I need to get a couple of mains blocks. I can get 4-way Belkin ones with surge protection (F9H400uk1M) for about £5.50 which is about a quid more than a normal block costs down the local B&Q.
I'm no electrician, part of me looks at the wave of £30+ surge protectors out there and thinks they're designed to look pretty and scare people out of their money, on the other hand I've had enough people bring their home PCs to me at work because their PCI modem's stopped working after a recent thunderstorm to think for the sake of a quid more on a mains block I might as well.
Anyway, looking around the belkin site there's all kinds of joule and amperage and db ratings and I'm curious what it all means?
I won't be connecting anything out of the ordinary, PC and bits to one, AV amp/sky/TV/DVD to the other.
It's be nice if any explanations could be "plain english", and not turn into a "whole house protection" argument as seems to happen on every thread I've seen on google!
And how is a mains surge arrestor going to stop a large pulse coming down the phone line. I, personally think they are all a waste of money, but you pays your money etc....
That's very easy. Just killfile w_tom, since his "advice" almost always pertains to Northern America and is completely incorrect for UK/Europe, despite his having been shown to be wrong on more than one occasion. Treat his advice as you would that from a double-glazing salesman sitting on your sofa - ask him which surge protector manufacturer he works for and watch him go quiet; his advice is clearly not at all impartial.
The "whole house" surge protection devices he constantly advocates for the Northern American market are totally irrelevant to our (UK) domestic installations, a point he seems unwilling or unable to grasp.
And there's plenty who'll take the money off them as wants to pay it. But especially here in the UK, neither grotty mains nor lightning strikes are common, and when they are the kind of penny-priced VDRs which "provide" the "surge protection" are b'all use...
e.g. a 69p Spike suppressor from Maplin is all you need to match most "spike suppressor" mains blocks.
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I'm no electrician, part of me looks at the wave of ?30+ surge protectors
Modems tend to get killed by spikes on the phone wire rather than the mains. You could try a couple of the above suppressors between each exchange wire and a ground point on your incoming telephone line.
Just an indication of the amount of energy that the suppressor can shunt before turning its toes up. In theory the bigger the better.
In plain english: spike supression for the computers is not going to do that much for you, although at 69p a pop you may as well do it. If you want any real protection then get a UPS. Never tried proctecting a phone line, so not sure how effective it will be.
A surge protector will 'stop' what kilometers of sky could not? Victims of ineffective protector myths (such as Mike Tomlinson) who promote these half truths. (Mike will reply with insults to prove his technical superiority).
It is routine to suffer direct strikes without damage even in regions that have more serious lightning storms. But the basic concepts must be understood. Plug-in protectors avoid all discussion about the most critical function in protection to sell their ineffective but so profitable products.
Scientists measure direct lightning strikes to a communication tower atop Hoher Peissenberg in Southern Germany. Why are those CMOS devices, rated only for tens of volts, not damaged by million volt lightning strikes? Simple They use the same concepts demonstrated by Franklin in 1752.
How effective protectors work is summarized in a previous discussion: "Pull the wall plug or not?" in nz.comp on 7 Sept 2004 at
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Do not confuse the protector with protection. They are separate devices of a protection system. A protector is only effective when connected short to protection. That protection is earth ground. An effective protector never stops, blocks, or absorbs surges. Concepts detailed in that previous discussion.
A surge protector is > And how is a mains surge arrestor going to stop a large pulse
Indeed it can. The cloud/lightning/cable/earth system forms a voltage divider: so long as the impedence from cable to ground is significantly lower than that of the lighning strike, then the voltage will be (relatively) low.
The main components of the impedence in the divider are:
- the resistance of the air to the strike. This is quite low once the arc is extablished.
- the resistance of any spark gaps to ground. Again, quite low once the arc is struck.
Power lines are equipped with arcing horns to encourage the ground arc to strike, so the peak spike voltage once the ground arc has struck is probably about twice the peak mains supply voltage.
There is a short period between the lightning strike and the ground arc striking when the voltage on the line can rise to many times the supply voltage.
Telephone lines don't have this protection, but they do have little green boxes with very small gaps between the connections inside, which also encourage arcs, and will certainly have surge suppressors somewhere, probably at the exchange.
From the strike point to the equipment to be zapped, the main impedence components are:
- The inductance of the cables
- The capacitiance of the cables to ground. These form a low-pass filter that will tend to spread out the energy pulse, reducing amplitude and rise/fall time and increasing duration.
Hence, fitting a surge suppressor (only) in a domestic situation will help if the strike is some distance away - the further the better. It won't help much is the strike is on the phone wires leading from your local pole to your house!
If you think that you're at real risk, you can buy commercial units (for rather more than 69p) which contain a spark gap, a series inductor and a parallel surge protector. These, if connected to a GOOD earth, will filter out all but the biggest surges. They are available for power, phone, TV aerial and data lines.
True, but these systems are designed with lightning strikes in mind.
These devices are NOT inneffective. The worst you can say is that their effectiveness is limited. There are limits to all forms of lightning protection. If lightning actually strikes your TV aerial or phone/mains incomer, then it is almost impossible to avoid some damage - even if it's only a zapped surge filter!
And? What is your point here? Engineers regularly monitor lightning strikes (and induced surges) on a wide range of systems, including mains supplies, transmitting & receiving masts, phone systems, water and gas distribution pipes
Most devices in transmitter output stages (and receiver input stages) are, in fact, rated at hundreds of volts, not tens, but I see the point! They are not damaged because the designers put in a LOT of effort to fit surge filtering and suppression between the semiconductors and the exposed bits of metal.
Active surge protectors are normally connected as shunts (i.e. between the cable to be protected and ground) and normally present a high resistance as long as the voltage across them does not exceed a particular threashold, after which they present a virtual short until the voltage drops back to almost zero. Hence, they need a series impedence (such as an inductor) to work repeatedly - if they are connected straight across the mains, they will short the incoming power to ground as well (for the current half-cycle, at least) and the current may well overheat them. As they are designed (usually) to fail short, this will probably blow the incoming supply fuse. Special devices are needed for telephone systems that have a switch-off voltage higher than the applied DC, otherwise they stay on for ever once triggered.
Very true. Earth connections must present not only a low DC resistance to ground but be capable of carrying more current than the protected cable and also present a low dynamic impedence. The latter requirement means that the earth connection should be as short and direct as possible. This tends to reduce the effectiveness of distribution-board protection where the protected appliances have an alternative path to ground, due to the relatively high dynamic impedence of most domestic earth wires. Hence 'protected' TVs, for instance, will often be damaged during a strike on the aerial by arcs developing between the chassis of the TV and any nearby earthed metal, such as central heating pipes.
As I said earlier, there is very little that you can do to protect against direct lightning strikes, but most surges are either induced spikes, where a strike on a pole causes a large voltage gradient down the pole and across the nearby earth, and this capacitively couples into the affected cabel, or mains switching transients. Despite the careful design of substation switches, you still get arcs when circuits are broken and the surges these produce can never be completely suppressed at source. These surges have a much higher source impedence and so can more easily be filtered and suppressed.
The worst design scenario is the nuclear emp, where you have to protect against pulses with a risetime of 50kV per millisecond - this edge is so fast that it often manages to couple itself round standard protection and fry sensitive electronics, even inside sealed metal boxes...
Look, I've worked in Africa, where storms are frequent and severe, and believe me, nothing stops even a near miss from buggering up anything connected to a long piece of wire in the vicinity of a ground strike.
In the end, opto isolators and line transformers for audio seemed to reduce but not eliminate returns, and replacing the opto panel was cheaper...
When I returned to the UK, I DID get struck by lightning. Took out the overhead phone line and reduced it to a smear of carbon across the road.
What went?
Well, the modem was toast, and the serial/parallel card it was plugged into. And the input side of the laser printer plugged into THAT. The lightning then jumped into the mains wiring and raced round the house. I lost the PSU on a laser printer, I lost a CMOS chip on a digital hi-fi turntable, and I lost the digital stuff on a TV - but it was old and went in the skip.
The high stuff survived, as did most of the computer.
The carpet got a bit burnt where some mains cables ran underneath and over it.
An unused aerial socket connected to nothing was blown to pieces and out of the wall, as was an unearthed mains socket some cowboy had wired in on two core cable.
In all it cots me about 300 quid to get everything fixed, including new second-hand TV.
The landlord got the cottage rewired on the insurance since he felt it was a good idea and argued that after a strike like that he wouldn't want to be responsible for its condition.
Surge arrestors are a complete waste of time. Every BT phone socket has one. They don't work against a direct strike, or even a near miss. They sort of work a bit when its vaguely in the area.
In general a near miss on my overhead power lines here, causes the RCD to trip.
The greatest danger to computers is a momentary loss of power as the mains goes off, followed by auto reconnect, followed by a second loss of power when the grid discovers the branch is still on the line etc.. If the computer is set to auto boot, that generally crashes the disk head JUST in the middle of the boot sector or close to it.
Lost two computers operating systems that way, one past all recovery.
Yes.. And what is on the mains side of most equipment?
Eitherer a whacking great transformer with plenty of (leakage) inductance and coupled into at least an RFI cap and usually a bloody big electrolytic....or a RFI circuit comprising er - would you believe series inductors and capacitors across, and to ground?
Presumably you wouldn't.
The spark gaoop and or varistors are teh only thing missing, BUT remember that youi DON'T jget kilovolt surges on teh mains as its is down convreted by a thwacking big transformer somewhere up your street. THAT is what has the surge proection in it, aand its built like a brick (or iron) shithouse.
You get a smaller surge. Easly enough to be taken care of by a bit of RFO filtering and/or teh regulation in teh PSU itself.
It isn't routne for anything to survive direct strikes except stuff specifically designed for it, which a 69p surge arrestor is not.
Howevr, unlike you guys, I have actually worked servicing kit in the worst storm area on earth. Southern Africa.
Yah well no fine. Limited to exploding just before teh rest of what they are conected to explodes.
No pluse that is tamed by a tuppeny ha'penny surge arerestor will even cause a modern PSU to blink. If the strike is near and big enough to trouble it, the surge arressor will be long gone.
There are limits to all forms of lightning
Indeed. But they tedn to blow open and pass te crap straight through.
Actuyally you use opto isolators. CMOS is totally and utterly vulnerable to even a few tens of volts pickup on lines in or near storms. Soldered in the chips enough times to tell you that fora fact.
If you want to use CMOS, so it in a metal grounded box with opto isolators on ALL inputs and outputs.
Transmitters may well be valves still. Valves take lightning strikes well,. being a sort of controlled lightning strike themselves :D
With a lot of complec protection even a strke on an antenna can be reduced to something the power stages can handle, but its damned expenisve, and only worth it if the call out fee to replace yet another blown head amp up a mast is too high.,..
Primary protection is not inside a building. 'Arcing horns' and other earthing devices outside building on utility lines are 'primary' protection for that building. 'Secondary' protection is an earthing device where utilities enter that building. Secondary protection demands that all utilities enter at a common location so as to be earthed by the single point earth ground (SPG).
A connection to earth ground must be short because wire impedance is high - when discussing transients. Earthing wire (from each utility wire to earth ground - sometimes via a surge protector) must be 3 meters or shorter so that wire impedance is minimized. That also means no sharp wire bends, etc because what is low resistance may also be high impedance to destructive transients. Wire impedance to earth ground must be minimized for effective protection - a concept that cannot be over emphasized.
In N America, customer premise telephone lines are routinely installed with secondary ('whole house') protection. Arc type protectors have been replaced by superior semiconductor based protectors. And again, this protector must make a less than 3 meter connection to SPG. A typical N American protector is shown (it is equivalent to a master socket but includes a protector):
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Equivalent products that may be installed on UK premise interfaces:
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It is completely wrong to cite 'surge filters'. Nothing filters a transient that travels kilometers through non-conductive air (and converts that air to plasma, for those who need be anal accurate). Protection has always been about making the lowest impedance connection to earth. Shunt so that the transient does not find a destructive connection to earth via household electronics. This is well proven, pre-WWII technology. This is protection from direct strikes to nearby wires - as has been demonstrated even in my own abode. Direct strike with no damage is routine if a human has learned well proven earthing concepts.
No reason for a direct strike to cause appliance damage if the incoming wire is properly earthed - either by direct earthing connection or via a properly sized protector. In the States, where lightning is a greater problem, such protection is quite effective. Protection is installed for direct lightning strikes since lightning is the typically destructive transient. Series inductors to prolong the life expectancy of a surge protector - if the protector was undersized. But that filter is rarely installed in serious protection because, instead, we install larger and properly sized protectors. For example, a minimally acceptable 'whole house' protector selling for about £22 is rated for 50,000 amps. Since a direct strike would be seeking many paths to earth ground, including via the utility 'primary' protector, then 50,000 amps is more than sufficient
- especially for the typical 18,000 amp direct strike. IOW we install effective protection by properly sizing the protector; not wasting good money on grossly undersized protectors such as in plug-in power strip and UPS protectors.
Shunt mode protectors do not blow line fuses or circuit breakers. The transient is for microseconds. It takes more than milliseconds to blow fuses or trip circuit breakers. When fuses / circuit breakers do trip, it is often due to follow-on currents created by a damaged appliance. Again, if the direct lightning strike causes surge protector failure, then a human has installed a grossly undersized protector. Protectors are installed for protection from direct lightning strikes (without protector damage) which is why protection from other transients is irrelevant.
Since plug-in protectors are not installed for the typically destructive transient, then the plug-in product is often undersized as well as overpriced. The manufacturer provides no dedicated connection to earth ground and avoids discussion of earthing. Why discuss the most critical component of a surge protection system if the product does not even provide that necessary connection? Plug-in protectors are grossly over priced (on the order of tens of times more per protected appliance) and do not even claim to provide protection from the typically destructive type of surge. Protection is about shunting to earth - which plug-in protectors do not even claim to accomplish.
A s> > A surge protector will 'stop' what kilometers of sky could
All electronic appliances have sufficient protection. Any protection that would work at the appliance is already inside that appliance (which again is why plug-in protector are not effective). Protection that assumes an incoming transient will be earthed before entering the building. If this was not true, then every telephone switching center, connected to overhead wires everywhere in town, must shutdown to protect the £million machine. BT does not do that. Why? BT earths every incoming wire. Therefore no damage. Protection is that routine and that effective when earthing is the protection.
When damage results from thunderstorms, the learned human then starts at the earthing system. Protection from direct lightning strikes is routine and well published. Unfortunately too many fail to learn reality and just keep repairing the equipment. We who acknowledge that lightning damage is directly traceable to human failure suffer direct lightning strikes without damage. Its called learning from your mistakes - earthing the incoming transient:
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Well I assert, from personal and broadcast experience spanning
Paul, those surge suppressors are rather pointless as a) computers and electronic power supplies have more effective protection built into them already, b) theyre not very useful against direct or indirect lightning strikes, c) lightning is a tiny risk that, if it does strike, you can do very little about, short of spending real money upfront.
They _are_ effective against surges caused by large dirty industrial loads, or small dirty loads running on small unfiltered private generators, but very few houses have either of those to deal with.
Youll get more joy spending your 69p on a cup of tea.
OK, why not...
that simply doesnt follow. 1 million volts divided by 10 is still death to anything it touches. Or divided by 100...
dont forget the wiring inductance to earth, which is the real killer to your voltage divider idea.
they do since 1930. Before then, people were killed occasionally by using the phone during a storm.
nope, white boxes with white gas discharge tubes, GDTs. PCB gaps went out with the passing of dial phones in the 80s.
this just doesnt logically follow. Run some numbers and see.
youre not, not in UK.
not really, lightning makes mince meat of everything it touches. It isnt going to take the slightest notice of the insulation on that inductor. Lightning makes whole wiring systems light up like christmas trees.
certainly not true in UK. If you do get hit, your entire eletrical system is toast, try and reuse it at your peril.
wrong again, could say much worse.
There isnt any hope of it being just a zapped surge filter, we're talking over a million volts. If it strikes anything on the house, its toast time. The insulation in domestic wiring and appliances means very little to lightning.
wrong again.
Those are passive surge protectors.
ah! correct.
Domestic CUs havent been called distribution-boards in a very long time.
often?
indeed, it can be done but is not worth the high expense. Such protection is more suited to commercial broadcasters and power utilities.
those arent a problem here, you dont need a little box to deal with them.
I suspect thats a non issue for domestic apps.
w_tom, if you put real numbers to your arguments, a few things would become clearer. And some of what you say simply doesnt line up with British practice.
Amen to that. Even better are power supplies fitted with a bizarre semi-autosensing-powersupply, which works out whether it's on 110V or
240V, and seems to select power transformer taps "appropriately". Brilliant design when a brownout on the 240V supply makes the thing decide it's moved across the Atlantic, and then the voltage comes back up to 240V after a few seconds...
Even yer green-CD-pen wound-by-virgins oriented-crystal oxygen-free-copper power conditioner won't help with that one!
I seem to have got under your skin. Good. Anything to counter the lies, slander, evasions, half-truths and distortion of facts that you post.
Your unique 'demented rant' posting style on a single subject simply makes it look like you have an axe to grind and allows you to avoid direct questions. If you want to appear at all credible, post in-line. The convention in uk.* is not to top-post:
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