Ethernet & Lightning

[chriscollins]

Hi all. A question for the collective. Every 5 or so years, we take a nasty lightning hit at the studio. Usually, it takes out a number of NIC's. Since they are on board, it causes me quite a pickle replacing motherboards in the automation system.

Has anyone tried any of the ethernet lightning devices? Any opinions?

I had three thoughts...

1. Put a NIC in each machine so it takes the hit.
2. Put a switch in each room, so it absorbs it.
3. Purchase the ethernet lightning protectors I found and put one on each end of the long, attic runs.

Opinions?

 

[OKCRadioGuy]

I'd put polyphasers on stuff going in and out of of your plant or super long runs....

 

[Kmagrill]

All ethernet devices are transformer coupled, which is a pretty good start. Perhaps the solution is to buy a bunch of $15 ethernet cards and just not use the integrated NICs. We have had ports fail on motherboards for no reason, but instead of trashing an otherwise good board or computer, we just toss one of those cheapie ethernet cards in and move the RJ45 to the new card. Takes 15 mins and costs $15.

 

[ChiefOperator]

The best form of protection, IMHO, is to prevent the surge from entering the building; thus, protection at the primary entry point. Yes, the polyphasers are quite good. I've also seen L-Coms at many sites.

The other poster's suggestion that you use additional NICs is interesting and probably a good idea to handle any sneak through current.

For POTS, beyond the usual devices, I've seen some of the Sandman CO line protectors work quite well. At one of my xmtr sites, the Sandman CO protector took one hell of a hit. Pretty much destroyed the protector, but prevented all damage downstream.

 

[TomT]

Grounding, grounding, grounding.

We have a co-located studio, the block building was built with chicken wire in the walls between the insulation and the sheet rock. The chicken wire was bounded to a peripheral copper cable which goes to ground stakes in the septic system leach field.

Also bound to this common ground is the AC panel ground, and shield grounds on the coaxes coming off the (225') tower. Larger incoming coax cables into the studio building go through Polyphasor pass-throughs ( UHf/VHF RPU antenna feeds, outgoing feed for 10 watt translator on our tower). RG-6 feeds--TV cable, satellite feeds from the LNB's--go through the "F" connector type grounding pass-throughs. All of the pass-throughs are mounted to a brass plate which is then connected to the common ground system.

Only thing we've lost to lightning in recent years have been tower lighting feed (up near the top of the tower) and a cable modem & switch (cable installer by-passed our grounding system when I was not around to watch what he was doing.)

OK--not easy to do in a rented building. At one site in a 3rd story loft we ran 3" strap from the equipment rack, across a roof, then down to a good ground in the alley along the back of the building. Worked well until new ownership disconnected. Ka-pow.

New station we bought moved to a split-level house. Studios in bedrooms above garage. Luckily garage ceiling unfinished--we ran copper strap between studios, equipment and AC panel, then out a window of the garage and into a water well on the 3 acre site. STL cable also bonded by copper strap to this ground.

A note about power company grounds--the ground for the incoming AC was a short copper grounding rod pounded in filled soil below the meter--but ABOVE the main panel in a hallway adjacent to the lower level garage. Don't buy this nonsense about the "only common ground allowed is power company ground." We have both clay soils and sand locally--get a dry summer and you better have multiple ground points, not just the inadequate grounds the power company uses.

 

[pellmell]

The idea of putting a $15 switch near the computer makes a lot of sense even with the other techniques mentioned here. With a plug-in NIC, a lightning strike can reach and destroy the motherboard. Been there, done that.

 

[Kmagrill]

Although I've never blown anything more than a NIC in a lightning strike, a sacraficial switch or hub may, indeed, be a really good idea. Be sure it is as close as possible to the critical computer(s).

On grounding, this is always a good idea, but it is often impossible to get a good ground. Fortunately, you don't actually need a good ground to protect your equipment. The main goal is to get all equipment bonded together so that no voltage differential appears between pieces of gear during a strike. In other words, your equipment is safe even if everything in the plant has 10,000V on it. The problems occur when one device has 5,000v induced on it when an adjacent device has 15,000v on it. Then electrons start flowing and stuff blows up. Bonding everything together with copper strap is a good start. Solder or weld the strap whenever possible, avoiding screws. Of course, if you can get a good ground, do that too. Every little bit helps.

 

[chriscollins]

Thanks all.

You seemed to have agreed with pretty much all three of my original thoughts.  The problem is the surge gets into those long, old CAT5 runs in the attic.

I am thinking of going the switch route.  I just want to protect my motherboards in my automation boxes.  I don't want to rebuild that system again for a while.  It's all identical hardware and it works great.

I'll just put a Gig Switch in each control room and keep two spares on the shelf.  Replacing a switch is easy.  Rebuilding an entire automation system is a PIA.

 

[westom]

You seemed to have agreed with pretty much all three of my original thoughts. The problem is the surge gets into those long, old CAT5 runs in the attic.

You have completely ignored what so many have posted. Due to inferior earthing, you have all but inviting surge currents to go hunting for earth via your electronics.

If a surge is incoming on a gigabit switch, then the same electric current is also outgoing destructively to an ethernet device. It is electricity. If the outgoing path does not exist, then the incoming path also does not exist.

Zero protection means keeping an inventory of spares for damage that does not happen when earthing is properly implemented. You had damage because the surge found a best connection to earth via your ethernet devices. So good that the surge even overwhelmed 2000 volt protection to take that better connection to earth. You have all but invited a surge to take that path due to no protection where it must always be implemented. Low impedance (ie 'less than 10 feet') to earth ground.

 

[SirRoxalot]

One thing to keep in mind if you're adding additional switches...

(5, 4, 3 Rule)

Between any two points on the network, the maximum number of Ethernet cable segments, each with a 100-meter diameter, is 5 (five).

Between any two points on the network, the maximum number of repeaters is 4 (four).

Between any two points on the network, only 3 (three) of the five cable segments can have network devices on them (other than repeaters), with the other segments serving only as inter-repeater links.

When counting the number of repeaters, count only the repeaters between any two points along the path on the network.

 

[chriscollins]

One thing to keep in mind if you're adding additional switches...

(5, 4, 3 Rule)

Between any two points on the network, the maximum number of Ethernet cable segments, each with a 100-meter diameter, is 5 (five).

Between any two points on the network, the maximum number of repeaters is 4 (four).

Between any two points on the network, only 3 (three) of the five cable segments can have network devices on them (other than repeaters), with the other segments serving only as inter-repeater links.

When counting the number of repeaters, count only the repeaters between any two points along the path on the network.

I'm homeruns on everything. Just introducing 1 repeater. I'm IT, not an engineer to the poster above this... I can't rework the grounding of the building. I just want to offer some protection to MY gear. You are also incorrect that a switch passes the surge. It takes it to ground and protects the devices on the other side.

 

[boiseengineer]

I bet lightning would go through an intermediate switch, take out what's connected to it, and blow it's plug/wall-wart (cheap) off the wall.

 

[TomT]

We had lightning take out a cable modem, then fry the switch. As I mentioned above--cable guy didn't ground his entry well, then just strung cable around the building and into the modem. Wasn't there for the install, didn't check it--then blam.

I re-routed the cable though a grounding block. Lightning will go wherever it can.

 

[boiseengineer]

After a lightning strike took out a guy wire and then dropped the tower, a corporate insurance person asked me how lightning would normally behave in that situation.
Reply was something like

Lightning will go wherever it can.

That incident was observed. All the insulators were lit-up constantly for over a minute. Sky stayed "purple". Top guy dropped and that was it! They located where the steel cable was burned in two at the top insulator.

 

[westom]

I'm IT, not an engineer to the poster above this... I can't rework the grounding of the building. I just want to offer some protection to MY gear.

Protection is earth ground. How many said it? Nobody said anything about receptacle grounds. You are an IT guy admittedly without basic electrical concepts. Your damage is traceable to your confusion. A ground, also required for human safety, is easily upgraded / corrected so that switches are not damaged. Easy as in layman skills required.

If grounding existed, then lightning should not damage switches. An entire building could have three wire receptacles or 1930 two wire receptacles. Does not matter. Protection is about a different ground where wires (and lightning) entered. A solution easily implemented even in 1930 wired buildings. Nobody said anything about rewiring the building.

Switches were damaged because a current is incoming on one cable and outgoing on another (ie into an ethernet appliance). Denying well understood concepts makes little sense when, by your own admission, you don’t know this stuff. A current powerful enough to overwhelm superior protection found in every ethernet port means grounds are missing are defective. Switches were damaged because lightning was all but invited to find earth destructively via the switch. What kind of current blows through ports rated at 2000 volts? A current that would not be inside the building had grounding been properly installed. A solution that might cost less than new switches – it may be that easy. If grounding is missing, then you have no protection. That simple.

 

[chriscollins]

I'm IT, not an engineer to the poster above this... I can't rework the grounding of the building. I just want to offer some protection to MY gear.

Protection is earth ground. How many said it? Nobody said anything about receptacle grounds. You are an IT guy admittedly without basic electrical concepts. Your damage is traceable to your confusion. A ground, also required for human safety, is easily upgraded / corrected so that switches are not damaged. Easy as in layman skills required.

If grounding existed, then lightning should not damage switches. An entire building could have three wire receptacles or 1930 two wire receptacles. Does not matter. Protection is about a different ground where wires (and lightning) entered. A solution easily implemented even in 1930 wired buildings. Nobody said anything about rewiring the building.

Switches were damaged because a current is incoming on one cable and outgoing on another (ie into an ethernet appliance). Denying well understood concepts makes little sense when, by your own admission, you don’t know this stuff. A current powerful enough to overwhelm superior protection found in every ethernet port means grounds are missing are defective. Switches were damaged because lightning was all but invited to find earth destructively via the switch. What kind of current blows through ports rated at 2000 volts? A current that would not be inside the building had grounding been properly installed. A solution that might cost less than new switches – it may be that easy. If grounding is missing, then you have no protection. That simple.

All I did was ask a question. I feel like you are the two post cops or something. While you may be knowledgeable. You apparently know very little about interpersonal communication.

 

[ChiefOperator]

Westom-

Regardless of your intention, your posts are coming across as somewhat rude. I realize that you're new to the board, so you may not realize the tone of your posts.

Many of us come from different backgrounds and ask questions. I'm an engineer, so I have a different perspective than chriscollens who is an IT guy and always offers help when asked.

The members of this board get along well and share alot of valuable information. Please join us and share your knowledge, but we ask that we all treat each other with respect.

Thanks, CO

 

[westom]

While you may be knowledgeable. You apparently know very little about interpersonal communication.

You admit to only being an IT guy. In the next sentence, you somehow know more than an engineer with decades of experience. Well, your denials explain why your switch damage exists. I should have been insulted when the admitted naive then know more. Instead, I addressed why you have damage. You denials say why you did not get it.

Destructive currents have all but been invited to find earth destructively via switches only because of what you have (or have not) done. That is not rude. That is the problem and solution.

Reason for switch damage: incoming on one cable. Outgoing destructively on another. Your switches obviously are not earthed. As so many said, your solutions are grounding, grounding, and grounding – which needs fixing to avoid future switch damage. That is not grounding the switch. What you read is not what so many recommended.

 

[TomT]

Let's ignore all this and go back to the beginning. This is a studio, right? Not a combined site (with the transmitter at the same location)?

Ignore the AC wiring for the moment and anything you know about IT and go back to the horse & buggy era. Remember seeing lightning rods on barns? Lightning likes to hit high, pointy things. Now go outside and look at the building.

First--any pointy things sticking up from above the roof line. Like an STL tower (or just a mast with the STL antenna). How is this connected to good old mother earth? Does the tower sit on a little concrete pad? Or do you have a mast attached on the roof of the building? You want some heavy metal (uh..we're talking about a different type of AC/DC here.....) connecting the tower into the soil, or from the mast down to ground, preferably to a couple of good ground rods.

Next, coaxial cables. The big ones (like 1/2 inch for the STL lines) need some special techniques to really ground them without damaging the cables or the equipment they are connected to; but a simple techniques is to use hose clamps and clamp grounding braid to the metal of the antenna connector (Source for grounding braid: http://www.surplussales.com/antennas/Antennas-11.html

The little coaxial cables like those used for your off-air antennas and tv cable (and cable modems--) can be run through grounding blocks like these in the pictures (Radio shack sells them): http://www.electronix.com/satellite-c-11.html

More to come--have to run...

 

[TomZ]

I was taught to avoid any braid and use single strand solid wire or flat copper.

When barns were protected with aluminum braid down the roof and to the ground and lightning struck them, they said that you would heat burns on the shingles when the braid turned into an inductor...

I never saw it but I believe it.