I'm looking at the risks associated with Earth Potential Rise Risk in TT an installation close to a Pole Transformer. I have read from the various DNO's they specify a distance between the HV earth and the LV earth, this I'm taking is to avoid the EPR from the HV side being transferred to the earth of the LV side.
This is based on sites being close to or within the distances mentioned above.
I have seen sites that have a DNO TN-C-S earth provided, but there seems a risk. In the event of the HV fault, even if the separation between the LV and the HV earths to reduce the EPR transfer to a safe potential. In the TN-C-S earth there will be a voltage on the earth from the HV fault, this voltage will be present at the DNO head cut out. Which will effectively cause a potential between the DNO earth and local earth.
I would consider a TT earth to mitigate the above. While the earth will bring in the Local earth voltage if there is one from the EPR from a HV Fault, it will effectively create a equipotential zone at what evert the EPR is at that point.
Any advise or references would be greatly appreciated.