Could proximity to an electricity sub-station be the cause of flickering lights?

[Nick Odell]

A long shot, I know, and this is not in the UK either but I wondered if having an electricity substation immediately over the road could be the direct cause of interference to the domestic lighting or even whether there's a capacitance effect over longer mains cable runs that would smooth out irregularities in the supply.

AIUI in this place high-voltage electricity is distributed to substations where it is distributed at a lower voltage to transformers on the street and delivered to domestic premises at 240v. Their system seems to have a heavy duty 240v supply which provides power to lifts and pumps etc in apartment buildings, factories and businesses and a light duty supply which powers the apartments themselves and ordinary domestic properties.

The actual domestic wiring seems to be on a radial system - no ring mains to be seen. The flickering lights are at an unoccupied house with absolutely nothing plugged into any power sockets: only the lighting circuit is active and when it flickers, they all flicker together. I can't see anything wrong with this wiring, other than that it is a radial system, and I've checked the switches and made sure all the cables were screwed down tight in their connectors. But still, from time to time it flickers - and all the lights in all the rooms flicker together.

It's not a haunted house (probably). I can't think of anything else. Could it be the quality of the electricity delivered to the premises and could proximity to the substation be having an effect?

Thanks,

Nick

[Bob Minchin]

Usually just the opposite. Small groups of properties a long way from substations

on a long line usually have small transformers and suffer from relatively high impedance supplies.

[Graham.]

On Sun, 7 Jan 2018 19:36:59 +0000, Nick Odell coalesced the vapors of human experience into a viable and meaningful comprehension...

It's good that you have posted that, because I have a similar anecdote that I have been meaning to post.

I live in a semi built in 1919 in a suburban area, fed by a PILC cable with TN-S earthling (in case any of that's relevant) from a substation across the road, actually about 100m away. The mains has always been extremely stable, with a meter reading of 245V RMS that hardly ever varies, and I have always put this down to the proximity of the substation.

The substation itself is interesting, I have never seen one like it. It consists of two roadside cabinets, one has doors, I have never seen them open, but I imagine it contains fuses, the other must be the transformer, you can see a concrete block inside with holes.

Anyway, before Christmas we started to have trouble, three or four events, involving different areas in the vicinity, not the "every third house" that I imagined a phase down would effect.

On one occasion there was a brown-out of about 20 min when the supply went down to 50v. All the LED lights in the house continued to work at reduced brightness, and most switchmode wall-wart devices were unaffected but the TVs and fridge/freezer went off of course, and I had the presence of mind to unplug the latter. After 20 min the power went off for a while.

After each event, the power was restored without any local intervention.

A few days later Electricity Northwest excavated around the transformer, and a week or so later this letter was sent to the effected households.

I noticed that the mains voltage is lower now, about 239

It seems like the transformer cabinet that I can see is the tip of an iceberg.

I have some pictures of the excavated substation if anyone is interested, the transformer has lost its signage many years ago, but I think it said Farranti 11kV

I was surprised that we could be "back-fed" like that, as it implies (to me) that the low-voltage side is extended to somewhere else in the network.

[tabbypurr]

Manhattan? Kibera? Cable capacitance won't help you with voltage stability

NT

[harry]

There is a loose connection/faulty switch somewhere.

It needs rooting out, it could start a fire. Sounds like it's associated with the consumer unit/main switches. Could even be before the meter. Or even on the meter.

[Brian Gaff]

1st, no no odd effects like that. Indeed its more likely if it were the other way around, ie at the end of a run with other large loads switching on it. Best guess is first to ask others in the area if their lights do this too. Make sure its a fluctuating voltage issue by looking at a socket as both those and the lights should vary together if its an external issue. Look at the meter and how the line comes in and poke it around a bit with something insulated in case something is loose there. After that and if no other properties are affected then you are faced with contacting the supplier. You don't say where abroad this is, but Out in the middle of nowhere this can happen even here, but since you are close to a substation one wonders if you are actually | to it or from a more distant one. Brian

[Andrew Mawson]

That would be FERRANTI - made in Hollinwood Manchester !

Andrew

[David]

I assume you are asking if the sub-station can induce current in the wiring local to the lights such that A/C flows through the bulb even though there isn't a circuit via the light switch.

Much like the party trick of taking a fluorescent light tube and holding it underneath high voltage wires and seeing it light up.

If that is your suspicion, then presumably you could set up a test system with a light fitting, bulb, and a load of wire running around the room but not terminated at the mains. If that lights up it could give an idea of what may be happening.

I assume the lights are as in the UK - that is switched live and neutral return with no earth wiring involved to complicate things?

Oh, and you could just disconnect one of the spurs from the fuse box and see what happens then.

Or, looking back again, (but confused by the reference to an unoccupied house) are the lights on but then all flickering in time with each other?

Cheers

Dave R

[Dave Liquorice]

implies

Careful, "low voltage" in distribution terms is anything below 125 kV, I think, I sit to be corrected.

At the 11 kV level the network around here is a collection of inter connected rings, with normally made and normally open manual air switches. These divide the rings into sections a few miles long and by altering the switches can isolate a section with a fault quite quickly and restore supplies to properties not on the faulty section.

Being rural most places have their own pole transformer so linking at the 240 V level just isn't going to happen but in towns/urban areas

240 V sections feed from different substations are likely to be quite close together and it wouldn't take long to make a temporary join between them. Probably at the same time as the excavated around the duff transformer, presumably to isolate it and it's switch gear/fuses from the system.

[charles]

Corection: Low Voltage is not exceeding 1000v ac or 1500v dc (BS7671)

[Nick Odell]

I've checked all the terminations in what passes for a consumer unit and all the screws are fully tight. The meter is on the outside of the house behind a glass panel: I'll have to check whether we are a) able and b) permitted to gain access to that. Thanks.

Nick

[Nick Odell]

Well, mainly wondering if a rough supply to/from the substation would still be rough by the time it's been through the local transformer and into the house. I'm hoping that there wouldn't be enough stray emf from over the road to affect anything on our side otherwise what must life be like for the houses either side of the substation?

Yes they all flicker in unison. There can be long periods of constant light, then they all do it for a minute or so.

We are going through the process of sorting out and clearing the house after a death in the family. The house hasn't been lived in for several years and there are no electrical accessories connected to any of the sockets. We are going to have to take a vacuum cleaner over there sometime soon but I don't suppose the vac motor would really register fluctuations of the sort I described.

Thanks,

Nick

[Chris Hogg]

If you plug a table lamp into one of the power sockets, does that flicker? IOW is it just the lighting circuits or does the flicker include the power circuit? If the former, then it suggests a fault within the property; if the latter, it's probably external.

Do neighbouring properties flicker at the same time?

When I had a pottery kiln, only 7kW, but when the temperature controller brought the power in, the house lights would flicker momentarily and very slightly, even with a triac in the controller that switched in at zero crossover volts. Is there some high-power equipment being operated nearby, like a welder, that might cause the lights to flicker visibly? I think the eye is quite sensitive to these things. Is the flicker very slight, or a complete cut-off for a fraction of a second?

[Nick Odell]

We'll give that a try, thanks.

Not so easy to tell because of the common use of window shutters in the hot season.

This is why I wondered whether proximity to the sub station could be a factor. Incidentally, "Substation" could be losing something in translation. There is definitely no generation going on there but it is a sizeable building. I'll try and remember to take a picture next time I am there.

Thanks for the useful suggestions,

Nick