Discuss Hi Ze Reading in the Periodic Inspection Reporting & Certification area at ElectriciansForums.net
Presume you mean Zs? so as per post#2 what is the Ze?Ze of 2.42.
Connections look all clean and tight with origin reading 0.16Sounds a bit high a reading to be due to just the cable resistance? What is Ze at the supply origin? Perhaps poor or corroded connections of the armour?
Sounds a bit high a reading to be due to just the cable resistance? What is Ze at the supply origin? Perhaps poor or corroded connections of the armour?
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
Thank you DefyGPresume you mean Zs? so as per post#2 what is the Ze?
yesIs this the same 100M cable as the one in the link in post #4?
measuredSo Ze is 0.16 and Zs is 2.42. Is this measured or calculated by continuity.
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.Didn't you get an IR reading of 0.7M between two of the conductors?
cable in ground approx 25 yearsSo 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?
What IR readings are you getting now?Its quite concerning that the reading is so different.
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
The Zs for the socket circuit is not relevant your problem is the submain.Thank you DefyG
Ze at origin 0.16, zs at annex csu 2.42, total zs on socket circuit 2.67
Ins res L-E 3.37, N-E 4.27What IR readings are you getting now?
Thank you for the advice..Ze o
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.
You talk about insulation resistance of 2.36 to 4.27 - is this Mohm?
This is irrelevant to the Zs
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
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.
cable in ground approx 25 years
Agree, overall the cable may be FUBARed, however in diagnosing the high Zs the IR results don't help.It may be linked though, based on the information in this and the other thread about this cable. It sounds to me.like the cable is damaged underground and water is getting in, hence the variable IR results which would possibly link to the poor Zs as the armour will be rotting away nicely.
The Zs for the socket circuit is not relevant your
All this, and your previous thread, point towards the submain cable being damaged underground and deteriorating.
No amount of checking connections at each end or other faffing about will make it any better.
You could fully isolate that cable and test it to confirm.
If it is damaged underground then no amount of earth rods or workarounds will fix it. It needs to be either repaired or replaced.
If it has been damaged for a while then water will have got quite a long way along the cable and rotted away a lot of the armour so it's unlikely you'd be able to do simply cut out the damaged section and joint a short piece of cable in, you'd end up digging up many, many metres of it to find an unaffected but of the armour.
Thank you. I do know and that is my plan as soon as I can gain access to the load end earth clamp.Do some continuity tests if you don't know how to do this find some assistance.
Thank you. I do know and that is my plan as soon as I can gain access to the load end earth clamp.
God knows why. Installed 20 to 25 years ago by who knows who ?What earth clamp? I thought this was an SWA cable, why is an earth clamp involved in this?
God knows why. Installed 20 to 25 years ago by who knows who ?
You really need to focus on the length of SWA in question. If it was me I would completely strip down all the terminations BOTH ends and also IR from both ends at 500V minimum.
Ze at origin is a good reading
Reply to Hi Ze Reading in the Periodic Inspection Reporting & Certification area at ElectriciansForums.net
We get it, advertisements are annoying!
Sure, ad-blocking software does a great job at blocking ads, but it also blocks useful features of our website. For the best site experience please disable your AdBlocker.