Stray voltage in Neutral - help

[SJE392]

I have an installation that I maintain and the DNO have recently changed their pole transformer. Since this change I have been unable to do earth loop tests. The supply comes from a HV to LV transformer and there is a HV earth rod right next to the neutral/earth rod for the HV to LV transformer.

The installation is a TT system with one earth rod. For some reason I get 186V L-E and 66V N-E and 252V L-N at the cut out fuse when the fuse and the neutral are removed.

Could it be stray voltage from the HV system?
And why would this not give me an earth loop reading on my tester?

Thanks in advance

 

[davesparks]

I'd guess that someone hasn't properly connected the neutral to earth link at the transformer.
Call the DNO as soon as possible to get this checked.

 

[TJ Anderson]

It's not giving you a EFLI as Uo is 186v as is below testers parameters.

If you are really getting those readings at the origin if supply then phone DNO asap

** edit ** Dave beat me to it!

 

[Pete999]

I have an installation that I maintain and the DNO have recently changed their pole transformer. Since this change I have been unable to do earth loop tests. The supply comes from a HV to LV transformer and there is a HV earth rod right next to the neutral/earth rod for the HV to LV transformer.

The installation is a TT system with one earth rod. For some reason I get 186V L-E and 66V N-E and 252V L-N at the cut out fuse when the fuse and the neutral are removed.

Could it be stray voltage from the HV system?
And why would this not give me an earth loop reading on my tester?

Thanks in advance

What HV system are you referring to SJE?

 

[davesparks]

186 + 66 = 252 so it seems more likely to me that the neutral/earth link has a poor/floating connection causing it to sit between the L and N potentials rather than it being stray voltage from the HV.

 

[davesparks]

The installation is a TT system with one earth rod. For some reason I get 186V L-E and 66V N-E and 252V L-N at the cut out fuse when the fuse and the neutral are removed.

Are you sure it's TT and not PNB (TNCS), is this the only installation fed from this pole mount transformer?
The reason I ask is that if you are disconnecting things from the DNO's cutout, which you are obviously not allowed to do, you could have caused this dangerous condition if it is PNB.

 

[SJE392]

Are you sure it's TT and not PNB (TNCS), is this the only installation fed from this pole mount transformer?
The reason I ask is that if you are disconnecting things from the DNO's cutout, which you are obviously not allowed to do, you could have caused this dangerous condition if it is PNB.

I have had the DNO out to investigate and they removed the cut out and neutral for me. Also, yes we are the only connection to the transformer.

 

[SJE392]

What HV system are you referring to SJE?

The HV overheads the transformer is off of.

 

[davesparks]

I have had the DNO out to investigate and they removed the cut out and neutral for me. Also, yes we are the only connection to the transformer.

Did they confirm that it is TT? It seems quite unusual for a single service from a pole mount transformer l.

 

[Wilko]

Hi - yes, what did the DNO investigation reveal?

 

[SJE392]

I can confirm it is definitely TT, the DNO say they have tested their supply and it is good... so really don't know.