Neutral Earth fault on non energised circuit trips RCD

bernardgreen · 16 Jan 2011

WHen there is no fault all the current through any loads on any energised circuit protected by the RCD returns to the neutral bar and from there through the RCD to the neutral incomer.

When there is neutral to earth short anywhere on circuits connected to that neutral bar there is a second path for current to reach the incoming neutral and this second path by-passes the RCD.

In this diagram the CPC is connected to the neutral in the cut out as for a PME or similar supply method. Where the CPC is not connected to the neutral in the cut out the second route is then via the mass of the earth ( earth rod ) to the neutral which is earthed at the substation or transformer.

Neutral_Earth_trip

bernardgreen
16 Jan 2011
48

I was hoping to get this into the WIKI but it defeated me.

JohnnyG · 16 Jan 2011

Much better pic

RF Lighting · 16 Jan 2011

Could you e-mail me the original picture and I'll stick it all into the wiki.

riveralt · 16 Jan 2011

Couple of points Bearnard.

In this scenario is this an example of what could happen or are you saying this is what happens - I refer specifically to the part which states "in the sensor the current on the live lead..."

Secondly, since both live and neutral are classed as live shouldn't the reference to live be replaced by line?

RF Lighting · 16 Jan 2011

And you've spelt grey wrong

bernardgreen · 17 Jan 2011

RF Lighting said:
Could you e-mail me the original picture and I'll stick it all into the wiki.

I don't have have your e-mail but have messaged you with mine.

Grey or gray is not a matter of simple black and white.

bernardgreen · 17 Jan 2011

riveralt said:
In this scenario is this an example of what could happen or are you saying this is what happens -

It is what happens.

Secondly, since both live and neutral are classed as live shouldn't the reference to live be replaced by line?

I used live and neutral as they are the terms most DIY people will be using for the wires. Phase might be the more "appropriate" term for the brown wires.

ban-all-sheds · 17 Jan 2011

bernardgreen said:
I was hoping to get this into the WIKI but it defeated me.

//www.diynot.com/wiki/wiki:creating-a-new-page

//www.diynot.com/wiki/wiki:syntax

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Neutral Earth fault on non energised circuit trips RCD

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