Electricity tripping during power cuts

[bungeejumper]

One of the joys of country life is that the power trips out a couple of times a year. I'm told that sometimes it's a fault in the nearby pylons, and sometimes it's because the farmer has turned on his grain drier and sent a spike through the local grid. Where we're different is that our neighbours' power always comes back on again afterwards, but ours goes down for the duration and the RCD has to be reset. No other circuit breakers on the consumer unit or elsewhere have ever tripped.

Last night we were plunged into darkness just as I raised a glass of red wine to my lips (drat), and then it happened again five minutes later, and after that it was all okay. On the clear understanding that I shouldn't mess with this myself, does anybody have any idea what might be going on? Has my RCD got hairtrigger trouble?

Okay, a few basics. Power to our house comes in via an overhead cable to a terminal block identical to this, except that our says BS1391, not BS88:

Our main RCD (the one that trips out) is exactly this model, and it's been there for at least 26 years. Same BS number (4293):

The consumer unit was installed 20 years ago, at which time we had some new ring mains installed and the heavy cables to the shower, cooker etc were renewed. Earthing is via a deep metal spike outside the front door. I couldn't honestly swear that our 150 year old walls don't have any damp in them, but there aren't any noticeable issues. We had the system checked over a few years ago, and it was all declared AOK.

Hmmm, back to the drawing board. Any thoughts?

TIA

BJ

[supremetwo]

One of the joys of country life is that the power trips out a couple of times a year. I'm told that sometimes it's a fault in the nearby pylons, and sometimes it's because the farmer has turned on his grain drier and sent a spike through the local grid. Where we're different is that our neighbours' power always comes back on again afterwards, but ours goes down for the duration and the RCD has to be reset. No other circuit breakers on the consumer unit or elsewhere have ever tripped.

Last night we were plunged into darkness just as I raised a glass of red wine to my lips (drat), and then it happened again five minutes later, and after that it was all okay. On the clear understanding that I shouldn't mess with this myself, does anybody have any idea what might be going on? Has my RCD got hairtrigger trouble?

Okay, a few basics. Power to our house comes in via an overhead cable to a terminal block identical to this, except that our says BS1391, not BS88:
---------------------------------------
Earthing is via a deep metal spike outside the front door. I couldn't honestly swear that our 150 year old walls don't have any damp in them, but there aren't any noticeable issues. We had the system checked over a few years ago, and it was all declared AOK.

Hmmm, back to the drawing board. Any thoughts?

TIA

BJ

Earth connection on the incoming cable?

[AleisterCrowley]

I'm very lazy, but I'd be inclined to get a new RCD fitted. Not sure what the rules in the wiring regs are these days
Perhaps csearle will drop by, and give you some free advice

[jfgw]

A long shot, but is it an active (non-latching) rcd? They are uncommon (and possibly obsolete except for those integrated into some plugs, sockets and adapters) but I have seen an older design of active rcd. Active rcds are designed to trip when the power is disconnected. Has yours always (to your knowledge) done this?

Wylex made similar rcds with different part numbers. I have found WSES, WSEM (as per the photo), WSEVS and WSETM. I did not find any reference to the different part numbers on the web and do not know the difference. Without buying a WSEM version and testing it, I wouldn't know whether or not it is active.

Does your consumer unit have an rcd (or rcds)?

Julian F. G. W.

[Mike4]

One of the joys of country life is that the power trips out a couple of times a year.

I've an idea I'm not that far away from you but my power goes off about once or twice a month rather than a year. Like your neighbour though, the RCD stays on and the only consequence for me is the clock radio display needs resetting to the correct time when I get home sometimes. The clock radio also tells me it tends to stay OFF for five to fifteen minutes although once, it stayed off for several hours so I decamped back to the boat which is self-sufficient in power, obviously. You should get one!

Rather than invest large amounts of time researching and diagnosing, I'm inclined to suggest just buying a new RCD and plumbing it in as a first move. I'd suggest there is a 50/50 chance of this fixing it, and if it doesn't, this reveals good information for diagnosing. Swapping stuff out for new is not particularly intellectually satisfying* but if you just want the job done, it can be the fastest way of fault tracing.

*A good friend of mine used to work in car engine development for one of the big names and they had a rule of thumb in the university lab: "Never dismantle a busted engine until you know what is wrong with it". The idea being that the evidence is always available if you are looking for it properly, and opening the toolbox before you figured it out is a failure of reasoning. They were however, being paid to think about it for as long as it takes!

[Lootman]

One of the joys of country life is that the power trips out a couple of times a year. I'm told that sometimes it's a fault in the nearby pylons . .

We get more power cuts in Devon than we do in London. I always assumed it was because power is undergrounded in built up areas, but usually delivered overground in rural areas.

Airborne power cables are more susceptible to failure due to falling trees, bird strikes and weather related issues. In the US I always notice and am surprised by high tension power cables stretching from wooden poles with hefty looking insulators, to peoples' wooden houses, even in cities. So much to go wrong.

[csearle]

Any thoughts?

Different RCDs have different susceptibilites to spikes on the input side and to inrush currents on the output side.

You have an RCD with a 100mA sensitivity because your Earthing is via the Earth Rod. Any new circuits these days should additionally be protected by RCD(s) with a 30mA sensitivity so it might be a good time to have a new consumer unit as the problem will probably disappear when that RCD is replaced.

There are special "Type G" RCDs available that are more tolerant of spikes on their input.

As far as the inrush currents are concerned then this might also explain why your installation is more prone to the RCD tripping than the neighbour's. Apart from rotating machinery one typical cause of inrush currents is a freezer. (I imagine it is the pump in the freezer that is the actual cause.) So if you have a couple of large freezers this might be causing a spike as the power is re-instated. This in turn can cause RCDs to trip.

Just as a bit of speculation here, if you do have freezers maybe running them via one of those extension leads with built in surge protectors might improve your situation. Might be worth the cheap experiment?

Chris