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Seek Advice on post-storm electricity issue


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#1 FabricOfLife

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Posted 14 September 2017 - 06:08 AM

I seek advice on how I could have prevented the following catastrophe :

I was monitoring a storm that was approaching and had unplugged everything. I do this because thunders strike very close to our house. Last time one struck I had to replace motherboard, graphic card, router and the phone socket. The lan cable was black and fused into the motherboard lan port. The technician told me he had never seen something similar in his entire life.

So I was monitoring the storm and unplugged everything before it arrived. I had left one end of the phone cable into the wall socket and the other end was loose, not plugged into the modem.

During the storm a thunder struck very close. I mean VERY close. It could have been 20 meters away. We also had turned off the main power switch of the whole house. When it hit I saw a bright light coming out of the loose phone cable. I had seen this before, when the thunder burned half my pc.

When the storm passed,I had a look at the phone cable which wasn't black. I even touched it to check for... hmm electricity (maybe a bad idea).

I thought I am probably paranoid switched everything on and plugged the cable into the router.

Well from that moment the lan ports stopped working. My provider did some tests, made me plug the two sides of a lan cable into two modem ports to check it and sent me a new modem.

Guess what, I still can't connect via ethernet and I suspect the motherboards lan port got damaged as well.

I hope I won't have to replace the whole motherboard again.

So this whole catastrophe occured even though I thought I had taken sufficient measures to protect my equipment from the storm.

What did I do wrong? And how could this have been prevented?

Thank you for your time.

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#2 The-Toolman

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Posted 14 September 2017 - 07:18 AM

Hey FabricOfLife,

 

If you are removing all lines from utilities prior to electrical storms than you have done all you can do.

 

Nothing can protect any electronic devices from a direct lightening strike through the utilities lines even if the lightening strike is some distance away.

 

Lightening creates a static electrical discharge and sometimes that is enough to destroy anything electronic connected or disconnected.

 

 

 

 

   

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#3 FabricOfLife

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Posted 14 September 2017 - 07:37 AM

Thank you for your reply.

Wow. The static electrical discharge can
affect disconnected devices?

I am thinking that this must be discharge stored in the phone cable, otherwise why would only the lan ports of the router and the pc get damaged?

Is this static electrical discharge dangerous for people?

Could it be that if I had unplugged the phone cable from the wall socket, there would be no discharge stored? Or was there anyway to release it elsewhere than in the modem?

#4 JohnC_21

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Posted 14 September 2017 - 08:19 AM

You probably got an EMP pulse. 

 

http://www.edn.com/electronics-blogs/brians-brain/4435969/Lightning-strike-becomes-EMP-weapon-



#5 The-Toolman

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Posted 14 September 2017 - 08:19 AM

The static is created at the actual time of the lighting strike from what I understand and and I'm no scientist or physicist.

 

The static discharge isn't stored anywhere although during electrical storms it seems to be around everywhere lightening is.

 

Perhaps this will help as I'm not good at explaining things when I have to explain via writing.

 

https://en.wikipedia.org/wiki/Lightning#Discharge

 

Read this part.

Transient currents during flash

Linux Mint 18 Sarah Xfce (32bit) / Hp-pavilion-m7267c / Intel Pentium D Processor 820 Smithfield (2M Cache, 2.80 GHz, 800 MHz FSB, LGA 775 Socket) / Mobo: ASUS P5LP-LE, (Lithium-UL8E) / DDR2 Memory 4.0 GB, 800 MHz FSB / Graphics Card: ATI Radeon X600/X600 SE, (AMD/ATI) RV370 PCIE.

 

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#6 mightywiz

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Posted 14 September 2017 - 10:51 AM

physical landline's have voltage on them at all times, so when you shut power off to the house your phone line still has like 70 volts on it.



#7 FabricOfLife

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Posted 14 September 2017 - 11:01 AM

Yeah, just when the lightning hit, the phone cable was not connected to the router. I can't understand how its supposed to have damaged it when it was not connected.

#8 Chris Cosgrove

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Posted 14 September 2017 - 05:48 PM

Forget the thunder, that's a side effect and only deafens you and scares you out of your pants, it's the lightning strike that does the damage. Lightning is plasma discharging static from the earth to the sky. I have seen the numbers but don't remember them exactly but they are something like 2MV at 100KA. That current passing through a conductor - the plasma - generates a truly impressive electro-magnetic field around it which will induce currents and voltages in any conductor within effective range and I would say that at 20m you were well within range.

 

Any bit of wire, but the longer the more, in your house would momentarily at least generate a voltage. But this would be a bi-directional pulse as the field was created by the strike and then collapsed after it passed, so you would get a current trying to flow in one direction and then trying to flow in the opposite. Semi-conductors do not like voltages applied in the wrong polarity. If all this strike did was take out your modem and your LAN port you got off fairly lightly.

 

As The_Toolman said, you did all you could in the way of disconnecting stuff. With a strike at 20m I personally would be grateful that there were no human caualties.

 

Chris Cosgrove


I am going to be away for a couple of weeks from Sunday 24 September with variable internet connectivity. PMs may not be answered as promptly as usual.


#9 mjd420nova

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Posted 14 September 2017 - 06:57 PM

Lightning can induce a voltage into a wire as short as two inches.  And the strike only needs to be within a mile.  I operate an amateur radio station and have multiple grounds for the home electrical system, the station and the computer gear.  The radio antenna is isolated from ground by an adjustable length to it's own ground so I can manipulate the apparent distance of the antenna above ground.  I have a voltmeter between the three terminations and have measured up to ten volts difference between them.  This is not induced voltage but an actual current flow through the earth. Lightning is funny stuff, it begins in a cloud but has an affect on the ground surrounding the area and will actually create a ground strike, a leader that erupts from anything on the ground and goes off into the sky, attempting to reach up to a strike from the cloud.  I use surge protectors, lightning arrestors and isolation circuits for the phone and cable lines that come into the house.  All of the protection is a one shot deal, once struck it is no longer capable of providing any protection, junk in otherwards.  Just this last week there was a huge lightning event that took out  two isolators for the computer gear, one a surge protector and the other a lightning spark gap, both fried.  No damage to any equipment so the protection works.  Strikes into power sources is the most common but phone lines and cable have vulnerabilities too, any outside lines or gear is at risk.  It is possible that the phone cable reached a potential that hadn't bleed off by the time you attempted use, or that the incoming lines are fried, shorted and causing your faults.






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