Testing the lighting circuit

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True. Earth that protects the cable and Earth that protects the equipment need not be the same
Please explain.

There is only ONE Earth - and it is usually included as part of the return path to the source of the supply - but not necessarily.
How it is "connected" to "whatever" is another matter.

Re "the term "CPC""
That is not an acronym.
OK.
An acronym is "a word (such as NATO, radar, or laser) formed from the initial letter or letters of each of the successive parts or major parts of a compound term
Hence, I was referencing an "INITIALISM", which is "an abbreviation (such as FBI) formed from initial letters"
Thank you for causing me to seek further information.

So what? You are on a foreign site.
I was seeking further "information".
The CPC does not come into it when an overload occurs.
In the event of an earth fault, by disconnecting the supply, it might prevent someone getting a shock (or the line conductor melting) so could be termed 'circuit protection' - or even protection in the circuit, if you will.
You wrote "The CPC does not come into it when an overload occurs."
An "overload" could be caused by an excess of current between the Line and the Neutral conductors.

It could also be caused by a "fault" connecting the "Line" to an "Earthed" metal object, at which point the CPC/PE would "come into it" and by effecting an "overload", causing the Circuit Breaker to disconnect the "Supply", thus protecting the wiring from overheating and "Life Forms" interacting between the "metal object" concerned and any "return path" to the source of the electrical supply.

Thank you for explaining that MET refers to "Main Earthing Terminal".
(I have now found MET in https://www.acronymfinder.com/MET.html AND in https://acronyms.thefreedictionary.com/MET
Mea Culpa for not finding it earlier - amongst these ACRONYMS, which should also reference INITIALISMS, a term which you have now taught me.)

While, obviously, you may ask what terms mean, I do not understand your belligerent attitude.
I deeply regret if you (or others) have seen any of my questions/responses to be in any way "belligerent".
That was not my intention in any way, shape or form.
I was merely seeking information.

I apologise if I have caused offence to anyone.
 
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You wrote "The CPC does not come into it when an overload occurs."
An "overload" could be caused by an excess of current between the Line and the Neutral conductors.
Yes, so nothing to do with the CPC.

It could also be caused by a "fault" connecting the "Line" to an "Earthed" metal object, at which point the CPC/PE would "come into it" and by effecting an "overload",
That is not (what we call) 'overload' but 'fault current'.
 
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bernardgreen said:
True. Earth that protects the cable and Earth that protects the equipment need not be the same
Please explain.

There is only ONE Earth - and it is usually included as part of the return path to the source of the supply - but not necessarily.
How it is "connected" to "whatever" is another matter.

There is one planet Earth, not all points on the surface are the same voltage. Voltage gradients exist,

There are many electrical "Earths" and there is absolute no certainty that any two will be at the same potential.

If an electrical "Earth" is created from the incoming Neutral of the electrical supply then the potential on that electrical "Earth" could be be tens of volts different from the potential on the planet Earth at that point, it will vary as the loads on the local supply network change. Main reason is voltage drops along the Neutrals in the local supply network cable

,In the worse case of a broken Neutral to the house then the potential of the electrical "Earth" could be 230 volts different from the potential of planet Earth. Lethal to someone standing on planet Earth and touching an "Earthed" metal item.
 

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