Why does high wind cause power cuts?

When  it goes out but then comes back after a second or so the auto-reclosers are reconnecting you. The fault is then either something transient,  which may be as simple as vegetation falling on the lines or wind blowing the rain into the wrong places on very wet insulators, or there is a hard fault that is not reconnected but there is at least one more dis-connector  between you and it that has locked off.


This wikipedia article  has a US centric bias, but broadly similar devices are found on our  rural11kV lines, either staying off after a fixed no. of re-tries in a pre-set period or less commonly having a remote signaling link to tell it to go for a  re-try.

Note that in the UK the 11kV does not distribute neutral, so we have current transformers looking for imbalance, that perform the equivalent of a coarse RCD on the 11kV outbound, so a tree against a line is easily detected. This is 'SEF' - sensitive earth fault tripping. You'd expect SEF trip and re-try to be more common than line to line or line down faults , which would be likely to be flash and a permanent off.


This doc from ENW  explains a typical UK policy -  you may find section 7,4 a good read.

Hi Mike,


Many thanks for the links and description, I must admit I was thinking more about root causes - and for example I hadn't thought about wet insulators. As you say, vegetation seems pretty likely. Sometimes it's just been off for a few seconds, sometimes for an hour or two at a time (since yesterday lunchtime). So presumably not a line down, but something that causes a trip that's sometimes self recovering and sometimes has to be cleared.


Thankfully it's stayed up all evening, and even more thankfully I use a laptop rather than a desktop so have just about been able to carry on working today!


Cheers,


Andy

When it's windy/stormy at our place in France, our power usually goes out at some point. This though is because we're in a very rural area and it's the bushes and tree branches that either take the lines down or tangle into them.


Last year our Mayor had the trees and bushes either side of the power lines up to the village cut back rather dramatically. So hopefully not so many power cuts from now on. ?


On this side of the English Channel, we're always experiencing power cuts in our home in the UK (not in a 'rural' area at all) sometimes just a few seconds or so but long enough for me to have to reset all my clocks and other electronic gadgets! No idea why but the locals say it's been happening for many, many, MANY  years. Odd because in my last home (I lived there for around 20 years) I can count the number of power cuts we had on the fingers of one hand.  5 years in my new home and I'm already well into double digits.

More like high jinks up here.

A strange story of brief power cuts happening on a regular intermittent basis. Apparently it had baffled the DNO for the region for a while. They had monitored the overhead lines and removed many of the overhead tree branches which were considered possible culprits. It made no difference. So they hired a helicoper again to check for any hotspots (not sure how a high resistance joint would cause the system to trip out) While they were flying along the lines they witnessed a group of hefers using one of the supply poles as a rubbing stick, causing the pole to vibrate and the lines to collide, a flash and a big bang and the culprits scampered] off leaving no evidence. It had to be witnessed to be believed.


Legh

I have seen some 11kV wooden poles in a pretty shoddy state over the years.  Some leaning drunkenly, some almost rotted through at the base.  It looks like they wait until the poles fall over before replacing them.

Hi Alan,


Many thanks, the rate of cuts has been dropping off over the last week (despite the weather very much continuing) so I'm assuming the loose bits of trees have now mainly blown off or got burnt off! I guess the relevant bodies sometimes have to get tree branches trimmed or removed, which must be exciting in these conditions.


Thanks,


Andy