I live in a country that follows the UK mains specification, where there are 3 pins on a wall outlet with the topmost pin being earth/ground. Now, is it possible that during a lightning strike, extra voltage from the lightning travels up the earth or ground wire to the mains outlet and to any equipment connected to the mains?

I am asking because, during numerous occasions, with my desktop computer plugged in (not switched on), during a severe lightning strike, I can hear and see a spark somewhere on the casing of the computer, although no damage is suffered. I am wondering might this be the result of lightning voltage travelling upwards through the earth / ground wire to my computer thus causing this phenomenon? Or are there any other explanations such as extra electromagnetic effect during a strike, etc.?

  • \$\begingroup\$ Q. Where does the 800lb gorilla sit? A. Anywhere it wants. Q. Where does the lightning strike go? ... \$\endgroup\$ – user_1818839 Mar 14 '16 at 12:30
  • \$\begingroup\$ I believe the question is about secondary effects of a lightning strike. If lightning hits your house, say goodbye to whatever it chooses to travel through. (Happened to my neighbor: the conduits in the wall with copper cable inside exploded). But if it hits your neighbor (happened to me :-) ), then you can see induced currents due to the fast changing magnetic field associated to the lightning's current. These can be somehow managed and prevented (actually prevented is not the right word). And I guess these are the effects lamented by the OP: every loop will act as an antenna. \$\endgroup\$ – Sredni Vashtar Mar 14 '16 at 15:19

Put it this way: there is a case on record of ball lightning rolling out of a fireplace, across a room and out the door. Brian Drummond's comment is spot on. The enormous current transients involved, with their associated electric and magnetic fields, can produce completely bizarre effects. For the most part, lightning strike effects can be handled effectively. I suspect that your PC has a good power supply, and there's a spark gap protector in there somewhere. If this is so, then you're seeing and hearing a successful protection incident.

Nonetheless, if this is a common occurrence, I strongly advise that you invest in an external surge/lightning protection unit, and not a cheap one. I well remember, twenty years ago, when I discovered that my phone was dead. After the line was repaired, I discovered that my modem was dead. Opening the case found it full of confetti, which was the innards of several capacitors. The capacitors had not handled the surge produced when lightning hit my phone line very well (which is why my phone line went dead, of course), but the modem did successfully protect my PC.


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