How far from the substation is the property? The reason I ask is that I've seen this before where there's possibly a ground fault current on the dno's network probably from the hv side of the tx. Try isolate the cu and check if there's still leakage if there is then you have the same problem as...
The blue is left floating in the contactor enclosure also, the only blue cable used is from the swa (3ph&n) which happens to be the neutral for the coil cct.
I'm sure Andy had just over exaggerated when he said " a puddle of water", I assumed he meant it could be damp which could have the effect the op is experiencing, that's how I interpreted it, just saying.
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