Unstable Supply

[mikep]

Have been working off & on this job for the last couple of months and was wondering if anyone has come across something like this, I noticed that the lights dim very slightly at the rate of of about 1 pulse a second, checked it out with the fluke meter and it ranges from 240 volts to 249 volts, also the frequency fluctuates from 49 to 51 hz, wondering what is causing it but have discovered behind the house is a small industrial unit which may be the cause, I was also asked to look at a cooker a few doors away for an old girl and noticed her lights do the same.

Thing is it has gone on a few months now and I may now phone up the DNO to see what they say about it, so has anyone else had this problem.

 

[Zeespark]

No Mike, but I would think that the local DNO would be the best bet in terms of a solution right now. How long has your customer lived at the house? have the units been there long?

AndyGuinness

 

[mikep]

Hi Andy, Bit of a long story as I started the job in october, house was semi-derelict and has had loads of work done by me since then, customer has been trying to sell it for some time and has run out of money a few times but has now been sold, I noticed some time ago that it had this problem but told the client to ring it in as It was a supply problem, anyway have just done a couple of other bits there and it is still the same, just thought I would pop it up on here out of interest to see if others have had similar.

oh yes the units have been there for many years.

 

[Manator]

The rise and fall in the voltage would not cause this, well not at an impulse of 1 second, most probable cause is the frequency variables, which could come from incorrectly installed machinery sending back EMF down the line. If this is a new symptom I would have a look and see if the industrial unit has had a new machine fitted recently, probably a second hand job, and installed by someone not conversant with filters and machine controls.

 

[Zeespark]

Thats fine mate, you have done all you can by advising your customer to contact the DNO.

AndyGuinness

 

[mikep]

I'm not worried, got paid for the work and finished, it has been like it for the last 6 months or more and as I have said been in another house up the road and that does it as well, if I was living there it would drive me nuts,

 

[Manator]

Mike, the distribution on the street will be spread across the same phases as the factory. L1 will go to every other house, L2 to the ones in-between, and L3 to every fourth or so. The problems you describe could effect 1 phase or all 3, the effects will reduce along the length, which means that it may only effect the first two or three houses on that phase, whilst the next suffers from no ill effects. You have done the right thing to advise the client to contact the DNO, they will at least know of a problem, and may be able to find the cause, and make those responsible to sort it out.

 

[Andy™]

also the frequency fluctuates from 49 to 51 mhz,

well there's your problem!

 

[Sidewinder]

Yes the frequency should be at around 50 Hz not 50mHz, that is a very low frequency and definitely a DNO problem!

If it was between 49 & 51Hz rather than milli Hz then it would be well within ESQCR requirements!

] :tongue in cheek :^O :x

 

[mikep]

Oh bugger I meant Hz.

 

[revjames]

I doubt very much that the frequency could be measured accurately enough by any of our instruments.

 

[Sidewinder]

Sorry Mike,

It's just that I am a bit of a units pedant!

Can be very misleading especially mohms and Mohms if you get them the wrong way round!

:coat

 

[mikep]

Quite agree with you, I think it's an age thing, just lately seem to be getting my mords wuddled.