Lets see now. Now suppose lightning hits your TV aerial thats right next to the hi-fi and you might have an FM aerial and tuner on that.
Now just -how- does a "plug in" surge suppresser protect that?...
To protect a house against direct lightning strikes you need lightning rods, which would have to be designed to prevent strikes to the TV aerial. (Proper lightning rod installation includes other protection, such as a surge suppressor at the consumer unit.) Fortunately the probability of lightning hitting a house is very low in almost anywhere in the US. It is probably a lot lower in the UK. Elsewhere in the thread I said the likely maximum current coming in on a power wire was 10,000A. The average probabililty of a more severe event (including a direct lightning strike to the house) in the US is once in 8,000 years. (This comes from another technical paper from the author of the NIST guide.)
Ham radio operators protect their equipment from direct lightning strikes to an antenna, but the protection is far more elaborate than the rest of us would want to implement. Someone with a TV aerial on a very high mast might want to consider it.
You can do what you want.
I have 2 plug-in suppressors. Only an idiot would have 50. I have read a number of accounts of suppressors protecting what is connected to them while other equipment is damaged. Both the IEEE and NIST guides, written by experts in surge protection, have plug-in suppressors as among the effective protection techniques.
still missing the point then
They are effective against the type of surges that dont normally need protection against, but not lightning strikes.
They not reliable on a direct lightning strike to your house, a very unlikely event.
A plug-in suppressor with high ratings, wired correctly, has a high probability of protecting connected equipment from a very near lightning strike - for example to the utility pole behind your house with typical overhead power distribution. As detailed previously, the energy that reaches the suppressor in that near worst case event is surprisingly small. The NIST guide says "we will look at ways of protecting your appliances [including entertainment electronics] against lightning surges that come by way of the wires - power, telephone, cable, etc."
Using all the suggestions in the guides increases protection:
- good earthing
- clamping the voltage on phone and power wires to an earth connection where the wires enter the building, cable shield connected to earth;
*short* wires from each of these entry devices to a common connection (this includes a surge suppressor at the consumer unit)- plug-in suppressors on expensive particularly vulnerable devices, particularly those connected to both power and phone/cable.
That is basically what both guides, written by experts at surge protection, say.
You have your own experts?
I think tom was right about you
NT
Yes but how many have that?. Here in the UK its almost unheard of..
Never seen that done even on communications sites which are expected to have problems with strikes..
Perhaps not worth bothering with then?..
Perhaps the experts might need to revise their wibblings?..
One hit per 8000 yrs is about a risk of 1 in 2000 per 4 year life of a computer. 1/2000 of =A3250+=A3100 for a system is risk value of about 17.5 pence.
NT
Very rare in the US also - that is the whole point. You specifically asked about a direct lightning strike to an aerial. It is so rare (in almost all cases) it is not worth protecting against.
Lightning rod installation in the US is covered by "UL780". Surge protection of the incoming power wires is a feature of that standard. The lightning rod system must also be bonded to other earthing systems at the building, in particular the power system. Even with bonding, the down conductors can be far from the potential of other wiring.
If lightning hits a lightning rod, it travels to earth through earthing electrodes. That will cause the earth potential at the building to rise far above "absolute" earth potential. That can lift the building "ground" far away from the power wires - the same as a surge coming in on power wires (same for phone and cable).
What I wrote above is specifically about lightning hitting a building - in response to your question about lightning hitting an aerial. I don't think worrying about a direct lightning strike to a building is worth worrying about, but it was your question.
Now you are changing the subject.
You (and apparently NT) are confusing protection from a direct lightning strike to a building (your question) with surges (produced by lightning strikes) that come in on power, phone and cable wires. I have no idea about where you live, but where I live that is a risk.
In addition you can have other surges, particularly from normal and abnormal utility switching. That is also a risk where I live, but far less than lightning related.
The IEEE guide was written by 5 electrical engineers who actually work on surge protection. The IEEE is, I believe, the largest association of electrical and electronic engineers in the world. The guide "was written to make the information developed by the [IEEE Surge Protection Devices Committee] more accessible to electricians, architects, technicians, and electrical engineers who were not protection specialists." I'll bet neither you or NT have read it.
There is no need for the experts to revise what they wrote.
not a bit, but its a good excuse.
NT
In article > Perhaps the experts might need to revise their wibblings?..
Cambridge UK England..
Well perhaps the power grid out there is a bit different from ours.
Most all of our urban services are under-grounded here and quite a few out in sub urban areas. Its getting more the norm in rural areas wherever possible..
We just don't seem that keen ion masses of overhead wires anymore..
Oddly enough yes, but in practice we have a lot of equipment around but just don't bother with power surge arrestors across power lines and can honestly say its not been a problem.
Direct lightning strikes on RF towers another matter for which there are good lightning protection systems already in place..
A friend of mine who'd spent some 30 odd years in the domestic TV trade tells me that he's only ever known Three lightning hits on domestic premises in that time, and in two of those was actual damage caused which was mainly structural!..
Well lots of experts write a lot of things don't they;?..
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