Chris Pearson:
I am trying to approach this scientifically. So my next question is what makes you think that the installation's earthing arrangement is at fault?
I might get drummed out of here for suggesting it, but what happens if the earth is disconnected? Does the hum go away? That may sound like a reckless approach, but if you switch on so that you can hear the hum, then isolate remotely, disconnect the earth, and then re-energize ensuring that everybody stands well back and understands the risks, it ought to be safe.
It won’t go away will it, surely if the problem is leakage current flowing along the signal cable screens disconnecting the appliance earth will just increase the current flowing along the signal cable screen?
Chris Pearson:
I am trying to approach this scientifically. So my next question is what makes you think that the installation's earthing arrangement is at fault?
I might get drummed out of here for suggesting it, but what happens if the earth is disconnected? Does the hum go away? That may sound like a reckless approach, but if you switch on so that you can hear the hum, then isolate remotely, disconnect the earth, and then re-energize ensuring that everybody stands well back and understands the risks, it ought to be safe.
It won’t go away will it, surely if the problem is leakage current flowing along the signal cable screens disconnecting the appliance earth will just increase the current flowing along the signal cable screen?
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