Let's talk lightning damage!

[JoeR]

I live in the lightning capital of the U.S... Central Florida. I have had lightning damage before, but never like this. Let me give some background and details. Maybe someone can tell me what happened.

I have two power runs that cover some distance. One goes from the house to a metal building 250' away. Another run goes to the front gate 800' away.

At the front gate I have an intercom that shares the phone line from the house with a surge arrestor bypass swith located at the house. I have a B/W video camera with RG-6 at the front gate.

In the house I have structured wiring, and all the phone, data, and video comes into one box. I use 66 blocks for the telephone, and 110 blocks for the data.

In the main panel, I have a surge arrestor for the power line that shunts after 175V surge. Little green light indicates if it has blown or not.

On Wednesday, lightning struck within a mile of the house, but did not hit the house. It knocked the power off for about an hour. When the power returned I had the following damage:

Computer modem inoperative, senses no dial tone when tone exists. It is on UPS with phone surge protection.

Network card on another computer dead.

Front gate intercom doesn't ring house but can forward a call. (I suspect surge from phone line since modem and this device now have problems)

Camera not working but has power. (Power surge?)

My neighbor across the street had his alarm system wiped out, and his thermostat. (Power and phone surge?)

Other neighbor lost one of two cameras located in the barn and his 200amp main breaker to his house tripped.(Power surge?)


This Sunday, no storms and our phone lines go dead (I suspect the damage finally caught up to the main phone system). All of us on the street lost our phones. My gate opener and intercom stop working. I find the 18V AC transformer and the 16V AC transformer are both dead! I put an ohm meter on the power input legs and find them open on both transformers.

So, what happened? Did I get a power surge or telephone surge? If it was from the power line, why didn't that stupid 175V surge arrestor work?

This is aggravating!

Thanks,

Joe

[twstanley]

I have had to replace modems and motherboards for my father and for the in-laws after thunderstorms. Both of them had the phone line routed thru a "surge" protector which didn't seem to help a bit.

I don't think the phone surge protection helps at all, I don't know what method is used in them to protect modems but the ones I have experience with are worthless.

It sounds to me like you had a phone and power surge, I am not familiar with the 175 volt breaker you are talking about, if you had normal 240 volt service, I guess you could have that 175 volt breaker on one leg of that service. You very well could have had a 174.9 surge on both 120 volt legs of your service which could do a lot of damage without tripping the 175 volt breaker.

Your phone line could also have had a voltage surge which could easily fry your modem, pass thru the motherboard into the network card and go thru the network cable and fry your other network card ... possibly.

As far as the phone system and your transformers failing a day later, some of it could have been weakened and failed or a lightning strike could have hit out of earshot but still sent a surge on that day as well.

Lightning has immense power, the only thing you can do try and make sure you have lots of grounding capacity at your eletrical service entrance and phone entrance.

[Pat]

EMP is Electromagnetic Pulse. Lightning has more than one mode of attack. A direct hit will overvolt AND over amp just about anything.

Fairly near misses with no direct conducting path INDUCE voltage and current spikes. Lightning strikes have extremely high currents and fairly fast rise times. The faster the rise time the more widespread are the frequencies contained in the pulse. (see Fourier analysis)

Heard of the GEMP (Giant Electromagnetic Pulse) associated with large thermonuclear weapons? Same basic physics with lightning minus the radioactivity. Here is what happens...

A powerful lightning discharge will induce strong voltages in nearby conductors (phone lines, power wires, fences, metal gutters, and on and on. The lightning acts like the primary of a transformer and all nearby conductors act like secondary windings. The powerful electtromagnetic pulse induces corresponding powerful voltage spikes in conductors.

Surge protectors need to be capable of handling large differential mode (hot wire with respect to neutral or hot to ground or neutral to ground) voltage spikes. The protection device should also protect against common mode spikes where all the incoming conductors rise in voltage together (in common). Don't think this is safe like a bird on a high voltage wire is safe, tain't so.

The capacitance of your electronic device (TV, computer, etc) will allow common mode spikes to (well...) spike you. Differential mode is easier (cheaper) to protect. A MOV (Metal Oxide Varistor) is placed across each pairing of input lines (hot, neutral, ground). This is three MOV's. The MOV breaks down to a low resistance value when its voltage rating is exceeded thus providing a low resistance path to dissapate the spike. The MOV device recovers quickly and so doesn't short out the power wires permanently. Unfortunately each spike above the threshold value for the MOV takes a bite out of its capacity to take a licking and keep on ticking, i.e they "wear out."

You can buy large MOV devices from an electrical supply house and wire them up in your breaker box and get some protection for everything in the house. I recommend you also buy only good quality surge protectors for use on individual devices (in addition to the big MOV's in the breaker box.)

The cost of all these MOV devices would probably be well under the cost of recovering from a hit like you took.

There is no ULTIMATE protection scheme for equipment connected to the commercial grid or phone lines. Even with the largest MOV devices that will fit in your breaker box there can always be a large enough lightning strike to eat the MOV and toast your equipment. Unplugging (not just turning off) the equipment is very effective but makes using the equipment problamatical. Fiber optic likes are not directly bothered by lightning.

Caution: More folks are killed each year in the U.S. by lightning getting them through a corded phone than by being bitten by poisonous snakes and EVERYONE tries to avoid poisonous snakes.

A true story...that relates to unplugging electronic equipment and getting lightning damage anyway.

For a couple years I did field service work on large ($10 million per copy) tuna boats...radio, radar, sonar, etc. One boat came in to port after taking a near miss from a large lightning strike with virtually all its electronic gear smoked (12 VDC equipment) All of the crew were wearing digital watches on their wrists when the lightning hit near the boat. ALL OF THEIR WATCHES WERE FRIED! This is an example of EMP.

Hope this either helped with understanding lightning protection or at least cured a few folks with insomnia.

[img]/forums/images/icons/smile.gif[/img] [img]/forums/images/icons/smile.gif[/img] Pat [img]/forums/images/icons/smile.gif[/img] [img]/forums/images/icons/smile.gif[/img]

[JoeR]

Thanks Pat and twstanley.

Pat, do you recommend any particular surge arrestors for the breaker panel? Clearly, the one I have is not doing the job... Or as twstanley said, my surge was 174.9 volts! Now that would be my luck! [img]/forums/images/icons/smile.gif[/img] hahahaa!

Thanks,

Joe

[Pat]

JoeR, Except for "ringing", lightning induced surges are brief and transitory in nature. If your surge arrestor had been in service for quite some time in a surge prone area, perhaps it had been "used up." A lightning induced surge of a voltage below the threshold for a MOV sized for surge arrestor service would probably NOT cause harm to any properly designed consumer Devices.

I don't recall specific brands and it is unlikely that any given electrical supply house will stock an assortment of brands. I buy and take pot luck. If they don't have a large enough unit to make you comfortable, be advised you can connect multiple units in parallel for higher capabilities.

[img]/forums/images/icons/smile.gif[/img] Pat [img]/forums/images/icons/smile.gif[/img]

[Chuck52]

Lightning damages, but is also apparently sometimes heals! I have a detached building with its own small panel. This place was built in the 50's and I think the panel is original. About two years ago my brother visited and brought his big cab-over camper. He wanted to hook up to electric so he could use the airconditioner in his camper at night. I first plugged him into an outlet in the shed, since it was the closest grounded plug. Of course the old breaker tripped. It's probably a 15A, but is so old I can't read its capacity. After that, the light switch and single outlet in that part of the shed didn't work. The breaker seemed to reset, and I never got around to testing the juice at the switch because I seldom use the light involved. Last night we had a close strike. Don't know where it hit and I have no obvious damage at my place, but this morning the light was on in the shed. I guess I left the switch in the on position last time I tried it. I bet the breaker has bad contacts and the surge was just enough to make the contact. The light switch works fine now, but I haven't tested the outlet. Probably out to change out that old breaker. It might be fried closed!

Chuck

[Pat]

Chuck, I would not be surprised at all if the breakers contacts were welded together. Changing it out could be a significant safety improvement.

Two older ladies were in a hardware store and one was buying a 15 amp fuse for her old style fuse box when her friend interrupted to interject that she should buy the 30 amp fuse instead because you get twice as much amps for the same price.

[img]/forums/images/icons/smile.gif[/img] Pat [img]/forums/images/icons/smile.gif[/img]

[Chuck52]

But...but...but....Pat, If it's welded closed ain't I getting free electricle?

Chuck

[GaryM]

It's not only free...but maybe more than you need! [img]/forums/images/icons/grin.gif[/img]

[BlueRidge]

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<font color="blue"> Chuck, I would not be surprised at all if the breakers contacts were welded together. Changing it out could be a significant safety improvement.
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Yup. I'd be checking on that post haste!

BTW, excellent post on lightning, Pat. Most folks just don't understand how powerful that stuff is. A colleague of mine went to work for SprintPCS when they were new, and his first assignment was to create specs for lightning protection for their cell sites. So, first thing he had to do was to study up on lighting. He told me that what he learned about its power shocked him. (no pun intended, but a pretty good one anyway [img]/forums/images/icons/wink.gif[/img] )

Lightning releases more energy around the globe every 24 hours than is contained in all the nuclear arsenals of the world put together. I read that somewhere at the height of the cold war.