Lightening Question ??
Discussion
During recent heavy rainfall and bad weather up ere int North,
Our freeSat dish was struck by lightening, lightening tracked through coax
into ring main and killing everything that was plugged into the mains(and on standby).
It will never happen to me, but it did, lost tv's, dvd's, freeview box's, freesat box, telephones, router and even the PCB of the combi boiler.
I am familiar with working with electrickery, I checked all appliances fuses, all intact?? but DB trip tripped.
What I cannot get my head round is - is lightening carrying a voltage, a current or as a taxi driver suggested a frequency??
And yes we are insured and they are paying out..
Comments appreciated guys & galls
Our freeSat dish was struck by lightening, lightening tracked through coax
into ring main and killing everything that was plugged into the mains(and on standby).
It will never happen to me, but it did, lost tv's, dvd's, freeview box's, freesat box, telephones, router and even the PCB of the combi boiler.
I am familiar with working with electrickery, I checked all appliances fuses, all intact?? but DB trip tripped.
What I cannot get my head round is - is lightening carrying a voltage, a current or as a taxi driver suggested a frequency??
And yes we are insured and they are paying out..
Comments appreciated guys & galls
Simpo Two said:
Lightning makes things break/catch fire
Lightening just makes them lighter.
We like to have things right on this forum
Thanks for keeping me write, wright, right, Aaaagh, but you are right.Lightening just makes them lighter.
We like to have things right on this forum
Luckily nothing did catch fire, assume trip tripped before heat built up.
annoying and frustrating, damned lightning.....
more annoyed at self for not unplugging 'things'.
Lightning doesn't actually involve moving much charge, the damage is done by the rate of change.
It's a very high peak current attempting to pass through an apparently short bit or wiring, in a very short time. The voltage induced across that wire is all to do with the rate of change of current:
V = L.dI/dt.
Since the time is very short (single-figure microseconds) even though the instantaneous current is moderate (100 - 1000A) a meter or two of 'conducting wire of any thickness at 1microhenry a metre or so - results in very significant transient voltages appearing, easily enough to kill consumer electronics.
That's all there is to it, and since the causes are so fundamental in physical terms, there's really nothing you can do about it either. The best protection is to make structures that look likely to get hit.. have a low inductance to the Earth around the outside, a.k.a a Faraday cage; hence those flat, wide lighting 'tapes' you often see around the outside of most buildings (and which go to their own separate earth spikes).
It's a very high peak current attempting to pass through an apparently short bit or wiring, in a very short time. The voltage induced across that wire is all to do with the rate of change of current:
V = L.dI/dt.
Since the time is very short (single-figure microseconds) even though the instantaneous current is moderate (100 - 1000A) a meter or two of 'conducting wire of any thickness at 1microhenry a metre or so - results in very significant transient voltages appearing, easily enough to kill consumer electronics.
That's all there is to it, and since the causes are so fundamental in physical terms, there's really nothing you can do about it either. The best protection is to make structures that look likely to get hit.. have a low inductance to the Earth around the outside, a.k.a a Faraday cage; hence those flat, wide lighting 'tapes' you often see around the outside of most buildings (and which go to their own separate earth spikes).
To expand on Huff's explanation, the reason that these voltage spikes do so much damage it that fact that nearly all modern consumer electronics use switched mode power supplies (SMPS). These do not use transformers and there are semiconductors effectively connected to AC. Semiconductor junctions are extremely fast and guaranteed to fail millions of times faster than fuses.
Old style electronics used transformer power supplies. The iron cored transformer as well as reducing the AC voltage had the useful effect of filtering any fast voltage spikes on the AC input.
We had a major lightning strike here many years back and every piece of electronics that used an SMPS died. Everything that used a transformer type power supply survived without damage.
Today all our 'delicate' circuits (TV, sat, video, DVD etc) are protected by isolation transformers.
Old style electronics used transformer power supplies. The iron cored transformer as well as reducing the AC voltage had the useful effect of filtering any fast voltage spikes on the AC input.
We had a major lightning strike here many years back and every piece of electronics that used an SMPS died. Everything that used a transformer type power supply survived without damage.
Today all our 'delicate' circuits (TV, sat, video, DVD etc) are protected by isolation transformers.
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