Unstable air to start the year?/Canterbury Thunderstorm

[mikestormchaser]

Nice video Andrew, heard a lil bit of thunder in there

[Willoughby]

Yeah like the video Andrew!!

[Andrew Massie]

Thanks, you guys!

Foggy, are you really in Darwin?

[Tornado Tim]

He's been there 4 a while now.
You might want to check out the overseas section of this forum to keep up to date with what hes up to.
Allot more existing than what happening here in the NI anyway.
I wish this unstable air would be in the NI more, We need a Southerly!

[Andrew Massie]

I forgot to mention, too, during the storm, I was playing Red Alert 3 (my christmas present!) on Emma's laptop, when there was a flash of lightning, upon which time I received an electric shock from the mouse I was playing the game with! Emma saw the spark, so I wasn't imagining it!

The laptop was plugged into power rather than battery, and the house we stay in gets its 230V from a pole mounted transformer on an 11kV circuit. There's no phone jacks in the house for internet anyway.

The thunder occured 3 seconds later, so the strike was about a kilometre away. My only guess is that the 11kV line had been struck, and the resulting surge went through the transformer, through the switchmode power supply for the laptop, through the laptop, mouse, and me to earth!

The laptop seemed unaffected, still works fine, which we're stoked about, it's only 3 months old.

I'm still confused, and I'm an Electrical Lecturer! As are my colleagues!

[Lacertae]

Could it be something to do with the EMP acting on the transformer ? I know 1 kilometer starts to be quite a distance dor such effect after an EMP but why not ?
Otherwise the option of the powerline being struck sounds correct, but I think it would have created a bigger surge.

[Andrew Massie]

It could be, but I would have had LOTS of shocks if it was EMP... There was LOTS of lightning! And some a lot closer.

True about the surge, but I may not have been the least resistant path to earth.. which would explain why I didn't get burns and the laptop still goes!

[tgsnoopy]

I'll put my money on his laptop power supply being class 1 with the DC output earthed and Earth Potential Rise from lightning current flowing into the Neutral via the supply transformer earth and exiting largely via the house's MEN earth and a little via him.

I've seen it before, it's got me a few times at PCM cabinets and radio sites during my time at Telecom.

But what do I know

[ricky]

Yes from what I've seen looking at the arrangements on a few pole transformers, (I find these things interesting!), any HV arrestor and insulator mounting earths seem to be bonded to the Neutral/Earth ties some distance down the poles, then have common conductors to whatever the actual grounding arrangement is, so would be quite some opportunity for flashover at the arrestors to lift that somewhat, maybe ground cable inductance would allow some fast impulse too above I2R levels?
I think we've got an HV expert on the board here somewhere who would know

[Vertigo]

andrew, looks like you got REALLY lucky.. id be buying a lotto ticket.

[Andrew Massie]

Yes, it IS a class 1 switchmode power supply, so you're right there, tgsnoopy, BUT the house is fed by a pole mounted transformer which is only about 10 metres from the house. The primary of the transformer is fed with two of the three 11kV phases, the secondary is 230V and one side of the secondary is earthed. The house has it's own main earth stake as well.. However, the event occurred at the same time as we were getting 45mm per hour of rain, so earth conductivity should have been fine.

ricky, there's no surge arresters near us in Arthur's Pass! However, there is a wee substation further down in the village which would have some sort of protection in it. But I'm sure the lightning may have hit the 11kV circuit further away from the village again at Temple Basin skifield.

Anyway, I got struck by lightning! Kinda! I'm just glad the laptop still goes!

[tgsnoopy]

In the kind of soil likely to be present there, the situation you describe is exactly what I would expect. I garantee you that Earth Potential Rise was the cause of your shock.

Can you find another suitable explaination?

Do some research, currents causing EPR has killed people by going up one leg and down the other! With lightning the voltage gradients can be huge, thousands of volts per meter.

Lightning is often tens of thousands of amps current and megavolts, gigawatts of energy. What you experienced is only a very tiny fraction.

[Andrew Massie]

Yeah, EPR (see what I did there?!!) sounds like the most plausible explanation, I DO want to research this, I still find the whole event quite mind-blowing!
Have you heard of 'Step voltage'? That's the diameter of dissipation of voltages to earth, common around downed power cables. If your legs are a certain distance apart, there can be thousnads of volts of potential difference between them, which is the kind of phenonemon that apparently kills cows near lightning strikes!

The HV safety manual states that if you have to go near live downed lines, to take little steps!

I AM aware of how much grunt is in a bolt of lightning, thank you! And I am aware that I only got a little bit... Geez!

But thanks anyway, I'll research (when I get time!)

[tgsnoopy]

Yep same effect.

Sorry, It's something I'm very passionate about cause so many in the trades are totally ignorant of it and treat you like you are full of it when you try to portray your experiences.

I guess I'm guilty of tarnishing you with the same brush, sorry about that.

It got me more than once.

As an ex Telecom Technician I often went out in poor weather to restore service. This was much more of a risk than a direct lightning strike.