3 phase low voltage??

[Bsharp]

Hi all I was called to a job this morning where the 3 phase supply was showing low voltage on two phases? The voltages where L1-245v
L2-110v
L3-135v
could anybody give any possible reasons why this was the case? I have handed it over to supply company as I thought must be a fault on their side
thanks for any input.

 

[davesparks]

And what was your point of reference for these voltages?

 

[Bsharp]

Between line and neutral at main incoming isolator.

 

[davesparks]

Ok, which side of the isolator and was it closed or open? What was the voltage to earth of each phase and the voltage between phases?

 

[Bsharp]

Measured on both sides of isolator with isolator open and closed, same results between line and Earth.

 

[Deleted member 26818]

Are you in the UK?

 

[davesparks]

And between the phases?

 

[davesparks]

And what earthing system?

 

[Bsharp]

Yes in uk. PME Earth at source TT at consumer side
showin 415v (approx) between L1 and L3
235v (approx) between L2 and L3
Same between L1 and L3

 

[davesparks]

So the installation is TT?
When you measured voltage to earth was it to the PME Earth or the TT?

 

[Bsharp]

They seemed to measure the same on the TT Earth and the PME Earth. The installation is TT correct.

 

[davesparks]

Presumably you meant to say 235 between L1 and L2? In which case I'd be inclined to say that the fault is indeed external and that it is on the L2 supply, possibly a high resistance connection, or something more sinister.

 

[Bsharp]

Sorry Dave yes your right I did. I was leaning towards the L2 fault as well, Scottish power on site now so hopefully some answers shortly.

 

[telectrix]

the rat in the L2 wheel needs as swift kick up the arse.

 

[Bsharp]

Problem solved, well sort of. Yellow phase down cable dangling between to overhead lines in middle of field.