I am involved in a project requiring a 66kVA generator as a standby supply to to a control panel. I've read quite a few posts about earthing, but came across what seemed to be a contradiction regarding the earth electrofde resistance in Topic Title: life safety generator earthing.
I realise that a separate earth electrode is required, but what should be the resisstance of the earth rod. In the post it reads "The earth rod resistance needs to be low enough to operate your ADS promptly for an LE fault, even if the DNO earth is absent", but in another it says "Provided the generator supplies a TN-S system (as would be usual), the rod won't be involved in passing earth fault currents, it merely references the N to earth, so it's resistance to earth isn't at all critial. From memory BS 7430 recommends < 20 Ohms".
Can anyone clarity?
