Lightning strike

[whisky-dave]

Anyone have any idea what sort of voltage etc. this might have been.

On Friday 25th July 2014 about midday in E17 London a friends flat got hit by lightning via their roof aerial. The arail itself doesn't appear to be damaged.

It appears that the lightning went down the aerial cable to the aerial plug which was connected to the inline attenuator, the centre pin of the aerail plug was found about 5ft away it must have been very hot as it embedded it self info the carpet leaving a black burn mark around it. The aerial plug/attenuator had been connected to the DVD recorder which no longer functions. The aerial plug/attenuator/lead had been separated in the 'blast' even the aerial plug had been separated from it's lead. I think th e surge then went either through the SCART lead which didm't appear damage d to the 42" LED TV which no longer works although there's no sign of physi cal damage. The surge seems to also have gone down a HDMI lead from the TV to the TV cable box, destroying that although the only physical sign is whe re I pulled out the HDMI lead. it also appears to have travelled through a

2nd HDMI to an adapter to a G5 iMac as the TV was connected as a 2nd monito r. The G5 iMac no longer works although it sounds as if the HD spins up. Th e virgin media super hub 2 was also knocked out as this was connected to th e TV via an ethernet cable. A set of speakers were also found to be not wor king.

It also appears that a cable distribution box out in the street was also hi t as an orange glow and flash was seen at the time.

Photo 1 Damaged to the ~5mm diameter aerial lead Photo 2 Aerial plug and attenuator Photo 3 Aerial plug and attenuator & centre pin Photos 4&5 Fuse had vapourised just leaving the metal end caps, and it also blew off the plug top. Photo 6 The HDMI lead from the TV to the cable TV box, this end was connect ed to the cable TV box, it took a bit of pulling to get it out and the inte rnal pins of the cable TV box came out with it. The cable TV box was no longer working.

[Dave Plowman (News)]

The day after we had that amazing lightning in London - the like of which I've never seen here before - the audio amp in my workshop was dead. Both channels. Power supply was just fine - both input chips which do the balanced to unbalanced had failed. The schematic I drew of it when designing/building it was dated 1997, and it's worked fine every day - and for much of each day ever since.

Everything else in the house seems ok - but of course I might come across something little used at a later date.

Could just be coincidence, I suppose. Simply replaced them and it's been fine since.

[Brian Gaff]

Well really, almost everything in a house is usually trashed. I do know for example that down my street the company I worked for was struck while i was coming out for my lunch break. It had lightening condutors all around it, but none of the computers ever worked again, it even trashed the coffee machine in the lobby.

As you say, some things look like they have been damaged, but most just stop working and often so much of their innards are trashed, its not worth fixing them, cost wise. sorry to say, but Lightening is one of the most destructive natural elements that can in the shortest time ruin our tech. It does not do humans much good either. I used to work back in the old days of the 60s, at a now non existent tv rental repair place in sw London, and when stuff used to arrive back from places like the Welsh hills with lightening damage written on them, it was a bin job. Holes in pcbs, Charred capacitors and melted plastic bits and pieces. In one case where the cable input transformer was was just a chared hole.

Brian

[Harry Bloomfield]

whisky-dave formulated on Monday :

That looks more like the result of a near strike than a direct on.Almost a couple of decades ago our local church tower (stone built)

100 yards away was struck, it did considerable damage inside the church tower.

The resulting pulse, at around 2 in the morning, blew my large sat system, a video and several other items. It either the pulse or the noise, lifted me off the bed. It also took many phone lines out in the village.

[The Natural Philosopher]

Anyone have any idea what sort of voltage etc. this might have been.

Yep. Insurance claim on *everything* including the new house wiring they will *insist* upon.

Take everything that don't work to a fixer of said items, get quotes and if less than replacement get fixed, otherwise replace.

Months of hassle ahead/.

Good luck

[Dave Liquorice]

Personally I don't think they got a direct hit, maybe a streamer with the main stoke(s) hitting close by.

As others have said a direct hit does tremendous damage not just to electronics but the structure and fixed wiring. It's not unknown for all the fixed wiring to be instantally vapourised and blow itself out of the walls.

Your description of minimal damamge to some zapped, interconnected, electronics is more a kin to the affects of a near by strike. "near by" meaning up to a few hundred yards.

Get 'em to go through every single bit of kit in the place and make sure it a) works b) shows no sign of damage. Anything that fails bung in an insurace claim for.

[ss]

So should we disconnect stuff if there is a nearby electrical storm? I am on cable so no dishes or aerials. If the answer is yes, is that unplug as opposed to just switch off?

[Bill Wright]

Items damaged by lightning then repaired often fail again before long.

Bill

[tony sayer]

In article , Brian Gaff scribeth thus

Nope. Sure doesn't. It does need handling with care and if its done right then it can be contained to where it needs to go and thats passing by all your expensive kit.

Radio and TV stations and Cellphone masts are designed to cope with it they simply have to as such high structures are more likely than not liable to be walloped and they can't be out of commission for that reason.

Good levels of protection aren't cheap and in an "uncontrolled" discharge the currents will just go where they find least resistance path and usually many more than the one of them.

Usually .. except that someone I know had the TV aerial walloped not directly, that was the house a few doors away, took out their FM tuner and they gave me the Audiolab amp which just had a blown fuse and a bit if charred track, mended that and been fine ever since:)...

The current had come down the Tuner phono lead looking for an earth and found one across the input PCB tracks to the earth wire and that was that.

[tony sayer]

Blimey!, what do you wear at night metal pants;?..

Unplug it, it may not make a lot off difference in a direct strike but for a nearby sideswipe it can make the odds more in your favour.

My Gran used to put the aerial lead to her valve "wireless" in a large glass jar to keep natures leccy in;!...

[John Williamson]

Unplug, leaving a sizeable gap between plug and socket. Not forgetting the connection to your cable connection, even if it *does* run underground. Switching off just leaves a nice spark gap inside the switch.

Or, if you're in a town, do the same as everybody else and take your chances that it'll be the next street but one that gets zapped.

[Martin Brown]

Worth checking fuses you might be lucky with some of them.

That could be damage due to induced current flowing in the local loop.

I'd hazard a guess at around 1000A pulse current with the voltage not well defined. I have been in a building that took a direct hit once and it vaporised most of the phone lines blowing the trunking off the wall. It took about a week to be repaired and the switchboard operator was inconsolable and quite alarmingly deaf for a day or so. It did curious damage to the local mainframe too. The transient protectors protected themselves by allowing more expensive components to fry first :(

The annoying thing was that there were supergrid pylons taller than our building nearby that didn't get hit at all. It was found afterwards that some scrotes had pinched the bottom 20' of our lightning conductor.

On another occasion at about this time of year I narrowly missed seeing a display of ball lightning witnessed by other physicists.

You really don't want to be too close to these events. Tree trunks can explode from internal steam pressure generated in a direct hit.

Regards, Martin Brown

[Dave Liquorice]

I'd go for the noise and a hefty whack "fight or flee"...

storm?

I switch off the ADSL modem but that's nothing to do with trying to stop it being zapped. It's to stop the electrical noise inducing resysncs and pushing the speed down. It'll recover automagically but may take a day or two.

Maybe but if there are other cables besides the power they'll get hefty induced currents and voltages in 'em, enough to zap input/output stages. TBH disconecting everything is too much faff, have tested and configured spares for key bits, like ADSL modem, network switch and insurance. If lighting strikes there is not a lot you can do without spending serious amounts of money.

[Harry Bloomfield]

tony sayer laid this down on his screen :

I've no idea what caused it, but I woke up landing back on the bed, whilst hearing the massive thump.

[Harry Bloomfield]

My mother used to cover all of the mirrors over ????

[Harry Bloomfield]

ss has brought this to us :

The chances of a direct strike for most people is very remote, but it depends on your location and whether there are other close higher buildings.

Tall buildings will attract the main strike, but will increase your chances of suffering the pulse damage.

Generally you have much more chance of a near local strike causing damage simply due to the EM pulse, than a direct strike. Any cable or wire which travels any distance can pick up the pulse, which can then make its way into sensitive modern circuits and blow them. So disconnect any antennas, phone cables and unplug items from the mains.

Having said that, I have an absolute mass of electronics here and lots of antennas, but despite having suffered quite a lot of damage in the incident I mentioned earlier, I soon became fed up of unplugging things and now no longer bother.

[Mike Barnes]

When I was a student in digs, my landlady would rush to replace any failed light bulb, otherwise it would "fill the house with electricity".

I assume she grew up with gas lighting and didn't quite grasp the difference between a bulb and a flame.

[mail-veil]

Arriving at my house in the middle of a storm I witnessed ball lightning rolling quite slowly across the roof tops; a truly eerie sight. Luckily I had all my amateur radio kit disconnected except for the rotator control box. Every component was physically destroyed and all of the copper PCB track was vaporized onto the inside of the casing. The only other damage was a power diode in the TV and pre-amp IC in the Hi-Fi. We got off lightly compared to some neighbours.

Mike

[Brian Gaff]

PS, the only item I had trashed by lightening was a fax machine which went on churning out blackened paper till I pulled the plug. It was repaired under warranty as apparently the surge protection had been left out of a batch which included mine! I was on BT then and it was assumed the induced current in the line which ran overgound was to blame. Brian

[charles]

If you unplug during the storm, the lighting strike might come ast the moment you have the plug in you hand, Not good.