How does lightning affect appliances with no Earthing?

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It is not very uncommon for appliances to be affected when lightning strikes nearby. This mainly occurs because there is a tendency for the lightning to travel up the earthing wire, thereby damaging the appliance through a high power surge (at least that's what I had learnt).

Some days back, during a thunderstorm in Kolkata, lightning struck near our apartment. Although none of our appliances were damaged (because all three pin appliances have stabilisers which have lightning surge protection on Earth wire), many of our neighbours have been affected. And the most interesting fact is that, all appliances that were affected, were of two pin, like mobile chargers and mobiles connected to chargers.

When we had visited Cherapunjee in Meghalaya, India, we had faced something like this. Cherapunjee is a place that gets very heavy rainfall. In our guest house, there was a light holder with a bulb, which couldn't be lit from the room (the switch was not working as per the staff). However, whenever lightning was striking outside, the bulb was lighting up. It shows that lightning was somehow affecting the bulb, even though it didn't have an Earth connection.

Can you explain these phenomena?
 

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  • #3
Dale
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It seems like you think that a two pin power outlet is not connected to ground. That is not correct. The neutral wire is grounded.
 
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Rive
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Was that bulb connected to a dimmer?
 
  • #7
Rive
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No, not at all.
If it was not some electronic 'bulb' like LED or similar, and it was also not connected to/through a dimmer (or some other electronic switch), then I would say something there was (most likely) not up to code there.
 
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It seems like you think that a two pin power outlet is not connected to ground. That is not correct. The neutral wire is grounded.
You've answered the first question.

Soon after your post, I went down and looked into my neighbour's main fuse box. A fuse box generally has two fuses - one on live, and the other on neutral. But this person has put a very very thick wire in the fuse of both neutral and live. As a result, a part of the lightning could easily travel up without damaging the fuse, and damaged the appliances.

It also shows why this person often suffers from burning of appliances' core due to high current instead of the fuse blowing and saving the appliance.
 
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Dale
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But this person has put a very very thick wire in the fuse of both neutral and live
This is a very bad idea. It is a code violation in most places and puts everyone in the building at increased risk of fire.
 
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This is a very bad idea. It is a code violation in most places and puts everyone in the building at increased risk of fire.
True. But no one can say anything to this person. He is a retired engineer, and now he considers himself having knowledge in everything: physics, chemistry, electronics and even medicine! You'll have to live with such people in apartments.

There is only one way: changing the fuse myself when he is not at home. :wink:
 
  • #11
russ_watters
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It seems like you think that a two pin power outlet is not connected to ground. That is not correct. The neutral wire is grounded.
...and lightning is not so selective in its target: it can hit the hot wires. Heck, many transmission lines don't even have neutral/ground: they are three-phase, all hot. The ground/neutral for single phase is derived at the transformer.
 
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  • #12
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...and lightning is not so selective in its target: it can hit the hot wires. Heck, many transmission lines don't even have neutral/ground: they are three-phase, all hot. The ground/neutral for single phase is derived at thectransformer.
It seems to have traveled up the neutral, because lightning struck within 1km radius of our apartment.
 
  • #13
davenn
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It is not very uncommon for appliances to be affected when lightning strikes nearby. This mainly occurs because there is a tendency for the lightning to travel up the earthing wire, thereby damaging the appliance through a high power surge (at least that's what I had learnt).

that isn't correct ... any earthed wire will more likely carry the current to Earth (ground) rather than back into equipment ( that happens to have an earth)

It seems to have traveled up the neutral, because lightning struck within 1km radius of our apartment.

and that is also a bad assumption

As Russ stated just prior to your last comment ...

...and lightning is not so selective in its target: it can hit the hot wires. Heck, many transmission lines don't even have neutral/ground: they are three-phase, all hot. The ground/neutral for single phase is derived at the transformer.


Lightning will travel through whatever path it has available to try and reach earth/ground. If there is no Earth connection, then it will just blow the crap out of whatever it encounters as the energy is dissipated ( caveat ... It will still damage electronics/electrical stuff regardless of if there is a connected Earth or not)

Dave
 
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  • #14
Rive
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that isn't correct ... any earthed wire will more likely carry the current to Earth (ground) rather than back into equipment ( that happens to have an earth)
The Earth/Ground/Neutral wires/connections are usually not rated to those currents involved in close lightning strikes. It happens that a close lightning strike elevates the local neutral potential (together with the Earth there) to unusual levels (compared to, for example to the reference level of a phone/internet/cableTV line).

Ps.: I believe originally it is called something like 'step potential', but it is just hopelessly messed up by all those wires around, so instead of one circular potential field around an unlucky tree now we have a few dozen such areas in unlucky households around any unlucky utility pole...
 

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