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Earth Leakage Trip explosive gas environment

Stephen Biddle
Hi All


I have a question relating to the Earth Leakage Trip level for an electric heater, heating natural gas for a generator.  As I remember to level specified in IEC 60079 is 100 mA.  My problem is I have a long run of cable to the heater from a thyristor controller and I have to set the trip to 500 mA to avoid spurious trips due to cable capaciatance to ground.  Does this then not comply with the EIC spec?  My justification is that 400 mA of the earth current are running through the capacitor, so leaving 100 mA for a genuine insulation failure.


Thanks


Stephen
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    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
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    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
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