Question In a substation grounding analysis (using MALT), do I have to model a fence (in MAIN GROUND) if it is connected to the grounding system? And how should I model it?
Answer You should, and normally can, model a metallic fence connected to the MAIN grid in a way that's as close as possible to the real situation. Only the part that's buried needs to be modeled. If the fence has buried metallic conductors forming a loop around the main grid, then you should model it as such. If it consists of an above-ground portion with regularly spaced posts, then you should only model the posts (their buried portion). Remember that all conductors that are part of the MAIN electrode are assumed to be connected together. Therefore, there is no need to model a conductor loop connecting the posts; in fact, you shouldn't model one if there isn't one there in reality, since this buried loop would contribute to the grounding much more effectively than the posts and would lead to a design that is not conservative.
If the fence is not connected to the grid, then it should be modeled in the same way except, that it should be defined as a BURIED structure.