Dom Nunn asks this question, which concerns the type of earthing system used in a water pumping station that is being inspected. It has been answered by the NICEIC(Theme - Distribution Equipment):
Question: I'm currently inspecting a Yorkshire Water pumping station. There is a supply authority transformer on site, which is rated 11kV/415V. From the transformer there are 7 x 1 core 500mm tails and a 70mm earth cable that go to a large (1900A) supply authority main switch located in the Yorkshire Water switch room. The supply authority main switch then feeds the Yorkshire Water main switch gear.
There is a 300mm main earth cable from the supply authority main switch earth bar to the Yorkshire Water main earth bar. There is a neutral earth link inside the supply authority main switch, but no PME labels anywhere.
So, for the purpose of sizing the main equipotential conductors, do I classify this system as a TN-S or TN-C-S?
Please note - I only know of the neutral earth link because the supply authority has left a gland plate off and I can see inside the switch.
Answer: This installation is likely to be a TNS arrangement.
However, the supply authority concerned should be able to supply confirmation of the earthing arrangement to the installation if you approach it directly for confirmation.
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