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Lightning Strike To Antenna


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#1 bellotv

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Posted 31 August 2011 - 09:54 PM

Direct hit to antenna. Balan split open and internals vaporized.Balan boot split off.

6 meters of coax from antenna to a "$70 Crest " power board then fly lead to TV

The power switch was blown off the power board

The Samsung TV survived :D

http://www.dtvforum....t...st&id=12121

#2 Tazzy2Heads

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Posted 31 August 2011 - 11:03 PM

Direct hit to antenna. Balan split open and internals vaporized.Balan boot split off.

6 meters of coax from antenna to a "$70 Crest " power board then fly lead to TV

The power switch was blown off the power board

The Samsung TV survived :D

http://www.dtvforum....t...st&id=12121

Hi 'bellotv'
Sounds impressive !! I always wondered about a surge protector and a lightning HIT. Was the antenna earthed by chance ? They should get there 240V house earthing and main earth checked out if that's how the current went to earth ?
Cheers Tazzy.

#3 DrP

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Posted 01 September 2011 - 05:39 AM

Lightning is such an unpredicatble beast. I've seen cases where nearby strikes have written off heavily protected TX equipment; a strike just out side the front door of a building (chunk missing from paving) caused a small telephone system to essentially explode; while a building strike has left a PC power supply fully operational but popped the lids off chips on the motherboard.

#4 beeblebrox

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Posted 01 September 2011 - 08:34 AM

No fire?? So very often they result in a little/large fire too!!!

last one I did, it blew the antenna off the rafter mount, broke a bunch of roof tiles, went into the ceiling blew a four foot hole through the plaster and left a scorch mark on the floor tiles about 2 feet wide!!!

oh and it vapourised ever bit of coax wherever it had a bend in it, fused wallplates and destroyed 6 out of the 7 tv's in the house.

As for corona effect I've electronics stuff 100mtrs away from a direct hit get fried, we did a mansion a while ago that lost half the electronics in the house because of one.

#5 Tazzy2Heads

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Posted 01 September 2011 - 06:04 PM

No fire?? So very often they result in a little/large fire too!!!

last one I did, it blew the antenna off the rafter mount, broke a bunch of roof tiles, went into the ceiling blew a four foot hole through the plaster and left a scorch mark on the floor tiles about 2 feet wide!!!

oh and it vapourised ever bit of coax wherever it had a bend in it, fused wallplates and destroyed 6 out of the 7 tv's in the house.

As for corona effect I've electronics stuff 100mtrs away from a direct hit get fried, we did a mansion a while ago that lost half the electronics in the house because of one.


Hi 'beeblebrox'

Thats one hell of a BAAANG !! , Were they home at the time ?

When people ask me to stop a million or two volts in the last 6 or so metres from hitting their antenna with a little earth wire, I ask them where do you want me to SEND IT !
Cheers Tazzy.

#6 beeblebrox

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Posted 01 September 2011 - 07:04 PM

yes and needless to say had some washing of pants to do when they had calmed down!!!

When it comes to earthing I normally tell them all the electronics in their house isn't worth as much as what it costs to put in proper lightening protection. then I suggest they keep their contents insurance up to date!: )
especially here in Melbourne where we get so infrequent electrical storms.

#7 JK200SX

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Posted 03 September 2011 - 12:14 AM

So, out of curiosity, where the propereties/ or the antennas at a much high elevation than any other like object in the immediate neighbourhood? or just random?

#8 beeblebrox

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Posted 03 September 2011 - 08:03 PM

So, out of curiosity, where the propereties/ or the antennas at a much high elevation than any other like object in the immediate neighbourhood? or just random?

normally very random. I've only ever had one telescopic (30ft) mast hit and that was in a valley in coburg... they are normally in flat fairly treeless suburbs, the last couple have been epping, tarneit, caroline springs and wantirna.

Edited by beeblebrox, 03 September 2011 - 08:04 PM.


#9 bellotv

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Posted 03 September 2011 - 08:49 PM

So, out of curiosity, where the propereties/ or the antennas at a much high elevation than any other like object in the immediate neighbourhood? or just random?

The one in the OP was on a small knoll with trees around of similar height but was about 150m down a slop from a much higher hill with a house on it.

I've seen similar events again with vaporized balans and blasted coax like Beeblebrox said where there are bends in it.

from memory these were on low sides of the street.Perhaps houses on the high side also suffered ?. I don't know.

Also in nearly every case the phone lines were also seriously destroyed.One I remember burnt a hole through the carpet.There was a water pipe below it under the house.

Definitely crazy unpredictable stuff.

I've seen a telstra pit that was a molten blob of copper and the concrete cover was found about 100m away in a paddock

#10 JK200SX

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Posted 03 September 2011 - 11:41 PM

The other thing I forgot to ask in my post 3 above was that were the antennasystems grounded? I suppose what I'm trying to establish here is if the earthing would make the lightening strike more susceptible because of the direct path available?

Thanks,

JK

#11 westom

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Posted 04 September 2011 - 12:14 AM

I suppose what I'm trying to establish here is if the earthing would make the lightening strike more susceptible because of the direct path available?

Lightning will strike no matter what you do. Appreciate why. Lightning is an electrical connection from a cloud to earthborne charges maybe five kilometers away. The shortest electrical path is maybe three km down to earth and another four km through earth to those charges. What will stop that? Nothing.

Being the highest point does not necessarily mean more lightning strikes. Geology is a key factor. More often a mountain side rather than its top is struck. Just as often, lightning strikes down in a streambed rather than atop an adjacent mountain. It is always about the shortest electrical path.

Lightning would strike a FL home repeatedly on one wall. So they had lightning rods installed. Lightning again struck that wall. Those who do not always learn reasons why (before making conclusions) will then assume lightning is capricious. Not so. In that case, the bathroom wall contained plumbing that connected to deeper and more conductive earth. Lighting rods were connected to eight foot ground rods only in sand. Solution (as usual) was to improve an insufficient earthing.

Protection is always about what does the protection. That is neither a lightning rod nor a surge protector. Protection is defined by the quality of earthing electrodes and its connection. Protection from lightning is so routine that damage is considered a human failure. When surge damage happens, the scientific human learns where the human mistake was made. That analysis always starts with the earth ground. Where hundreds of thousands of joules must harmlessly dissipate.

When it comes to protection of a building, the lightning rod is only as effective as its earth ground. When it comes to protection of appliances, the protector is only as effective as its earth ground. Surges are never stopped. Protection means a surge is connected / diverted / shunted / switched / bonded / conducted harmlessly to earth. Geology is important for understanding why some locations have more frequent surges.

Edited by westom, 04 September 2011 - 04:30 AM.


#12 M'bozo

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Posted 04 September 2011 - 05:33 AM

Personally, I've seen widespread electrical/electronic damage to consumer items caused when 22kV overhead drops onto the distribution mains below, either from trees falling on lines, or motor vehicles impacting service poles.

Imo, surge protected power boards aren't much cop with this sort of event.

(I've also seen damage caused by "brownouts", usually the result of a dropped phase.)

Edited by M'bozo, 04 September 2011 - 05:54 AM.


#13 bellotv

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Posted 04 September 2011 - 08:41 PM

The other thing I forgot to ask in my post 3 above was that were the antennasystems grounded? I suppose what I'm trying to establish here is if the earthing would make the lightening strike more susceptible because of the direct path available?

Thanks,

JK

In all my cases antenna was not earthed.
Personally I think its a waste of time earthing for lightning protection in a domestic installation.It's just not practical or economic to do it effectively.

EG
Our local Community FM station has one of it's transmitters on a Comms site on a hill that is in a fairly high lightning area.

For lightning protection ,all equipment is bonded to an earth system that comprises of copper wire around 12mm in diameter that is trenched into the ground in a radial pattern for many tens of meters to dissipate a strike into the ground.

Several years ago a severe strike to the site vaporized the earth system and it had to be replaced .I am unsure of whether equipment survived or not.

You have to wonder how far do you go to protect yourself .

Westom,
you seem quite knowledgeable about lightning protection and would appreciate anything you can offer on this .
Thanks Bellotv

Edited by bellotv, 04 September 2011 - 08:45 PM.


#14 westom

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Posted 04 September 2011 - 11:29 PM

In all my cases antenna was not earthed.


In every case, lightning protection is about the current path to earth. Lightning (and other typically destructive surges) are a current source. Voltage will increase as necessary to blow through to earth. Millimeter gaps in switches and circuit breakers will not stop it. 2 centimeter parts inside power boards are mostly for show. Protection has always meant that current gets to earth by never entering the building.

Appliances are damaged because that current had both an incoming and outgoing path to earth. Both conductors must exist. If a surge has an imcoming path and no outgoing path; then no damage exists. A surge does not enter on a phone line, damage a modem, and stop. From basic electricity as taught in primary school science. Both incoming and outgoing current paths must exist to have damage.

All appliances already contain serious protection that makes most 'so called' surges into noise. Be most concerned about an event, typically once every seven years, that might overwhelm protection inside appliances. Every wire that enters a building must first be connected short to earth. For coax type cables (ie satellite dish, cable TV, TV antenna), a ground block and wire can make that short as possible (ie 'less than 3 meter) connection. For wires that cannot be connected directly (ie AC electric, telephone), a protector makes that short as possible connection.

A connection must be short as possible, with no sharp wire bends, no splices, not inside metallic conduit, separated from other non-grounding wires, etc to make that low impedance connection.

Telstra connects to buildings all over town. Its CO may suffer 100 surges with each thunderstorm. That switching computer must never suffer damage. So Telstra connects every single wire inside every incoming cable, short, via a protector, to single point earth ground. Then energy is absorbed harmlessly outside. No switching computer damage.

To increase that protection, telcos all over the world also want that protector separated from electronics. A less than 50 meter separation increases protection.

Obviously, protectors adjacent to electronics do the same near nothing that the manufacturer numeric specifications say it will do. Protector is typically too small, too close, and no short connection to earth,

Some other example of how protection was achieved even in forbidding environments. Ufer grounds were pioneered to protect munitions dumps from direct lightning strikes. A building designed using same concepts so that current need not be inside destructively:
http://scott-inc.com/html/ufer.htm

A Nebraska radio station suffered repeated damage because (in part) engineers disconnected grounds. In this case study, the secondary protection system (ie building earthing) is restored and upgraded. And the primary protection system (utility ground) was upgraded. Protection is about layers. Each layer is defined by the only item that must always exist in every protection layer - single point earth ground:
http://www.copper.or...y/nebraska.html

Entire solution was earthing; how a surge connects to earth so that current need not be destructively inside a building.

Edited by westom, 04 September 2011 - 11:33 PM.


#15 James T Kirk

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Posted 05 September 2011 - 09:34 AM

Hello Westom

A thought on lightning protection at broadcast facilities.

I believe the importance of equipotential bonding within a building cannot be overstated. Obviously the technical earthing system to which this connects is vital however if this low impedance bonding (@500kHz) is not present no amount of good earthing will protect from lightning damage. I read from your wording that you are aware of this with references to how cables are to be run.

In broadcasting facilities the technical earth is the most important earth in terms of lightning protection with the utility earth performing the same role as in any structure with supply through statutary compliance. In broadcast facilities, utility earthing in terms of lightning protection is generally more of problem than providing assistance.
Significant efforts are made to route these 25-100kA strike currents safely to ground external of the building, however having a 200 metre tall mast or tower with 150mm copper feeders entering into the building is a complication that is difficult to avoid, hence equipotential bonding within the building.

Very fortunately, broadcast facility technical earths by all measures are superior to utility earthing.

James

Edited by James T Kirk, 05 September 2011 - 09:42 AM.


#16 DaMasTa

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Posted 05 September 2011 - 03:47 PM

I believe the importance of equipotential bonding within a building cannot be overstated.


Gaa, big words .. >.< what does it mean ??

I know in most of europe it's law that every tv system must have an earth and isolated at the wallplate.

Probably isn't the perfect solution to protect against lightning, but i reccon it would help =] Pity we don't have this in our Aussie standards (or at least almost no one earths and uses isolated plates)

#17 viewer

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Posted 05 September 2011 - 04:38 PM

I'm a bit like DaMasTa.....can all that be explained (where possible) in laymans terms, and what is good or bad to do in the standard household to protect from lightning strikes?

Thanks for the info so far.

#18 beeblebrox

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Posted 05 September 2011 - 06:38 PM

The reality is in a domestic situation the cost of properly doing it far outweighs the benefit... what's your insurance excess for a lightening strike... sure it's not several thousand dollars...

In a commercial situation broadcast towers, telco exchanges etc sure it makes sense to a point. Even then how many times do we see thesse protected environments loose some services after a lightening strike!

#19 bellotv

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Posted 05 September 2011 - 07:03 PM

I know in most of europe it's law that every tv system must have an earth and isolated at the wallplate.

Hi DaMasTa
Do you know what this consists of in a practical sense.?IE the hardware involved in earth a typical antenna ,(earth cable sizes,stake ??? equipotential bonding to supply earth ?)

Is it more to do with lightning protection or keeping the antenna at ground potential from an electrical safety point of view ?

Beeblebrox ,have to agree

Edited by bellotv, 05 September 2011 - 07:05 PM.


#20 CMatten

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Posted 05 September 2011 - 08:26 PM

The reality is in a domestic situation the cost of properly doing it far outweighs the benefit... what's your insurance excess for a lightening strike... sure it's not several thousand dollars...

In a commercial situation broadcast towers, telco exchanges etc sure it makes sense to a point. Even then how many times do we see thesse protected environments loose some services after a lightening strike!


+1, I had a direct strike to my house a few years ago, all TV's / Video's and one DVD were replaced. I paid $400 (From memory that is my excess), the NRMA paid the other $11K.

#21 James T Kirk

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Posted 05 September 2011 - 09:08 PM

Gaa, big words .. >.< what does it mean ??

I know in most of europe it's law that every tv system must have an earth and isolated at the wallplate.

Probably isn't the perfect solution to protect against lightning, but i reccon it would help =] Pity we don't have this in our Aussie standards (or at least almost no one earths and uses isolated plates)


Sorry
Not meaning to make it sound complicated, it's just that as others have noted, this is a difficult area to get right because it is only proven correct over time.

Equipotential bonding, re lightning:
When a property is struck by lightning it is possible that the earthing system is momentarily elevated by several thousand volts. Equipotential bonding is the earth commoning of all equipment such that during the strike all the equipment within that building are momentarily elevated to this higher voltage as one. If there's no voltage difference between equipment they are protected. When you add the complication of cabling to equipment within a building to services outside the building like phone and power, this cabling has surge diversion to the earth commoning to keep voltages on these external sources to within the safe limits.

In a home installation it is likely that the mains earth or cold water pipe, depending on how it's plumbed from the road to the home are the best earths. The mains earth, even if connected to it's own ground electrode is still bonded to the home's cold water pipe somewhere near the breaker board. When I applied what I have learned over the years at work to my home I did the following:

(Note in my case the mains earth electrode and cold water are bonded at the breaker box)
(1) Installed coaxial surge diversion (F connector type) between the antenna and the splitter and bonded its earth to a nearby cold water pipe.
(2) Had mains surge suppression installed at the breaker box.
(3) Installed gas and MOV surge diversion on telephone line as close as possible to the building entry and earth bonded to a nearby cold water pipe.

Time will tell how successful this is. We have suffered very close lightning strikes such that the purity of the lounge and rumpus TV sets and the PC monitors were very marred (green/red screens), three or four efforts at degaussing were required to restore normal tube divergence, all equipment survived to date.

Realistically for antenna installers there are many points where surges can impact a building that you simply have no control over. As you know, the roof and gutter are isolated from the antenna cable by the balun in some cases, some times not depending on impedance matching technique used. If you were to always assume not and install coax surge diversion between the antenna and the socket or splitter and properly bond the surge diversion to the best available earth, your best effort genuinely has been achieved. You cannot be expected to sort the vulnerabilities created by other services

James

#22 westom

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Posted 05 September 2011 - 11:46 PM

The reality is in a domestic situation the cost of properly doing it far outweighs the benefit... what's your insurance excess for a lightening strike... sure it's not several thousand dollars...

Connecting every wire in every incoming cable to single point ground (to make equipotential) is about $1 per protected appliance. That installation means protection remains functional for decades. Protectors and earth ground must remain intact after every direct lightning strike. Why would anyone assume that is expensive?

In some venues, a cold water pipe is used. In places where code has been upgraded, even the cold water pipe is insufficient due to lead solder joints, sharp pipe bends, and often that pipe is too far away. Earthing means the connection must be short (ie 'less than 3 meters'). The ground wire must be separate from other non-ground wires. No sharp bends. Obviously a wall receptacle safety ground can not perform earthing for three reasons. That connection to earth must have no sharp wire bends, not inside metallic conduit, etc to make a low impedance connection.

High impedance means a surge current creates a high voltage. Low impedance means the same current creates a near zero voltage. If a high voltage is created, then a surge will simply go hunting inside the house. Will select the appliance it wants to connect to earth. Protection for over 100 years has been that simple.

In some facilities, to get just a little better earthing, means spending $thousands more. Most of the protection in any building is about earthing electrodes best located as close as possible to where all utility wires enter a building.

BTW, lightning is not capricious. The 'after damage' analysis will often determine why damage was traceable to human failure. Either that current is earthed before it enters a building. Or your only protection is that already inside appliances. An event they may occur once every seven years is either harmlessly earthed. Or hunts for earth destructively via appliances.

In Australia, AC electric protectors are available from Clipsal and ABB. A protector to earth phone wires can be obtained from Novaris. In every case, a dedicated wire exists for making that short as possible connection to earth.

Edited by westom, 05 September 2011 - 11:47 PM.


#23 DaMasTa

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Posted 06 September 2011 - 12:35 AM

Do you know what this consists of in a practical sense.?IE the hardware involved in earth a typical antenna ,(earth cable sizes,stake ??? equipotential bonding to supply earth ?)

Is it more to do with lightning protection or keeping the antenna at ground potential from an electrical safety point of view ?


bello, the wallplate is made differently, instead of a barrel type straight through like we have, they have some circuitry in them.

as to how they earth, i'm not sure the what standard the europeans have for earthing, but most splitters etc i noticed have an earthing point, i read that every system in italy must be earthed. i think it's more from a safety perspective, but i'm sure it would help at least a little bit for lightning protection. their tv industry is standardised too, kinda like a plumber is here, they have to go to trade school and everything.

i noticed some powered device we plug into the antenna network leak voltage up the line, i know a few times i felt a jolt on the coax, put a multimeter on it and measured over 100v .. lol .. mind you it didn have much current, but i was thinkin that if i plugged in like 10 devices it could get dangerous, that's just me thinkin tho, i dunno how dangerous it actually is. but i guess it makes sense to have an isolated wallplate.

#24 M'bozo

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Posted 06 September 2011 - 01:57 AM

In the interest of maintaining correct and proper information on this forum, posters may wish to google "westom lightning" to see similar discussions.

#25 James T Kirk

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Posted 06 September 2011 - 10:14 PM

Protection for over 100 years has been that simple.

BTW, lightning is not capricious.


Hi Westom

I find need to register some surprise at a few of your statements, particularly the two above.
(1) You could not know how much I wished I found lightning protection to be as simple as you describe. I nor anyone I know or have known in the radio and television broadcasting industry have ever been able find this task simple.
(2) For me lightning is utterly capricious.

I am fortunate to have a role where I learn something new every day and lightning protection at broadcast facilities is so dear to my heart that if you are on to something that takes all the complexity and variability out of lightning protection I am genuinely eager to learn.

James