Ze too high on TNS at CU but not on supply

[ianbrookes]

I just had the DNO come out as I was getting a reading of 2.68ohms on a TNS system measured from the CU.
All parallel paths removed.

The DNO measured 0.68 at the supply and changed the earth strap and got it down to 0.48.

Is there any reasons why this is so high at the CU ?

There is an earth bar near the meter which has lost its shine - could this be the problem ?

 

[Plonker 3]

How far from the head is the CU?

Sounds like a bad connection or a break in a cable.

 

[Richard Burns]

If you are measuring direct from the supply tail at the CU then I would suspect a loose connection on the line terminal as it comes in.
If you are measuring through the switch then it may be some resistance in the switch.

Have you tried measuring from the earth bar at the CU, then at the MET and then at the supply earth directly, this should indicate where the change occurs, it may be just a loose dirty connection on the MET if you were measuring from the earth bar a the CU.
Take out all the connections (not the line incomer! just tighten it) clean the copper if necessary and re terminate this should clear the problem.

 

[Guitarist]

Did the DNO try it with their meter where you measured it high?
Just wondering if it's as simple as a problem with your meter, or even measuring using no-trip setting on a 1700 MFT.