Tt With High Neutral And Earth Voltages

[stemac]

Came across a new situation that advice is needed on help appreciated

Added a couple of circuits to a existing installation about 10yrs old on a TT system on a property in the countryside

while doing my live tests at the consumer unitI got a reading of 58v between neutral and earth and 182v between live and earth. This prevented my tester from doing a Ze test (because of the N-e voltage the tester thinks its incorrect)

Went to the meter box pulled the meter tails out of the isolator so no load was present and tested live to neutral 240, L to E 218 and neutral to earth 58volts

the earth was taken directly off the earth rod

the client has experienced no issues of rcds tripping etc

it was suggested by my technical helpline  that I call the DNO they arrived and claimed no issues on there side and that it must be a issue with the earth rod as he took a reading of over 200 ohms,

 I have experienced the high earth at a rod before but I have not seen the high neutral to earth voltage

when I go back i'm going to use my old tester capable of doing a 2 wire Ze test to get a idea of the earth resistance (using the spike method will be difficult due to paving/tarmac and the fact I don't have the earth probes for the 3 wire method (never had to do that test in 20+ years)

the dno suggested that I bring plenty of earth rods and a breaker and go deep and find a more reputable earth and that will cure the high neutral earth voltage and let me get on,

1 do you think he the dno is right

2 your opinions so that i'm not wasting mine or the clients time in solving the riddle

thanks In advance

 

[Andy™]

id say you have either a non connected earth or a very high earth. needs further investigation, but either way you could have easily tested Ze with the test kit you have

 

[Essex1]

Welcome.

Well as the DNO are not supplying you with an earth you can hardly blame them for their approach here. With all load off their supply is good. So having a guess the issue is on your side of things.

 

[ProDave]

Interesting one.

Just doing a voltage test, there will be negligible current through your earth, so even with a high impedance earth you shouldn't get that N-E voltage.

It makes me wonder if another customer nearby has a fault and has a high earth current flowing raising the local earth potential?  If so the DNO should take notice.

I would start with trying another rod, somewhere with some decent soil as a test, even if it's the middle of the customers lawn.

 

[stemac]

when i tested with the tails out my connections where direct onto the earth rod, and on the dno isolator live and neutral, so i'm going for a poor earth i coudnt have tested the ze as my tester has a inbuilt polarity checker so the 58 volts neutral to earth ment the tester couldnt/wouldnt allow a 3 wire test to be performed (darn new tester) so i will dust down the old one which can do 2wire ze when i return, don't understand how I could have done one though andy or I am I losing it in my old age but thanks for the helps

 

[ProDave]

but you could have done a 2 wire test?

 

[stemac]

not with the new tester as it only does 3 wire, and looked in manual and no 2 wire alternative offered i suppose i could have piggybacked the neutral and earth lead but dont know if it would have worked or been  reliable i'll do it at home as a exercise i think

 

[Andy™]

but you can do a 3 wire test with 2 connections...

 

[steptoe]

Ok, I'm thinking you don't have any voltage whatsoever N-E 

As ProDave suggests,  you may have a potential E-N 

This would also answer your 182v L-E 182+58=?

Taking into account varying resistances etc,

Oh, and do an Ra on the rod to confirm it's ok, Ze simply takes into account someone elses rod too. 

 

[Sidewinder]

Time for the good old screwdriver in the flower bed methinks?

 

[Tony S]

[SIZE=medium]With a fault from a neighbouring property on a different phase some interesting voltages will show.[/SIZE]

[SIZE=medium]I’m also thinking along the lines of a high resistance neutral common to other supplies in the area.[/SIZE]

[SIZE=medium]Last time I got involved with something like this it took the then NWEB six hours to sort out. In the end I found the fault for them.[/SIZE]