
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