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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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    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.
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  • 0
    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.
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