Rules and Guidelines
Want to participate in the discussions? Please read our Community Rules and Guidelines. Need some help? Visit Support and Answers.

  • State Not Answered
  • Replies 3 replies
  • Subscribers 34 subscribers
  • Views 719 views
  • Users 0 members are here
Options
You may also be interested in

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.

Parents
  • 0

    There's a good reason why the protective measure of electrical separation (such a s a shaver socket) is normally allowed to apply only to a single item of electrical equipment. Imagine an environment with no earthing. At some point a fault in a water heater causes the metal water pipe to come into contact with a live conductor (the N say). Perfectly safe, nothing trips, no one gets hurt.

    Now imagine a year later, a kettle (in the same house or even in a neighbouring house) develops a short between its metal case and the other live conductor. Still no ADS. Now someone touches the kettle body with one hand, and a metal sink tap with the other hand. Instant death.

    So it's good to connect all exposed conductive parts together so that a) they're all the same potential and b) something's likely to trip. Then, given that the ground around us is this big wet mass of soil and buried metal pipes, it's probably a good idea to bond that too, because it we don't do it deliberately, it's going to bond by accident anyway.

Reply
  • 0

    There's a good reason why the protective measure of electrical separation (such a s a shaver socket) is normally allowed to apply only to a single item of electrical equipment. Imagine an environment with no earthing. At some point a fault in a water heater causes the metal water pipe to come into contact with a live conductor (the N say). Perfectly safe, nothing trips, no one gets hurt.

    Now imagine a year later, a kettle (in the same house or even in a neighbouring house) develops a short between its metal case and the other live conductor. Still no ADS. Now someone touches the kettle body with one hand, and a metal sink tap with the other hand. Instant death.

    So it's good to connect all exposed conductive parts together so that a) they're all the same potential and b) something's likely to trip. Then, given that the ground around us is this big wet mass of soil and buried metal pipes, it's probably a good idea to bond that too, because it we don't do it deliberately, it's going to bond by accident anyway.

Children
No Data

Join us to get the best from IET EngX.

Joining EngX lets you personalise your experience so you stay up to date on the topics that interest you, plus you’ll be able to make connections who are looking to collaborate, exchange ideas and more.

Join us Not now

Community Rules & Guidelines