Clamping voltage on surge protector?

[charles]

and - if it strikes your house when you are in the act of pulling them?

[Huge]

It's going to hurt.

[westom]

Described was a simple and well proven solution used in radio stations, telco switching centers, and even munitions dumps so that surges (including direct lightning strikes) do not cause damage. Quite a few here are posting denials based in feelings; not justified by any professional source, personal experience, or basic electrical concepts.

For example, an average lightning strike is about 20,000 amps. And is routinely made irrelevant by a properly connection to earth. Lightning can be as high as 100,000 amps. So rare that most here have probably never seen one. Meanwhile an IEEE paper in the late 1970s says what happens when a rare 100,000 amp lightning strike hits incoming AC wires. 40,000 typically goes to earth via the 'primary' protection system (including the earth ground for each transformer). Another 20,000 amps may go off to other connections. And 40,000 amps may be incoming to the nearby building. Why do professionals recommend at least 50,000 amps protector for 'secondary' protection? Numbers published by professionals define the problem.

Good luck finding even one responsible source (ie IEEE, NFPA, FAA, BS, ISO, etc) that makes that claim. ESE devices have long been cited by professional sources as, at best, unproven.

Nothing stops lightning. And yet that is what adjacent protectors or ESE devices must do.

In any facility that cannot have damage, protection has always been about connecting surges (such as lightning) harmlessly to earth. Lightning rods do that to protect structures. Dedicated ground wires or 'whole house' protector to utility wires does that to protect interio appliances. In every case, protection is always about making a more conductive and lower impedance connection to earth. Earth is where hundreds of thousands of joules harmlessly dissipate.

Devices that claim to block, absorb, or avert surges such as lightning (ie series mode filter, plug-in protectors, ESE devices, magic boxes that claim to convert tiny surges into useful energy) are bogus. As indicated by claims even contradicted or not supported by manufacturer specifications. Voting is useless. since an only useful recommendation says why with numbers. As found in professional papers and manufacturer specifications.

Telco switching centers all over the world use properly earthed 'whole house' protectors. Since that less expensive and superior solution is also proven by over 100 years os science and experience. Similar solutions also implemented in muntions dumps since explosions are unacceptable. No other device (not even ESE) have that credibility. Protection is and has been always about the quality of and connection to earth.

Should you want more, well, ask and be buried in professional citations and case studies. But then only a fewest here actually did this stuff. And have describes in siginifcant detail and numbers how and why those proven solutoins work.

The protector at 650 volts means it starts doing protection at 650 volts. If a surge current is larger, voltage on that protector increases to over 1000 volts (current, not voltage, is the relevant parameter). Eventually that voltage becomes so high that a protector fails catastrophically. How high might voltage go? That is why the 'whole house' protector starts at 50,000 amps. Another example of how to separate hearsay from experience. Experiences describes concepts with well proven numbers traceable to responsible sources.

[westom]

[Johny B Good]

W_Tom, I'm not quite sure what you're trying to put across with the tree and cow example. From the details you gave, cow showing post mortem signs that the electrocuting charge had passed between the fore and hindlegs whilst a mere 33 feet away from the ground strike point (the hapless tree), suggest the cow was either facing towards or away from the tree at the time and was killed by the potential gradient created by the lightning strike in the ground it was standing on[1].

There is video evidence[2] of this effect exemplified by half the players on a sodden football pitch being stunned by a direct hit to the metalwork of the grandstand creating perhaps a kilovolt or more per metre voltage gradient on the pitch.

Any players who happened to have both feet in contact with the ground would have suffered an electric shock varying in intensity which depended not only how far they were from the (effective) entry point of the lightning strike but also their orientation and the seperation distance of their feet.

Those lucky enough to have both feet out of contact at the critical moment would have felt nothing, others who happened to have just one foot in ground contact would have experienced a lesser electric shock through that foot which would have also varied according to orientation and distance from the strike point.

[1] Possibly a 'ground leader' but most likely due to Ground Current or "Step Potential" as quoted from the wiki article here (second paragraph):

[2] Surprisingly, I can't track this video down. It seems to have been 'pulled' despite there being no fatalities in this case. My memory of the video suggests it was the second non-fatal incident reported here:

[westom]

No harmful gradient from a field existed as many assume with a term 'induced surge'. Had a cow been on the other side of that tree, then current would not have flowed up its hind legs and down its fore legs.

Destructive current had to be incoming on one path and outgoing on another. Induced transients (E-M gradients) do not cause damage or death. Actual current from a lightning strike must pass through (with an incoming and outgoing path) to cause damage. Damage is defijned by where current flows.

Another example. A nearby lightning strike hit l0 meters from a long wire antenna. Thousands of volts appear on that antenna's lead. Connect a NE-2 glow lamp (a milliamp lamp) to that antenna lead. The resulting current is so tiny as to barely cause that light to glow. And voltage drops from thousands to tens of volts.

Many see thousands of volts to assume a nearby surge is destrutive. Conduct a millimap or less to make that induced surge completely irrelevant. Induces surges are that easily eliminated. Simplest protection in all electronics means no damage from nearby strikes. To have damage means the item is part of that surge current path. That defines both an incoming and outgoing current path.

Farmers encircle barns with a buried ground loop. So that current from a lightning strike passes around the barn; not destructively through animals inside. Protection is always about where current flows; or does not flow.

Your wikipedia citation is discussing a lightning bolt - the plasma 'wire'. We are discussing what actually does damage - an electrical current. Simultaneous current is same in the 'direct' lightning bolt and 'indirect' bolt. Relevent here is that actual electrical current. Either current is created by a nearby, induced or indirect surge (generated by electromagnetic fields). Or a current is what flows directly from cloud to distant charnges. Latter is the current that causes hardware damage.

Earth a protector so that the current does not flow incoming and outgoing through any appliance. Then nearby strikes (with massive E-M fields) cause no damage.

[PeterC]

I wonder if cattle are as susceptible as horses. Quite recently there was a case of a racehorse killed by a mains leak underground. That would have been a much lower voltage gradient than a lightning strike, but apparently horses are far more sensitive to this than are human beings.

[tony sayer]

We _must_ have W_Tom back again as no farmer in England would do anything to protect their cows like that!..

All in its just a very simple shunt job to shunt the lightning discharge around what it is you need to protect. Use a low resistance and as low INDUCTANCE a path as possible and thats more or less that..

That bit re lightning charge dissipation came from a handbook provided by Messers Furse of Nottingham who have been making lightning protection systems for use world-wide for some 120 odd years now!..

[Huge]

If you're going to be an uber-pedant, you need to format, spell and punctuate your postings correctly.

[Graham.]

That would be a low *impeadence* path then.

[Uncle Peter]

It must have been a very small part of the strike, as only the network card died. Now if the network card can save the motherboard, why can't a surge protector?

[Uncle Peter]

te:

Well every single time I've seen a PSU's bulk caps explode because of do= uble voltage input, the 5A fuse in the IEC lead has blown.

-- =

Everybody is ignorant, only on different subjects.

[Uncle Peter]

Do a rave dance.

[Uncle Peter]

It'll protect the smaller ones. You might as well say why wear a seatbelt? I mean it won't protect you when you slam at 70mph into an oncoming lorry.

[meow2222]

funny

NT

[tony sayer]

In article , Graham. scribeth thus

To be sure soir!! it would indeed;)...

[Uncle Peter]

Well my dad's network card protected his computer from a smaller one. You do understand that there isn't just one main lightning bolt don't you?

[Uncle Peter]

As long as only the UPS fails.

[westom]

In one venue, milk production was serous down. Eventually, the problem was traced to bad grounding in the barn. Currents through aarth, that a human with shoes would not feel, was so harming clows as to cause (if I remember) a 20% reduction in milk.

Had humans been walking bare foot, I suspect they too may have felt it.

[harryagain]

You get a nearby strike and everthing is blown to bits. I had one where the phone line was reduced to a black mark on the wall. the local pole transformer was buggered . Incoming mains cable had the insulation melted. Fortunately I saw the storm approaching and turned the mains off and unplugged phones. I still have pix somewhere of it approaching, I'll see if I can find them.