dslreports logo
 
    All Forums Hot Topics Gallery
spc
uniqs
34

ChillyCat6
join:2004-09-07
Chesterland, OH

ChillyCat6 to handlebar

Member

to handlebar

Re: lightning protection

MYTH: A surge protector or UPS device will provide sufficient protection against all lightning strikes, including a direct lightning strike.

TRUTH: Unfortunately not. A common surge protector will stop voltage spikes and surges, but not the violent, catastrophic burst of current from a close lightning strike. Direct lightning current is simply too big to protect with a little electronic device inside a power strip, or even a hefty UPS unit. If your UPS or surge protector is in the way of the lightning's path, all or part of the lightning will just flash over or through the device - regardless of the amount of capacitors and battery banks involved.

Even 'disconnects', or devices that physically switch off power to a device by activating a set of contacts, will not guarantee protection. A small air gap will not stop a lightning bolt that has already jumped across miles of air. It won't think twice about jumping a few more inches, or even a few more feet, especially if the 'path of least resistance' to ground is across the contacts of the disconnect switch.

Not only that, but not even a full-fledged lightning protection system with rods, cables and grounds will guarantee against damage to electronics and computers. For any system to provide 100% protection, it must divert almost 100% of the lightning current from a direct strike, which is nearly physically impossible: Ohm's Law states that for a set of resistances connected in parallel, the current will be distributed across ALL resistances, at levels inversely proportional to the different values of resistance. A house or building is nothing more than a set of resistors 'connected' in parallel- the electrical wiring, plumbing, phone lines, steel framework, etc. (Even though plumbing and electrical wiring, for instance, may not be physically connected, lightning will use side flashes across air gaps to effectively connect them). In a direct lightning strike, the current will not follow only one path- it will distribute itself across all paths to ground depending on each path's resistance.

Lightning current often peaks at 100,000 or more Amperes. With that in mind, consider if you have a lightning protection system installed, and your house is hit directly by lightning. If the protection system takes even 99.9% of the current, then your electrical wiring may take the remaining 0.1%. 0.1% of 100,000 Amperes is a 100 Amp surge through your lines- which may be enough to take out your computer.

It is not uncommon for 'side flashes' to occur inside a house or building, where all or a part of the lightning will jump across an entire room to reach ground- such as from the electrical wiring system to well-grounded water pipes. If your computer is in the way, it'll be time to shop for a new one, even if you have the most expensive protection system installed.

A 'side flash' often occurs when lightning branches out into several channels as it tries to bury itself deep into earth. So even if the bulk of the current is flowing to ground through the heavy cables of your protection system, there can be small 'overflow' disharges, even if the lightning hits outside of the structure. Such an event was experienced by my Grandmother, who witnessed a 6-foot long blue spark jump across the room from a wall outlet to the kitchen faucet as lightning struck nearby.

Guarantees on the packaging of UPS/surge protection devices are somewhat misleading when it comes to lightning protection, implying that the devices can stop any effects of a strike. In some cases, they will - as long as they aren't in or near the direct line of fire. But in reality, nothing can guarantee absolute protection from a direct or very close strike.

All this doesn't mean that you shouldn't use a surge protector, UPS, disconnect, or a full-fledged lightning rod system. Any device will provide some degree of protection from everyday power line spikes and distant lightning strikes. But when lightning hits nearby or directly, all bets are off.

The best, and cheapest, way to protect your stereo, television, computer, or any electronic appliance is to unplug all power, telephone (modem), and antenna connections during a thunderstorm.
handlebar
join:2011-02-25
Grover, NC

handlebar

Member

said by ChillyCat6:

Not only that, but not even a full-fledged lightning protection system with rods, cables and grounds will guarantee against damage to electronics and computers. For any system to provide 100% protection, it must divert almost 100% of the lightning current from a direct strike, which is nearly physically impossible: Ohm's Law states that for a set of resistances connected in parallel, the current will be distributed across ALL resistances, at levels inversely proportional to the different values of resistance.

Lightning current often peaks at 100,000 or more Amperes. With that in mind, consider if you have a lightning protection system installed, and your house is hit directly by lightning. If the protection system takes even 99.9% of the current, then your electrical wiring may take the remaining 0.1%. 0.1% of 100,000 Amperes is a 100 Amp surge through your lines- which may be enough to take out your computer.

It is not uncommon for 'side flashes' to occur inside a house or building, where all or a part of the lightning will jump across an entire room to reach ground- such as from the electrical wiring system to well-grounded water pipes.

All this doesn't mean that you shouldn't use a surge protector, UPS, disconnect, or a full-fledged lightning rod system. Any device will provide some degree of protection from everyday power line spikes and distant lightning strikes. But when lightning hits nearby or directly, all bets are off.

The best, and cheapest, way to protect your stereo, television, computer, or any electronic appliance is to unplug all power, telephone (modem), and antenna connections during a thunderstorm.

I believe it's usually the ground surge that wipes out cattle and computers. Contrary to the electrical code, Bellsouth often put their service entrance 30 feet from the power entrance and didn't bond the grounds.

When I saw the situation I bonded my electrodes. In 1998, lightning hit a tree 30 feet from my electrical service entrance. I was online at the time. It knocked out my phone service, but the bonding and surge protector prevented damage to my computer equipment. About 2002, lightning lit the neighborhood orange when it struck a tree 60 feet from my service entrance. It blew bark 40 feet. I was online. No electrical damage.

In 2005, I was online when my house got hit. Masonry from both chimneys was blown a long away. Lightning blew a hole in the roof and knocked off siding. It wrecked perhaps $2000 worth of electronics, including a stereo receiver that wasn't hooked up or plugged in. My CRT was left with colors all over from the intense electrical field. However, none of my computer stuff was damaged. There's a case where equipment plugged into a surge protector fared better than a disconnected receiver.

I was online in 2010 when my house got hit again. I may have had $1000 worth of electronics wrecked, but none of my computer stuff. Both times my house got hit, there had been no lightning or thunder within 30 miles. It wasn't stormy and the sky wasn't ominously dark. There was no warning for me to unplug things.

A thousand miles from here, I was running through the living room in a thunderstorm when lightning jumped from the ceiling light to the floor, in arm's reach in front of me. Upstairs, my sister screamed. Lightning had come from the ceiling and hit the brass bed she was in.

Decades later, she moved into a farmhouse. Popping and blown bulbs were routine in thunderstorms. I solved it by bonding.

I'm glad the cable is bonded to the power ground at the service entrance, but in a storm there could be instants when, at the modem end, the cable could be thousands of volts different from the power circuitry at that point. It seems to me that a surge protector could absorb that energy. It might be thousands of amps, but it should be brief, not thousands of joules.
westom
join:2009-03-15

2 edits

westom

Member

said by handlebar:

It seems to me that a surge protector could absorb that energy. It might be thousands of amps, but it should be brief, not thousands of joules.

No surge protector absorbs that energy. View its numbers. Protectors are hundreds of joules. Destructive surges are hundreds of thousands of joules. No protector works by blocking or absorbing surges. Protectors are only connecting devices. Either a protector connects hundreds of thousands of joules harmlessly to your single point earth ground (ie phone line and AC electric ground now bonded into one big earth ground). Or that protector does nothing useful.

You have assumes a surge automatically destroys everything. It does not. A surge inside the building goes hunting. It selectively destroys appliances that make a better connection to earth. Protection is always about connecting every single wire inside every incoming cable to the same earth ground. So that surge energy is not even inside a building. That is why earthing is so critical.

One AC electric wire connects directly. Other two must be connected via a 'whole house' protector. Telephone already has a 'whole house' protector installed for free. But yours was ineffective when not connected to a 'single point ground'. Uniting both into one big ground created single point ground.

No protector does protection. Protection is always defined by the quality of earthing. Where all energy is harmlessly absorbed. Some wires (ie cable) need no protector - connect directly to earth. But in every case, either the protector makes that low impedance (ie 'less than 10 foot') connection to earth. Or that protector is ineffective. Bonding short to earth is critical.

Appliances already contain protection equal to or better than anything that might be on its power cord. The computer had some protection with or without an adjacent protector. Which appliances connect surge current better to earth? Those are the damaged appliances. Protection inside other appliances (ie GFCI, dimmer switch, digital clock) was probably more than sufficient because they were not the better connection to earth.

Bonding is important. But bonding must connect to every incoming wire. Either directly or via a 'whole house' protector.

Same applies to lighting rods. Many will argue point verse blunt. They miss the point. What is true for protectors is also true for lightning rods. Only as effective as what does the actual protection - earth ground. You may also want to upgrade earthing for those rods.