all lights in building intermittently flickering

[king_11]

I'm at a large factory and they are complaining that all the lights flicker now and then. I've tested between earth and n at the intake and the voltage is fluctuating between 20 50 volts which isn't that bad but we are going to check all n connections where we can. Could be a supply problem?

 

[telectrix]

what's the L/N and L/E voltage readings?

 

[king_11]

Stable readings mate 235v

 

[Knobhead]

The figures don’t make sense 235V L/N L/E, but fluctuating 20/50V N/E.
Get the DNO in pronto.

Out of interest is this a three phase supply?

 

[king_11]

Why? Yeah they are coming in today. yeah its 3 phase

 

[Knobhead]

I’m concerned that for a start you think 50V N/E is quite acceptable.
L/E may stay stable, but L/N must be fluctuating.

 

[Engineer54]

You say this is a large factory, .....Got any ''Large Motors'' starting and stopping?? also is there any facility of Static or Auto capacitor banks at the main intake?? Both can cause problems with voltage fluctuations, the latter when not set-up properly....

 

[king_11]

found the problem, had the DNO out, had a floating neatural !

 

[Engineer54]

found the problem, had the DNO out, had a floating neatural !

How pray did that happen then??

 

[Knobhead]

Good question E54.

Please let us know the answer King_11.
PS exactly what I suspected, but you were evasive in giving an answer.

 

[Amp David]

Wouldn't be holding my breath waiting for any reply to this thread from the OP TBH

 

[Engineer54]

I'm thinking ....Large Factory, = Electrical Supply from 11KV via DNO or factory owned transformer(s). Very unlikely the DNO will provide a LV 400/230V to a large factory... lol!!! Cheaper unit charges too, when being supplied at MV tension. ..lol!!

 

[king_11]

Wouldn't be holding my breath waiting for any reply to this thread from the OP TBH

just waiting for the report my friend and ill post it up

 

[Amp David]

No probs King. Wasn't meaning any disrespect to you, just that it seems to happen alot, someone posts an issue, and we never hear back to see how or what was done to rectify their problem

 

[shocking_eg]

lucky they found that neutral - could have been a mess if it got hot - iv seen some big 600A supplys melted at the terminals :S