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Can we do away with earthing?

Adam Seddon

Had a discussion with my colleagues at work today around the theory of removing all earthing.

This is my question:

If I poke my finger into the live terminal of a 230v socket, the line current travels through me, through the floor (earth), back through the earth to the supply transformer (because the transformer star point is also tied down to the general mass of earth) the fault currents travel back into the transformer star point and hopefully the completed path is of low enough impedance to be able to blow or trip the protective device serving the socket I touched.

Now. If the transformer star point WAS NOT connected down to earth, there would NOT be a return path from the socket I've stuck my finger in, back into the star point of the transformer and I wouldn't be able to recieve a shock as there is no complete return path.

Is that correct or not?

So following on from that, my question is: why cant we just isolate all transformers from earth and remove the risk of a "line to earth" shock? After all, this is exactly why we use SELV transformers in bathrooms no????

Obviously you could still get a line to neutral shock, but that's got nothing to do with the question I'm asking here.

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    An isolating transformer with no connection between earth and the secondary winding only works well and reliably for a single appliance. It also gives some protection for a small number of appliances such as an appliance under repair and mains voltage test equipment used to facilitate repairs.

    It wont give significant protection to the multiple loads used a house or a number of houses. In addition to the "two faults" scenario described above, consider cumulative leakage currents. A high leakage current on one wire would render the other dangerous to touch.

    The risks can be reduced by use of a lower voltage to earth, such as the 55 volts to earth used on UK construction sites, or the 120 volts to earth used in the USA. 

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  • 0

    An isolating transformer with no connection between earth and the secondary winding only works well and reliably for a single appliance. It also gives some protection for a small number of appliances such as an appliance under repair and mains voltage test equipment used to facilitate repairs.

    It wont give significant protection to the multiple loads used a house or a number of houses. In addition to the "two faults" scenario described above, consider cumulative leakage currents. A high leakage current on one wire would render the other dangerous to touch.

    The risks can be reduced by use of a lower voltage to earth, such as the 55 volts to earth used on UK construction sites, or the 120 volts to earth used in the USA. 

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