Power Quality

[amissa]

I received complaints from this one consumer about voltage instability that occurs once or twice a week at their house. It usually occurs at night around 8pm, where the lights and television dims out. Also,their energy savers light has to be changed every 3 weeks. For your information it is a double storey terrace house which takes a 3 phase supply. What is the cause of this problem since only that particular house is affected.

 

[don01]

amissa
are you sure it's just at the one customer?
something is starting up and it's big. or they have a bad connection at supply / meter board area and something in the house is starting.

I grew up in a steel town in Australia in the 70s (god I'm that old!!) and the last thing you did was run your movie projector, super hifi at guess what 8 pm or 8 am just when all the big mills started up & we were 20 miles away!!!

to do in a energy saver (I assume you mean those dinky little bent fluoros that cost more than they save) you would have to be hitting it with high volts rather than low - suggesting an inductive load.

but really there's only one way to deal with it. Get a tech down there and start scratching around. I'd go for the bad connection around the pole transformer.

Please feed us more clues as they reveal themselves.
when did it start
when does it happen
can thay predict it
put a recorder on the mains in (include pf )

Regards
Don

 

[don01]

amissa,
first thought: are you sure it's just that one customer? to noticably dim a tv implies one heck of a drop.
second the timing: I grew up in a steel city in Australia and you did not use your projector hifi etc at 8 pm - the mill boys started up after meal break then & we lived 20 miles away!!
If it's just that house they have a serious connection problem at the mains boards or the pole transformer.
Suggestion: get a tech down there to do a visual inspect, check if they have an inductive load which fires up by time clock. If the fault is developing then it may not dim at every start. (eg faulty star delta starter, dicky contact in heater bank contactor, bad connection stressing at motor start, refridge compressor and bad condensor)
maybe put a recorder in

Please feed us more clues as they come to light
This is interesting
Rgards
Don

 

[jbartos]

Suggestions:
1. Please, provide more info, namely, how long does that problem last, e.g. minutes, hours, etc.
2. An oscilloscope, monitoring the voltage waveform, could reveal the nature of the problem, at least partially.
3. Does it appear on every phase or just on one?

 

[wowski]

There are a few things which need checking.
i) the service to the property. If it is an underground cable the sevice joint may be starting to fail. If it is overhead the connections may need tightening, or checking that no trees etc. are hitting the cables.
ii)The internal wiring may need checking.Electric Ovens are also a favourite cause of trouble.
iii)check if their neighbours are doing any welding, or if there are any large electrical machines in the area.

What we usually do in these cases is to install a voltage recording device at their meter board. This records the voltage and current over a set time period, and shows whether the fault lies in the house or is due to some external influence.

 

[amissa]

Thank you sooo much for the advice and tips for the problem on power quality affecting one particular house...We went down to that particular house and found that the cut-out fuse connection was loose ( not properly fit in the housing), also the neutral link was not tight. The same problem occurs on their distribution board - loose wire connection. I guess that was what causes it...i'm waiting for the feedback from that customer. Thanks once again.