Earth Leakage Trip explosive gas environment

That must be one heck of a cable length to loose 400mA by capacitance? Can you guarantee that at least 400mA would always be lost (e.g. during a reduced voltage event)?


I can't help thinking it would be simpler to locate a 100mA unit at the load end of the cable (perhaps in addition to the 500mA at the supply end if needed for ADS) - presumably selectivity between the wouldn't be a particular issue.

  - Andy.

Thanks Andy - that's worth a try.  I haven't actually measured the capacitance, I'm just inferring it from the earth leakage current.  I measured the insulation resistance with DC as open circuit, so I'm assuming it's an AC effect.  The cable is 2 runs about 300 M of very thick 3 phase each about 60mm CSA, so I expect that's why the capacitance is so high.


Stephen

I think you will find there are capacitors inside the thyristor unit,  as in deliberate components with two legs each, probably in a desperate bid to meet EMC requirements.Which side of the controller is the RCD ?

However, even so, 500j ohms of imbalance is a lot - 1uF is ~ 3K ohms a 50Hz and to suggest you have 6 uF more on one phase than the other two is not the sort of thing to be found in sub kilometer cable capacitnace. As a capacitor at mains voltage look for something the size of a small salt celler. example
https://www.lampshoponline.com/6uf-capacitor.html


Realise that if the capacitance to ground from all 3 phases is equal, the net leakage is zero, much like balanced resistive loads have no neutral current.

So I'd be looking if something that should have been be 'neutralled' has been 'earthed' as a wire saving measure, perhaps an auxiliary supply for display or a cooling fan or  a similar c*** up.