Hi Ze Reading

[DPG]

yes

Didn't you get an IR reading of 0.7M between two of the conductors?

 

[sidekick]

So Ze is 0.16 and Zs is 2.42. Is this measured or calculated by continuity.

measured

 

[DefyG]

So should be looking at a Zs reading of 0.16+0.49 = 0.65? (when energised, but presumably this is an old unused cable) so sticking with expected R1+R2 for now should be 0.49ohms?

I could understand high L-E and N-E measurement if corroded swa at gland or similar but that shouldn't affect L-N measurement which should be about 0.23ohms! unless something amiss with cable?

 

[sidekick]

Didn't you get an IR reading of 0.7M between two of the conductors?

I did. Have since gone back withnewly calibrated tester and done a new clean test. Its quite concerning that the reading is so different. The 63a mcb at origin has tripped out several times but not recently.

 

[sidekick]

So should be looking at a Zs reading of 0.16+0.49 = 0.65? (when energised, but presumably this is an old unused cable) so sticking with expected R1+R2 for now should be 0.49ohms?

I could understand high L-E and N-E measurement if corroded swa at gland or similar but that shouldn't affect L-N measurement which should be about 0.23ohms! unless something amiss with cable?

cable in ground approx 25 years

 

[westward10]

Do some continuity tests to establish where continuity is amiss.
R1+R2, R1+Rn, R2+Rn.

 

[DefyG]

Its quite concerning that the reading is so different.

What IR readings are you getting now?

 

[Julie.]

Ze o

Connections look all clean and tight with origin reading 0.16
Ins res L-E 3.37, N-E 4.27
and N-L 2.36 so not great

You don't appear to be clear with the problems here.

You talk about insulation resistance of 2.36 to 4.27 - is this Mohm?

This is irrelevant to the Zs

You don't appear to know the differences between insulation resistance, Ze and Zs.

If you do have Ze of 0.16 ohm at the feed end of the cable and ~2.5 ohm at the load end, there is absolutely something wrong with the cable or terminations.

I would expect a r1 + r2 of 0.5 ohms or thereabouts.

You need to find this fault, not cover it up by adding rods or anything else.

You need to measure the r1 + r2, the r1 + rn etc. This will show if you have a cable fault. And will identify which conductor is the problem, if they all read 0.5 ohms (less for r1 + rn) then the fault is between the cable feed end and the header. - most likely a bad connection in the earth path.

 

[westward10]

Thank you DefyG
Ze at origin 0.16, zs at annex csu 2.42, total zs on socket circuit 2.67

The Zs for the socket circuit is not relevant your problem is the submain.

 

[sidekick]

What IR readings are you getting now?

Ins res L-E 3.37, N-E 4.27
and N-L 2.36