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I am working with a conductive appliance that a user will be in constant contact with over extended periods of time and the appliance is constantly earthed. These two facts cannot change, other than in a circumstance where the user may be in danger.

My question is whether or not it is safe for someone to be in constant contact with the earth line over extended periods of time.

I have heard some people saying that if there is a power fault or some sort of electrical issue (even a lightning strike) that this could in fact be dangerous, yet I have also heard that it is completely safe and that bathtubs are earthed and completely safe.

I recall that in the past I have felt some sort of low voltage tingle when directly contacting a ground pin which was possibly a result of an electrical fault somewhere in the house and this concerned me a bit for this application.

Is it possible to detect stray currents in the earth line and activate an earth circuit breaker at such an event? Is there a sort of safety feature to prevent unlucky circumstances occurring when in contact with earth? Also, would a setup like this break any health and safety regulations?

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closed as unclear what you're asking by Dave Tweed May 3 at 18:34

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  • \$\begingroup\$ Disconnecting the earth line when there is a current on it does not sound safe. Can't think of any suggestion to do that in the regulations I read. \$\endgroup\$ – Solar Mike May 3 at 13:16
  • \$\begingroup\$ There is no current on the actual appliance, it is purely connected to the ground. The appliance does not use electricity at all. Cheers \$\endgroup\$ – Isabella May 3 at 13:17
  • \$\begingroup\$ What kind of appliance uses no electricity at all, yet has a connection to the electrical system? \$\endgroup\$ – Dave Tweed May 3 at 13:41
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The safety of an "earth" and the protection given by it is dependent on how good the earth is. This requires a low resistance connection to the area under your feet that fault currents could flow to.

This is heavily regulated in most jurisdictions and it will be OK to be connected to earth in these places.

I have lived in areas where this is not good due to either very dry conditions giving poor earth connectivity or places where grounding is treated in a very cavalier manner. In these areas caution is necessary.

A RCD detects mismatch between the supply and neutral current and will trip if some of a fault current is flowing through you to earth. It still requires a good earth to work properly. A limitation of these devices is that they will not protect you against a direct L-N fault and the absence of a good earth increases the likelihood of this situation.

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In every household (at least here in Europe) we have a device called RCD (Residual Current Device) which breaks the mains circuit if a current bigger than ~15mA is flowing through the earth line.

The question if touching earth for a long time is safe only depends on how "good" this earth is, i.e. how much voltage drop will result if a high current like a lightning strike flows through it. So this question can not be answered without knowing the magnitude of the faulty current and the conductivity of this earth path.

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    \$\begingroup\$ Through the earth line or to earth? Isn't the rcd detecting a difference of current between supply and neutral so any flowing to earth... \$\endgroup\$ – Solar Mike May 3 at 13:23
  • \$\begingroup\$ @Solar Mike Yes, the RCD detects a current difference between supply and neutral, which means there must be flowing some current through an earth line, which can be a grounding rod, a mechanical housing or even a person's body ;-( \$\endgroup\$ – Stefan Wyss May 3 at 13:32

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