The building is in the centre of Edinburgh. It has 20 earth electrodes around the perimeter. Only 6 test points are accessible at ground level and these are all testing between 60 and 100 Ohms. All these 6 test points are surrounded by concrete so there is no chance of improving the test results by introducing soil conditioners or salty water. The 14 remaining test points can't be found. (I think they are concreted over).

If we do a risk assessment on the chance of a lightning strike on this building, I think it would be very unlikely.

What are the clients options?

Do they need to employ a specialist to do this risk assessment?

Do they need to locate and dig up all the test points?

Do they install a new system?

Do they just ignore the risk?

The building has extensive computer installations.

The building has anti surge protection devices in the main switch room.

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keithredpath

Test it as a complete system - the standard allows for that - equally, you don't have appeared to have measured anything that would lead to concern (yet)

The complete system should be under about 10 ohms - testing individual electrodes should impose a limit of about 10 x the number of electrodes installed (200 Ohms in this case)

As for the rest - see above first

Regards

OMS

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Failure is always an option

Edited: 11 December 2012 at 02:18 PM by OMS