I'm fishing for ideas - lightening protection - Page 1
Forum section: electronics / projects

author: tkamiya
author_rank: Super Contributor
timestamp: June 16, 2020, 07:27:47 pm
content: As the title says, I'm fishing for ideas for lightening protection. Power source side is covered. Expanded ground system way beyond rules require, two layers of whole-house surge protector, and UPS.What I am concerned about is a cable TV/Internet connection. Where I am, coax comes to my cable modem, and cable modem requires power. Only protection I have here is coax is bonded to the house ground. I'd like more.It would be the best if I can convert copper coax to fiber optic line outside my house but that's beyond my control. Ethernet side, I can go from Ethernet to fiber and back to Ethernet. Then there is a concern of powering up those little things. If I connect it directly to the outlet, that's another path that needs to be protected.How would I isolate power? (120V in our area) Medical grade isolation transformer is the best I can come up with. Does anyone have ideas you can share? I am in Central Florida, the lightening capital of the United States.

author: Gyro
author_rank: Super Contributor
timestamp: June 16, 2020, 07:42:54 pm
content: I don't know how much it helps, but surge protection has become a key part of the IET 18th Edition Wiring Regs used in the UK. It includes things like site survey / geographical and other risk assessment (sounds like a no-brainer where you are!) and various degrees of protection, from Surge protection devices (SPDs) in the consumer unit (breaker box?), to additional bonded protection devices on telecom, antenna cables etc.Unfortunately the IET wiring regs (BS 7671) aren't freely available on-line, but if you do a search for 'IET 18th Edition' you should find lots of guides, explanations, videos etc. from equipment suppliers and other sources. Hopefully you will find some of it applicable, even though you're in the US.

author: tkamiya
author_rank: Super Contributor
timestamp: June 16, 2020, 08:40:49 pm
content: Unfortunately, in our area at least, "whole house protection" is not mandated or automatic. Power company will be glad to install one but they will charge monthly fee. I did my modification myself. (I am a licensed electrician) Also, reg calls for two ground rods and call it done. It's a joke!Glad situation is better in UK.In US, we are quite regulation heavy but they tend to miss what's really important.

author: Gyro
author_rank: Super Contributor
timestamp: June 16, 2020, 08:48:10 pm
content: QuoteWow!

author: tkamiya
author_rank: Super Contributor
timestamp: June 16, 2020, 08:56:36 pm
content: That was my first impression. Something like 10 dollars a month. It is a kind of unit that installs UNDER power usage meter. Takes 5 minutes to install, and the device not that expensive. They get revenue forever. Tampering with the meter is against the law, too.So I did it at the main circuit breaker which is my property and right next to the meter.

author: Gyro
author_rank: Super Contributor
timestamp: June 16, 2020, 09:06:37 pm
content: Actually, yes, that's where it's done in the UK (on the 18th edition anyway). The consumer unit directly off the meter tails so you own it (the SPD).

author: madires
author_rank: Super Contributor
timestamp: June 16, 2020, 09:19:53 pm
content: Quote from: tkamiya on June 16, 2020, 07:27:47 pmYou can buy surge protectors for cable TV. They have to be placed where the coax enters the house and they need to be grounded via the building's ground system.

author: tkamiya
author_rank: Super Contributor
timestamp: June 16, 2020, 09:21:29 pm
content: Yes, I know. It's already there. I'm looking for additional protection. Thank you for the reminder though.

author: engrguy42
author_rank: Frequent Contributor
timestamp: June 16, 2020, 09:26:55 pm
content: You can buy a coax surge protector, though I'm not sure how effective they are. Though there are some from big names like Siemens.As far as power can't you just get some MOV's? That's what the power company uses to clamp transients on their side. Just make sure they are decent MOV's with fast enough response (like a 1.2x50uSec lightning pulse or something like that).BTW, I'm curious if you've actually had bad stuff happen, or does FPL (?) do a decent job of protection. I'm just wondering if maybe it makes more sense just to buy a backup modem or something if it's that important.

author: Gregg
author_rank: Super Contributor
timestamp: June 16, 2020, 09:32:29 pm
content: Polyphaser has both surge suppressors and lightning protectors that fit your needs. You might be able to find what you want o fleabay.https://www.polyphaser.com/

author: tkamiya
author_rank: Super Contributor
timestamp: June 16, 2020, 11:54:17 pm
content: Quality of any type of lightening protection varies widely. I've taken few a part. Just a couple of MOV, MOV with inductor, and nothing at all. Coaxial type tends to depend on spark gap. By the time enough voltage builds up to jump the gap, the equipment is toast. By the way, MOV is no match for lightening induced transients. Some of them do good job against other appliances generating spikes.Yes, I've lost few things to lightening. At a different location, I lost half of an apartment full of appliances. At this location, few network ports, gateways, etc. Electrical power source is fairly robust. I have layers of protection, and in this area, wires are underground. Somehow, cable TV infrastructures are rather susceptible. That may change when fiber optic spreads to my area.Either way, I don't want to depend others doing the right thing. I do want my own protection which I can trust. I have a lot more to lose. Lab full of equipment and over a dozen computers all networked together.I forgot about Polyphaser. They are quite expensive but their reputation is next to none. Thank you for suggestion. Problem with this type though is ground connection. Good ground is on the other side of house, and code calls for ground entrance be done at one location only. To be effective, Polyphaser needs to be installed close to my modem with short low impedance ground. I'll figure this out. There got to be a way.

author: MarkF
author_rank: Super Contributor
timestamp: June 17, 2020, 12:09:59 am
content: I will put forth a resource (Mike Holt on the NEC) you can refer to:https://www.youtube.com/user/MikeHoltNEC/videosWhat I have gathered from his videos is that ALL the systems inside your house should be tied together.With ONE and only ONE connection to an outside ground.The goal is that you want to eliminated voltage differences inside by a lighting strike. If you have multiple outside ground rods, a lighting strike will create a voltage potential between them which will come inside and create a potential between systems inside.One example:I find these new GMOVs from Bourns very interesting:https://www.digikey.com/product-detail/en/bourns-inc/GMOV-20D111K/GMOV-20D111K-ND/10054803https://media.digikey.com/pdf/Data%20Sheets/Bourns%20PDFs/GMOV_Series_DS.pdf

author: engrguy42
author_rank: Frequent Contributor
timestamp: June 17, 2020, 12:11:22 am
content: Quote from: tkamiya on June 16, 2020, 11:54:17 pmNot sure why you say an MOV is no match for lightning induced transients. It's what your power company uses to protect zillions of $$ of equipment from lightning and other transients. There's probably one on the primary of the transformer on the pole feeding your house. They're designed to protect against lightning. There's a absolute crap-ton of stuff out there describing their use. For example, here's a nice paper from Littelfuse:https://m.littelfuse.com/~/media/electronics/product_catalogs/littelfuse_varistor_catalog.pdf.pdfBut hey, whatever you want to believe is up to you.

author: tkamiya
author_rank: Super Contributor
timestamp: June 17, 2020, 12:24:46 am
content: Referring to Mike Holt's web page.....Yes, that IS the reason why I said what I said. It goes something like this. You have two sides to the house. South (S) and North (N) for sake of easy conversation. Your electrical entrance is on S and your ground is S, and ground enters house from S. At the point, neutral wire is bonded (connected) to the ground.When lightening hits somewhere near S, ground potential rises. Neutral side of electrical outlet potential rises as well by the same mount. It's no longer at zero potential. It's elevated by quite a large amount. Then it propagates from there inside the house. In the mean time, the lightening energy spreads via ground separately. By the time it reaches N side, it's less. Ground is conductive but not as good as solid copper wire.Now, if you happen to have another ground rods on N side, potential will rise, according to the ground level at that point. Now, you have a problem. Your electrical wiring has risen by larger amount than N side ground. There is a difference in potential. Which will cause damage.This is why I'm being so careful. I could make situation worse by randomly burring grounding rods. One method to avoid this is to surround the house with thick ground wire and place grounding rod all around the house. But I can still only enter the house from one point.I didn't read about this on web. I do hold an electrician's license from Japan. I was professionally trained.

author: EEVblog
author_rank: Unknown
timestamp: June 17, 2020, 01:07:22 am
content: http://www.eatoncorp.com.au/ecm/idcplg%3FIdcService%3DGET_FILE%26allowInterrupt%3D1%26RevisionSelectionMethod%3DLatestReleased%26noSaveAs%3D0%26Rendition%3DPrimary%26dDocName%3DPCT_361252MOV's can be used in CAT B and CAT C locations.

author: sibeen
author_rank: Frequent Contributor
timestamp: June 17, 2020, 01:20:42 am
content: Another company you can look at is Transector which concentrates on Silicon Avalanche style suppression.https://www.transtector.com/Now, I'm going to be pedantic. The word islightning. Lightening has a completely different meaning,

author: tkamiya
author_rank: Super Contributor
timestamp: June 17, 2020, 01:43:18 am
content: That's my typing accent!

author: tkamiya
author_rank: Super Contributor
timestamp: June 17, 2020, 02:06:50 am
content: OK, folks. Thanks for the education.I still have issues with practical implementation in my environment.Currently, my thinking goes something like this. Move cable modem to side of the house near service entrance. That will provide low impedance ground, and access to main circuit breaker panel. (that alone solves grounding issue)Use Polyphaser (I trust the company and its products) CATV filter outside and make direct connection to the main ground. Cable enters the house there. There is also a sub panel. Add a circuit breaker and a whole house surge protector (MOV included) to feed the modem, and fiber optic network converter. From there, my network feed to switches is fiber optic only.That's a lot of work for a stupid internet connection! But I have a lot to lose.Somehow; though, if possible, I'd like to eliminate adding a circuit breaker. Maybe use one of the existing branch circuit and put a GOOD surge protection there to prevent back feeding of what gets through coax protection?

author: ejeffrey
author_rank: Super Contributor
timestamp: June 17, 2020, 02:33:34 am
content: Quote from: MarkF on June 17, 2020, 12:09:59 amNote that multiple ground rods can refer to two separate things. In the US you often need two ground rods but they are connected to the main panel in parallel and does not cause this problem. What you generally aren't supposed to do is add ground rods at subpanels which could allow ground potential differences and a large current flowing through the ground conductor.

author: tkamiya
author_rank: Super Contributor
timestamp: June 17, 2020, 02:54:37 am
content: Right. There is a strict rule about that.I have a few ground rods and they are daisy chained. Strictly speaking, this is not quite right. They need to be in star configuration. I couldn't do it any other way.I've heard of recent change in NEC where when A/C condenser unit is concerned, the ground can now be right near the unit. I have to read up on it first. Seem silly to me as my first opinion.I'm really waiting for copper to residence setup to become available in my area.

author: Gregg
author_rank: Super Contributor
timestamp: June 17, 2020, 09:43:45 pm
content: On a large data center in Silicon Valley I had a lightning rod system engineered by a specialty company. It consisted of lots of lightning rods and 11 ground rods all around the building; the lightning rod system was grounded separately from the other grounding system that consisted of many ground rods along three sides of the building all connected together by thermite welded bare copper buried cable finally terminated on a large bus bar in the electrical room. I have enclosed some drawings for reference. I also installed Polyphaser devices for all of the external security cameras.An array of lightning rods can also bleed off static charge and prevent some lightning strikes.For your house you might consider installing multiple ground rods all around, tie them all together externally and bring the ground wire in to an appropriate bus bar that will enable you to connect your other systems that require grounding as well as the house electrical system. With a ground ring around your house, you will provide a low impedance path for any near lightning strikes to dissipate with minimal impact to your house.

author: tkamiya
author_rank: Super Contributor
timestamp: June 17, 2020, 10:52:21 pm
content: Thank you for sharing that. I appreciate it very much.Thermite/CAD welding scares me, so I'll probably use clamps....

author: cdev
author_rank: Super Contributor
timestamp: June 18, 2020, 12:30:13 am
content: Although there are occasional lightning storms in Northern CA, they seem to bequiterare, at least in San Francisco and the North Coast. There are lots of torrential downpours, but not much lightning, compared to much of the rest of the country.

author: tkamiya
author_rank: Super Contributor
timestamp: June 18, 2020, 12:39:36 am
content: In a month or two, strong thunderstorm with torrential rain will be a daily occurrence. I almost drove right into a small tornado, too. New residents quickly learn, if weather looks bad, wait 15 minutes or so and it will clear.Once in a wide open part of a college, I was caught in light rain. I had an umbrella so I opened it. I started feeling tingly and I got a shock when I touched the metal shaft. I threw down the umbrella and took cover. Another time, we were taking cover under a canopy due to rain. Kabooon! Direct hit on tall building across the street. That was LOUD!

author: HackedFridgeMagnet
author_rank: Super Contributor
timestamp: June 18, 2020, 01:28:18 am
content: Are you just trying to protect against surges caused by a nearby strike or also against Direct Strike on your building?If it is just surges coming in on the comms line then as much inductance as your comms line can handle is your friend.Couple this with MOVs after the inductance as they will work faster than Spark gaps.For any inline inductance be careful of the magnetic material saturating as your inductance will disappear.Radio Isolators or optical would obviously also be good here.If you want direct strike it is much harder and costlier.From the franklin rods straight to earth in the most direct path, ie straight down.Low inductance cabling, flat alumnium tape is probably the most cost effective.You can probably buy thermite welded connections onto rebar if you look. I think you would only want this if you haven't poured the slab.

author: madires
author_rank: Super Contributor
timestamp: June 18, 2020, 10:02:59 am
content: Surge protectors for communication lines need to have a low capacitance, otherwise they would impact the high frequency signals on the copper wire. If you really want to use a MOV choose one with a low capacitance or hide its capacitance by a diode bridge. Usually you'll find GDTs (low capacitance anyway) and TVSs (hidden in diode bridge, and faster than a MOV).