elecrical safety during thunderstorms


Postby laburnam » Fri Mar 11, 2011 11:14 am

Please could someone help me as I am getting conflicting advice. During a thunderstorm I know to unplug appliances.

I also unplug my television aerial cable but I do not know what to do with the unplugged end. Do I leave it lying on the floor or put it next to something metal to help it go to earth, or what (on earth - pardon the pun) should I do with it ?
Thank you so much for any answers. Regards Caz
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Postby ericmark » Sat Mar 12, 2011 12:31 am

Most aerial sockets have a decoupling capacitor so you will not get a shock from the aerial.

The advice I was given as a radio ham was never to earth the aerial. This is because electricity will find easy route and you don't want to make your aerial into a lighting conductor.

Aerials should not be installed on earthed items like soot encrusted chimneys or on sharp edges like the gable end of a house. As this would increase the likeliness of a direct strike.

However it is considered in the UK that we don't have enough thunder storms to worry about the problem of a strike.

During an electric storm we have a potential difference generated and it does not need a direct hit to take out electronic equipment. Most equipment damaged by a storm is not due to direct hit.

Using a pre-amp to boost signals normally means that is the item which fails rather than the TV. Often the VCR or Sky box gets it first as they are first in line so very unusual for a TV to go down.

Where the supply is from overhead lines there is a chance that a storm will produce spikes on the line which can cause damage. However it is rare. In the main the best option is insurance as of course you may not be home when lighting strikes.

If you live in the USA then maybe you need to take prosecutions for lighting. However in UK only where silly amounts of metal are put into the air like with radio hams do we really need any special prosecutions.

But do not earth the aerial cable. You may fix a very large resistance between the cable and earth to leak away voltages after the storm and even include a spark gap. This is done with the phone line entering the house but never seem it done with TV. Again maybe a radio ham would do this. The problem is with a radio ham or CB guy they do not have de-coupling capacitors in the wall socket so unless there is a path to earth then they can get a nasty belt off the cable. But most TV plates do have de-coupling capacitors put there to stop you getting a belt as you plug in the aerial in high winds.

With a de-coupling capacitor in the wall plate even if you did earth cable it would not earth aerial anyway.
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Postby laburnam » Sat Mar 12, 2011 10:40 am

Hi there eric - thank you so much for your reply. You are very knowledgeable. My Dad was a radio ham and I remember the enormous aerial we had in the back garden.
I can't say I understood everything you said - it's a bit technical.
However, my TV aerial is on the roof of my house and the aerial cable just comes into my front room through a samll hole in the wall rather than being in a socket. So when I unplug the aerial from the TV the aerial cable is my front room loose and I don't know what I should do with it.
Do I leave it on the floor - it's a concrete floor with carpet on top. I have been told that if I leave it lying on the floor and lightning struck the aerial then the electricity would fly around the room looking for somewhere to earth itself!!! What should I do with this unplugged aerial cable ? Thank you for your time. Caz.
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Postby ericmark » Sun Mar 13, 2011 10:35 pm

What you want is a "Braid-breaker" these are designed for TVi but will also offer protection so you will not get a belt from the aerial lead when plugging it in.

Do not correct the aerial lead to earth the cable will not take the 1000A likely to flow with a lighting strike and would attract the lighting the same as any other lighting conductor on a building.
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