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My house is relatively New, Built 2001 by a National Building Company and wired by professional building contractors. No Electrical modifications have been undertaken and all electrics operate as built.
I recently loosened a Double socket live, and noticed one of the earth leads was loose albeit still located in the earth terminal. The earth wire came out of the terminal and I noticed a small electrical spark at the point of disconnection. There is an RCD installed in the socket ring main and there is No Earth Leakage detected as the RCD has not tripped.
I was puzzled by this spark so I connected a Multi-Meter between the disconnected Earth wire and the other Earth wire of the ring main and measured 90v ac between these two Ring Main earth wires. Before re-establishing the earth ring main, I measured the current through the earth ring and this was 4mA. Clearly there is a high impedance involved in this earth ring presumably associated with the RCD, but my understanding is that the RCD compares Line and Neutral currents and determines any difference would be earth leakage and trip if over 30mA is detected, but there is no direct connection of the RCD to the Earth. Also my understanding is that the Neutral is earthed at the Star Point of the Three Phase supply at the substation. So this 90v ac and 4mA current I am measuring is confusing me and may be normal.
Has any Sparky got any comment on my finding and thoughts, if so, please Educate me ?
I recently loosened a Double socket live, and noticed one of the earth leads was loose albeit still located in the earth terminal. The earth wire came out of the terminal and I noticed a small electrical spark at the point of disconnection. There is an RCD installed in the socket ring main and there is No Earth Leakage detected as the RCD has not tripped.
I was puzzled by this spark so I connected a Multi-Meter between the disconnected Earth wire and the other Earth wire of the ring main and measured 90v ac between these two Ring Main earth wires. Before re-establishing the earth ring main, I measured the current through the earth ring and this was 4mA. Clearly there is a high impedance involved in this earth ring presumably associated with the RCD, but my understanding is that the RCD compares Line and Neutral currents and determines any difference would be earth leakage and trip if over 30mA is detected, but there is no direct connection of the RCD to the Earth. Also my understanding is that the Neutral is earthed at the Star Point of the Three Phase supply at the substation. So this 90v ac and 4mA current I am measuring is confusing me and may be normal.
Has any Sparky got any comment on my finding and thoughts, if so, please Educate me ?