lights go dim when kettle switches on

[Stephen Dawson]

Ben,

Take some free and very good advice, ring your local electricity company, and get them out as soon as possible. You may save yourself a lot of grief.

[The Natural Philosopher]

How does the power come in? overhead from a pole mounted transformer? or underground?.

If the former, get the leccy company to get you a better one.

[The Natural Philosopher]

any sign of a pole mounted transformer?

Or is it two thick wires up that pole?

In either case, contact supply company.

[Ben]

Its two thick wires, all the way up the road from the village.

[The Natural Philosopher]

Mm. Need to have THICKER ones then ;-)

[Doctor Drivel]

Can't you move the village closer?

[tom.harrigan]

If I were you, I would check that all your circuits are in good order. Does removing your fuses disable the circuits in your house as you expect? Do the fuse wires look correct? Sometimes second fuse boxes are just wired like any other final circuit (I have two of those) sometimes off similar meter tails (I have one of those) and sometimes off reduced meter tails (I have one of those too).

The symptoms you describe do seem to indicate a supply problem, but I find that hard to believe unless you are extremely remote. I and two neighboring houses are supplied by the same 25mmish overhead cable. It attaches to my house, then splits into 3. I can't tell if they are boiling a kettle.

T

[tony sayer]

Always seems that overhead has less capacity then what underground does.

Theres a place near here that has Five subs off the same piddly little transformer and the furthest one on the line is some 500 odd yards!..

But he isn't bothered .. as he'd be using candles if he had his way;!..

[Peter Lynch]

I wouldn't say it's a problem, necessarily, just that the cable to his house is a particularly long run. At a friends place (way out in the boonies) I've measured a 12V drop when her 2kW kettle is plugged in. Worse, the UPS starts running when the fridge kicks in. Yes the lights do go dim, mo it's not a problem - just the way of things.

Pete

[meow2222]

through being tired I think!

NT

[meow2222]

Thats what I was wondering initially, a dogs dinner of a wiring job, but with it being a remote property I guess an old underrated transformer o overhead wire would be more likely.

NT

[John Rumm]

That would suggest a supply impedance of something like 1.5 ohms. Which if true, certainly could be a problem for things powered by induction motors (like fridges) since it would mean that they are drawing over their rated current and dissipating more heat in the motor windings. There is also the danger that motors can stall under load at startup (undervoltage can reduce the already limited starting torque).

[The Wanderer]

Ben, you've had two or three people who either work in or used to work in the supply industry tell you to contact your local distribution company, because in their opinion it's a problem with the distribution network.

You've also had quite a few others who all have their own pet theories coming up with all sorts of red herrings.

I know what I'd already have done.

[meow2222]

I can understand pointing out that I was half asleep at the time, but these kind of comments seem a little off beam.

NT

[Ian White]

In practice it's nothing like that bad. We live in such a house, a former farm cottage with a long underground (private) supply from the farm. The farm buildings have a direct drop from 11kV, but the cable to the cottages was laid at a time when farm workers were lucky to have electric light at all, and a 5A socket in every room was sheer luxury. In other words, by modern standards the cable is well undersized.

I keep a calibrated RMS meter on the supply all the time, and off-load we see 250V, which is fine. There is a 10V drop when a kettle is switched on, and ordinary incandescent bulbs can be seen to dim a little. However, most of the lighting is by CFLs and fluorescents, which are much less sensitive.

The slight flickering of the lights is the only practical problem. There's a lot of electronics in this house, a couple of UPSes, several induction motors up to about 1.5kW, and some radio transmitters with power supplies too heavy to lift; but we don't see any interactions such as UPS dropouts, or noticeable loss of performance in the machine tools.

I should add that the internal house wiring is completely up to date, and the feeders to the workshop and cooker are oversized so that additional voltage drops are insignificant. Overall, it's just "how things are", one of the joys of rural living. IMO it still beats the alternative kind of rural supply, which would be an overhead 11kV supply coming right up to the property boundary.

Going back to Ben's OP, it may well be that his 1940s house has an undersized supply cable by modern standards, so it would be worthwhile to see what the supply company can do. The biggest part of the problem is getting them to come out at all. If he can persuade them to come out "because there might be a fault", the blokes on the job might well decide to uprate the cable anyway.

[The Natural Philosopher]

That does not compute. If they are rn on a lower voltage they will draw less current surely?

That is certainly true.

[Ben]

I'm away from home at the moment, but I would be interested to measure the voltage drop before potentially incurring expense (is there a charge for the distribution company having a look?). I'm expecting the drop to be quite significant based on the amount of dimming, but what sort of figure would be acceptable?

[tony sayer]

Just out of curiosity how much of a load can the usual 11KV three phase line support?. I've noticed over the years that most villages just have the one line feeding them!.

We had this problem at a local communications site many years ago. The volts would drop sometimes to around 185! and it was only when the mobile phone companies moved there that it was upgraded.

Presumably these could stand the expense and paid for it to be done!. The 240 volt line in looked as if it was made of bell wire and came several hundred yards over poles from a tiny tranny!....

[Huge]

No. Tell them there's a fault.

Our overhead supply is tangled in a neighbour's tree. I called the supply company (actually, I had to make about 5 calls before I got the right number) and the pod person in the call centre said they'd come much faster if there was a fault. So I mentioned what we've always called "disco" - the flickering lights when a domestic appliance cuts in and out. The engineers arrived the following day and found and replaced a very scorched insulator up the pole that brings the supply on-site. (*)

And the tree? There's a 22 week wait for the "tree gang". We're still waiting. But the lights have stopped flickering.

(*And that I had inadvertently wired the socket in the porch L/N reversed. Damn.)

[The Natural Philosopher]

Quite a lot. Certainly enough for a few thousand homes.

Thats what was general when this type of stuff was installed - you might excpect lights, and the odd heater or two in any given dwelling.