Earth to Neutral 2 ohm with Multimeter cable disconnected from switch board.

[MarkBarrie]

Earth to Neutral 2 ohm with Multimeter on alighting cct. The cable disconnected from the switchboard.
I am new here and appreciate everyone looking at this post.
I come from an Industrial Electrical background and would like advice on fault finding.
My house has 1 lighting RCD. There seems to be 3 different TPS 1mm 3 core (A, N and E)
I removed each cable and Isolated it to one of the cables. I disconnected A,N,E of this cable from the switchboard. My Megger has an Ohms setting and measures A, N to E individually. It measures 2 ohms between N and Earth.
The following is what I believe is connected to this circuit.
1) Domestic exhaust fans in bathrooms.
2 Outside lights. These are either full insulated spotlights Earth with sensors (these have led ballast) earth not connected to fitting) or batton holders with LED or fluorescent globes plugged into them.
3) Ceiling fans with speed control light switches.
4) LED downlights. These are the type that takes 240V straight into the light. (Not external transformers.)

The cable is an older cable with the earth in the TPS not being insulated.

I have started disconnecting external floodlights and still have 2 ohms.

I would appreciate your feedback on this issue?
1) what is the most likely cause of the issue?
2) What is the best way to efficiently find the issue?
3) What would you disconnect before doing an insulation resistance test?

 

[Lucien Nunes]

UK readers note that the OP is in Australia hence A = Active = Line, TPS = T&E

The resistance is low enough that it is likely a hard short circuit from something like a nail through the cable bridging N & E, damaged insulation on the neutral touching the earthed metal of a fitting etc. Work your way around the fittings moving towards lower resistance, or split the circuit in half, find which half has the fault, then split again etc.

The presence of fans and lights on the circuit will not affect a reading to earth that is this low. Once the fault is cleared and the ohms range reads offscale, then link active and neutral together and do the insulation test from those to earth, so that no test voltage is present between A & N. Again the presence of that type of load shouldn't influence the reading to earth significantly and it should pass.

 

[davesparks]

When the resistance reading returns to 0 ohms, you will have found the appliance that is causing the fault.

No you won't have, if the reading changes to 0 ohms then you will have made the fault worse!

 

[Lucien Nunes]

a damaged fitting or switch

@edgarbell please could you clarify how a faulty switch would cause this problem?

 

[DPG]

Yes, you are correct

Yes, I agree.

 

[westward10]

@edgarbell your profile suggests you are a trainee, is this correct.