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Expected Ze reading on LV adjacent to a 800Kva transformer ?

So I'm trying to work out some cable calcs for a sub main leaving LV Side distribution equipment sited adjacent to a 800Kva transformer , any ideas what the Ze is likely to be  ? I would think it will be really low 

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  • Which is the correct thing to do where there is no access or a test is not practical. I'm just a bit surprised at the results they have given you, which look like they have takes some real readings but they do not stack up. 
    Mind you, round here (SSE land) they don't usually go and test anything at all, (unless you report fault symptoms or damage as well) rather they read some network performance estimated values from their database - so for example on enquiry nearly all domestic supplies in towns are 16kA and earth loop 0,3 ohms neither of which are likely to be true figures, and certainly not simultaneously true on TNCs or  TT for that matter ...

    Mike