What is the effect of running coil connections parallel to each other?

[Beaufort]

I've searched the board and haven't found anything to address this.  If you look at the coil connections on a 3-phase alternator, they seem to run parallel to the connections from other phases.  So the "coil 1 finish" to "coil 4 start" wire runs next to the connection between coils 3 and 6.  Won't there be a negative effect at higher amperages due to the opposing EMF between the phases?  It seems like these runs should be kept apart from each other or shielded, or is the EMF not strong enough to make a difference?  

I'm working on a switched Delta setup and trying to chase down any sources of electron resistance...maybe this issue is more important in Delta than Star due to the nature of Delta wiring?

[SparWeb]

Start with this:

...So that you now have a diagram to refer to.  When making changes to coil connections, make sure you are orienting the coils the right way, or, as you say, the EMF will cancel.  There is a numbering convention in 3-phase AC motors that you can follow, even if you've building a homebrew machine.

Speaking of the convention, I find it hard to directly answer your question.  Look at my diagram, and I have "wire 1" at the start of the coil that ends in "wire 4".  That coil is in phase A, and its mate is the coil between "7" and "10".  These two coils can be connected in series (1-Y or "series-Star" or "series-Wye") or in parallel (2-Y or "series-Star" or "series-Wye").

I'm going to post this and come back later when I've been able to dig up a link to a very useful document on the Baldor website that explains a lot of this.

[SparWeb]

Hmmm... since drawing up that diagram I have since learned that "Generator" refers to a machine with a commutated DC output, and an "Alternator" is a machine with an AC alternating current output.  Forgive my terminology gaffe - we are talking only of "alternators" here.  I could re-draw it, but I think everyone gets the point.

[SparWeb]

Baldor Cowern Papers www.baldor.com/pdf/manuals/PR2525.pdf

The whole thing is very valuable.  Look on page 58 for Wye and Delta Diagrams.

[Beaufort]

Steven, thanks for the info.  That diagram you made has been hanging in my shop and a great visual.  

I understand the coil wiring scheme for Delta and Star, but my question relates to the actual wire routing between the coils.  A convenient way to wire up a stator is to run all the connecting wires through the same channel and tie them together.  My question relates to the inductive properties of a wire carrying current next to another wire, and if the coil-connecting wires should be kept apart from each other?

[Flux]

The effect is minuscule just don't worry about it. Even when these connections are within the rotating field you are only looking at the effect of one turn in the total number of turns per phase.

Outside the rotating field the effect is virtually unmeasurable.

Flux

[ChrisOlson]

If you redraw your diagram at some point, you could consider changing where it says "Star-Point" to "Neutral".  The star connection in a wye-configured generator is the neutral and it's common to see 4-wire 3 phase with the neutral coming from the generator or transformer with wye configurations.  The neutral is usually used for fault protection but you can run single phase loads with a wye-configured system between any leg and neutral - the phase to phase voltage is 1.73x phase to neutral.

Delta-configured generators/transformers do not have a neutral point.

Power transmission is typically done with delta systems and the transformer at the load point has a delta primary and wye secondary to provide a neutral, which is grounded at the service entrance.

If you wish to run single phase AC loads with your wind turbine at some point with a star-wired generator, run the neutral into your AC service and ground it to provide fault protection, and you can do so.

--

Chris

[scoraigwind]

Chris wrote:

"If you wish to run single phase AC loads with your wind turbine at some point with a star-wired generator, run the neutral into your AC service and ground it to provide fault protection, and you can do so."

It's funny, but although I habitually do (have) refer(ed) to the star point as "neutral", I have just started trying to train myself not to.  

Strictly speaking the neutral is the grounded wire in a supply.  However it would be a rash idea to connect the 3 phase output from a wind turbine permanent magnet alternator to the AC supply arriving from the mains.  Even connecting the neutral to ground/earth would not usually be a clever move.  

In most battery systems, the battery negative is grounded or the battery is floating.  If the star point of the alternator stator is grounded, then the battery terminals will wobble around approximately equidistant from ground (except in calms).  This would necessitate double pole fusing and probably result in various other complications.

Anyway I have personally never heard of grounding the star point on a battery charging alternator, and hence I am trying to stop calling it the neutral.  It's all about words and so it may not be important, but I do think the word neutral does convey a grounded status to most people's minds, even if only unconsciously.  And the unconscious is responsible for a lot of prejudices and misconceptions if it is misinformed.

Connecting coils in parallel and/or delta will usually result in some parasitic losses in low winds due to unbalanced phases, or third-harmonic currents in the loops of wire.  Running two (different) phase wires physically parallel in space is normal practice, but make sure they are well insulated from each other - not just by the enamel on a winding wire.

[Ungrounded Lightning Rod]

If you look at the coil connections on a 3-phase alternator, they seem to run parallel to the connections from other phases.  So the "coil 1 finish" to "coil 4 start" wire runs next to the connection between coils 3 and 6.  Won't there be a negative effect at higher amperages due to the opposing EMF between the phases?

The mutual inductance of two wires running parallel is minuscule at the frequencies we're dealing with unless the parallel run is measured in miles.  It only matters if the wires are running through a slot in a core (where the core magnifies the flux coupling between them by a large factor) or between the poles of a rotor (where they pick up a non-trivial amount of induced voltage from the enormous moving mag field of the rotor's magnets).

In fact you usually want the wires running pretty close together whenever they're not in a conduit.  That way, if there are lightning or lightning-surge currents nearby, they don't form a big pickup loop.  Lightning currents are VERY high frequency (due to their abrupt start and stop) so their (also:  very large magnetic field couples very strongly to a wire.  If the wires run parallel and close together they tend to pick up roughly equal voltages and the voltage between two of them at the load is not all that high, compared to running them far apart so they pick up different induced voltages which can produce an enormous voltage spike between them at the load.

[ChrisOlson]

Hugh wrote:

Strictly speaking the neutral is the grounded wire in a supply.  However it would be a rash idea to connect the 3 phase output from a wind turbine permanent magnet alternator to the AC supply arriving from the mains.  Even connecting the neutral to ground/earth would not usually be a clever move.

You may have misunderstood what I was saying.

Neutral and ground are two different things.  Neutral is commonly referred to as "ground" in a single-phase service, but this is not correct.  The neutral IS grounded because the transformer that converts the delta three-phase transmission power to service power uses a delta primary with a grounded wye secondary, specifically to provide that grounded neutral for service power, and fault protection.

Secondly, whether you run a three-phase wind turbine, a genset, or any other type of generator, to be compliant with electrical code (in the US anyway) you must provide either switchgear to disconnect grid power and hook your generator to your service, or provide a separate AC service for the generator.

My wind turbines feed their own three-phase AC panel.  The AC power from the turbine panel is fed thru a three-pole circuit breaker to the rectifier box where DC power is made.  The neutral from the generator is wired to the neutral bus in the panel, NOT the ground.  The ground is provided by a separate ground rod driven at the service entrance, and the neutral is grounded with a separate ground rod at the service entrance.  Even with a grounded neutral the neutral wire carries power in normal operation (running anything on single phase, for instance).  The ground never carries power unless there's a fault.

If you do it any other way (in the US) you're out of compliance with electrical code and I know of no inspector who will pass it.  And if your house insurance company finds out you did it any other way they'll probably cancel your policy.

Now, if you want single phase power from your turbine AC service you have the same thing you have in your house - a three wire outlet with power from one phase, a neutral, and a ground.  And the circuit from the turbine AC service to the outlet is protected with a circuit breaker or fuse.  You connect any AC appliance to one leg and neutral and it will operate if it has the proper voltage and frequency supplied to it.  You check between neutral and ground in the outlet and you have no power.  You check between the phase leg and ground and you have a fault, and you'll get some voltage - whatever voltage will travel thru the earth from the ground rod to the neutral rod.  You check between the phase leg and neutral and you'll get whatever single phase voltage the turbine is putting out.  Note that when you do this you do NOT have fault protection if you use an appliance with a polarized plug that does not use the separate round ground prong if you do not ground the neutral wire at the service entrance.

I use both diesel genset and wind turbine for power here, and there's no difference between how the two are wired to their services.

--

Chris

[Beaufort]

Thanks to everyone for the responses.  The consensus is parallel hookup wires are fine (properly insulated).  

[12AX7]

Hello!

I'd just like to comment to the terminology use here.

Hugh wrote:

Strictly speaking the neutral is the grounded wire in a supply.  However it would be a rash idea to connect the 3 phase output from a wind turbine permanent magnet alternator to the AC supply arriving from the mains.  Even connecting the neutral to ground/earth would not usually be a clever move.

Here in the US the word "strictly" would be incorrect.  Most all homes with grid power are supplied with signal phase (two wires with 240volts across them) and a ground.  Where the voltage between either of the two legs and the ground about 120v.

In the homes breaker/fuse box this ground wire is tied to the ground buss/lug.

All the outlet/light neutral (white) wires are tied to this same ground buss.

These white wires are called "neutral" and are not to be confused with "ground".

Each outlet and lamp fixture should have a "green or green with a yellow stripe" tied to the outlets (third prong)terminal,  which should be connected to the "neutral buss" located in the main panel.

All the lights/outlets (that are supplying power to a load) have current flowing on both the hot and neutral wires.  Even though power can/will flow from the hot to ground, this condition would be considered a "fault"

Thus,  the neutral and the ground wires have their own color code and terminology.

ChrisOlson wrote The ground is provided by a separate ground rod driven at the service entrance, and the neutral is grounded with a separate ground rod at the service entrance.

I don't have a license but this doesn't sound proper to me.  Two separate grounds suggests the chance of having a potential between the two grounds, which could create a dangerous situation.

If I screwed this up anywhere... someone please speak up!

ax7

Mark

[ChrisOlson]

Mark wrote:

I don't have a license but this doesn't sound proper to me.  Two separate grounds suggests the chance of having a potential between the two grounds, which could create a dangerous situation.

Mark, I just looked it up.

Code says two ground rods at least 5/8" in diameter, minimum 8' long, maximum 25 ohms, and the rods are to be placed at a distance from one another equal to the length of the rods.

Generator sets are required to have a neutral ground at the generator, and a separate generator frame ground at the generator, with the rods placed according to the code above.  At the service entrance two more ground rods are required placed according to the code above.

With delta generators only the frame ground is required at the genset, and one ground rod placed at the service entrance.

And that's exactly how my 250 kW Cummins genset and our service entrance is grounded - and it's a star genset because of the wire run.  It's 1/8 mile from our house.

--

Chris

[SparWeb]

You might want to look for a book called "Electric Motor Repair" by Robert Rosenberg.  You may be able to find it in used bookstores or internet used book sellers.  It's only for "repair" of the motor, so it doesn't get into the details of "why" it is the way it is.  Still, for picturing the process of rewinding AC motors, I've gained a lot of insight from it - even if I haven't re-wired one yet myself!!

[SparWeb]

"changing where it says "Star-Point" to "Neutral"

You can see this in the Cowern Papers that I posted, in fact.  Baldor is concerned with motors running on 3-phase utility service, however.  Not my spit-and-baling wire contraption in the back yard.

When reading about 3-phase circuits and systems (not very much I admit) I do find disclaimers that read like "In a balanced 3-phase circuit...".  This I think is the crucial factor to consider.  I strongly doubt that a PM alternator doing battery charging would qualify as "balanced 3-phase".  I'm rather tempted to fire up one of my simulator programs to see what it says about the Star-to-ground potential difference when the generator is unloaded and loaded.

[ghurd]

Beaufort,

correct me if I am wrong...

"working on a switched Delta setup", posted in 'wind', means unstable RPM, frequency, voltage, amps, and watts?  Meaning you want to charge a battery.

SparWeb,

Put this in your simulator and smoke it.  I mean see what smokes. LOL

The Star-Point is Neutral, which is grounded. And the battery negative is grounded.

POOF?

.

Anybody?

"Neutral and ground are two different things.  

The neutral IS grounded... specifically to provide that grounded neutral."

Uh... What?

"The neutral from the generator is wired to the neutral bus in the panel, NOT the ground.  The ground is provided by a separate ground rod driven at the service entrance, and the neutral is grounded with a separate ground rod at the service entrance."

Thank goodness that 'single ground' concept is all straightened out?

"If you do it any other way (in the US) you're out of compliance with electrical code and I know of no inspector who will pass it."

A wye configured machine with a neutral "Star-Point" not connected to a grounded neutral will not pass inspection for grid connection unless the neutral is grounded and connected to the star-point that is not connected to the grounded ground, but it must be connected to the grounded ungrounded grounded neutral?

.

Beaufort,

This is a dual rotor, or Zubbly, or other homebrew machine?

Sorry, but expect the 'details and tolerances' will be far enough off that Delta will be fighting / shorting / circulating within itself.

The output results will be better and/or more efficient if Delta is changed to Jerry Rigged (phases individually rectified, then paralleled after the diodes).

I never made a machine that made as much power in Delta as it did in Jerry.

YMMV

G-

[scoraigwind]

I really just wanted to point out that the star point on a three phase permanent magnet alternator should not be grounded, and hence should not be called a neutral wire.  

I stand by my statement that the neutral is the name for the wire that is connected to ground (worldwide including in the USA).  I am well aware that this does not make it a ground wire as such, but once it is connected to ground this has implications for the potential of other wires in the circuit.  In the case of a 3-phase pm alternator feeding a rectifier, grounding the star point will conflict with grounding the battery negative, which is a more common practice.

I hope this makes more sense.

[Beaufort]

Hi Ghurd, the only reason Delta (axial flux, dual rotor) was mentioned was because of the thought that the induced currents between wires would have more of an effect with that configuration.  I was testing a non-standard magnet-coil setup and got results that didn't match theoretical at higher amps, so I was eliminating some of the possible sources.  I've since changed my magnet-coil shape, configuration, and wiring harness to something that matches theoretical, and now can play around with the different wiring configs (like Jerry).  

[ChrisOlson]

I'm very concerned with proper grounding being we're off-grid.  So after participating in this discussion here I talked to a licensed electrician with a Master's this morning.  After finding out, while talking to him on the phone, there's more to it than meets the eye I had him come to our farm and properly ground our system.  It cost me $250 but it was probably worth it.

I had my wind turbines grounded wrong and I did not look closely enough at our genset grounding to see how it's done.

The electrician told me that if you run the neutral from the generator to your panel the neutral must be bonded to the ground in the panel.  Then a separate ground wire (sized to the panel capacity) must be run from the panel ground to a driven ground rod.  If you use only one ground rod the grounding system must be "ohm'd out".  If you use two ground rods it doesn't have to be "ohm'd out" but the wire must be continuous, i.e. you slide the "acorn" up the ground wire to the first ground rod and tighten it, then run the wire to the second ground rod and terminate it.

It's important to note that you can elect to not run the neutral to the panel (a.k.a. ungrounded delta).  But if you run a six-wire generator cord to make a star/delta switch in your panel, then you have effectively run the neutral to your panel in wye and it must be bonded to the ground to make it legal.

He told me that it doesn't matter what kind of generator it is, even if you have a gerbil spinning a wheel in a cage and it makes electricity that you wire into a building, the electrical code applies.

I didn't notice the continuous wire between the ground rods before.  He said I had too many ground points, which is just as bad as having none because I was creating a potential between ground points.

He also told me that if you use a switchgear that the utility neutral must be disconnected from the panel neutral when you go from grid to standby power.  Then your generator neutral is grounded thru the service panel ground rod when the switchover connection is made by the switchgear.

Just thought I'd pass along what I learned this morning.  I had it mostly right, except for grounding my generator neutral before I brought it into the building, then grounding it again in the panel, and I used separate ground rods to do it.

--

Chris

[Beaufort]

Wow Chris, great info!  Did he inspect it to NEC or to UL standards?  How is your tower  grounded, and did that pass?  Also, I've always wondered about grounding the steelwork of the alternator to the tower and then true ground.  The pipe-over-pipe yaw bearing wouldn't pass muster for a proper ground, so another wire in the drop cord would be required.

So for a Star/Delta/Jerry switch, it sounds like doing it up on the machine would save some hassle at the panel in terms of grounding?

[Ungrounded Lightning Rod]

Of course if you bond a "neutral" to ground in your panel you have to UNground your DC side or install isolation transformers.

I think there may be a confusion here in the application of the code.  Or else the code didn't take into account a delta-Y switched windcharger.

[12AX7]

Mark wrote:

I don't have a license but this doesn't sound proper to me.  Two separate grounds suggests the chance of having a potential between the two grounds, which could create a dangerous situation.

and Chris wrote:

I didn't notice the continuous wire between the ground rods before.  He said I had too many ground points, which is just as bad as having none because I was creating a potential between ground points.

That's what I thought!

ax7

Mark

[ChrisOlson]

Firstly, for Beaufort;  Matt, the electrician, told me that I should consider installing a lightening suppression system on the tower.  He didn't say what that consists of.  He's got a Master's electrician license so I can only assume that the work he did for us today is up to code standards.  He looked over the rest of my stuff and he didn't seem to think there was a problem with it.

In reply to Ungrounded Lightening Rod; The electrician removed my battery ground rod and told me that can't be grounded.  He told me to quit creating more ground points.  Actually, his exact words were, "Did you get a good deal on ground rods someplace, Chris, and just decide to buy a truckload of 'em?"  The inverters feed their own panels, which are grounded thru the service, and everything that runs off those panels is grounded thru the service.  I guess grounding the battery does absolutely nothing except kill half wave on the rectifiers.  He said the only reason it worked is because I had the battery ground rod far enough away from the service ground (about 75 yards) so there was no potential between them.

In reply to Mark; Yep.  Your comment made me look at an old code book I got, and reading that created more questions.  That's why I decided to call an electrician this morning.  I wasn't sure I had it right, and being we're off-grid, if I burn something up because it wasn't grounded properly I'm pretty much screwed.  We got a 250 kW Cummins genset that provides the bulk of our power.  And if something happens to that genset I can have a rental unit here from Cummins N-Power within a few hours and we're back in operation.  But if I burn a building down and there was something not wired properly, our insurance probably won't cover it if they found out the wiring was not done by a licensed electrician.

--

Chris

[12AX7]

Hello!

I don't know what this "lightening suppression system" means.

Talking about lighting protection is a lot like talking politics,  you can spend the entire day yacking about it, but you don't know whats really right until after the fact.

I don't know how one could suppress lighting.  You can work towards avoiding it, or reducing it's effect when it hits.

My opinion is that dealing with lighting is exactly like Catch 22.

Everyone says (me too) that the answer is grounding, and lots of it.

The problem is, the more you ground the more you're reaching out to the Big Guy upstairs with a sign saying "Strike Here".

Lighting seeks ground, and the "higher the quality" the better.

I have never worked on or around a tower with a wind turbine on it, but I have worked with a number of antenna towers.  

Lighting protection is all about protecting the "equipment" in the "shack" and not so much the tower it's self.

We all know that a bolt of lighting is a HUGE amount of power, and for a very short period of time.  The only way (to my knowledge) to deal with this energy is to disperse it into the ground.

I installed and serviced lots (hundreds) of TV antennas mounted on roof tops.  In the years I did that on two occasions I saw the results of a direct strike on the antennas.  Both cases the ground cable that connected the antenna tripod to a driven ground rod had been vaporized.  The 300 ohm twin lead was a melted mess and the TV's were "toast".  The 16 - 12 gauge ground wire opened like a 1/2 amp fuse.

If your tower gets hit by lighting, and it wasn't grounded (per code) your insurance company will tell you... "too bad, so sad".

but at the same time,  grounding it is just inviting a strike.  catch 22

Chris wrote..  Actually, his exact words were, "Did you get a good deal on ground rods someplace, Chris, and just decide to buy a truckload of 'em?"

These would be a good beginning to grounding your tower.. if you can pull some of them out of the ground and drive them near your tower and use some VERY heavy copper wire from (4 or 0?) to tie your tower to the ground rods.  It would help if these ground rods made contact with the water table.

It's kinda funny, but in many rural homes that get struck by lighting, most will suffer burnt out submerged well pumps, and not their TVs and radios.  Lighting loves a good ground!

ax7

Mark

Lighting protection,  Damned if you do, damned if you don't.

[SparWeb]

It seems we all get to the point, with a hobby like this, where we confront our ignorance and start asking questions even though we know they are not easy to answer.  I've done my own investigation, come up with answers that make sense to me, and acted on the things that seemed to to be the most important.  The topic of lightning seems to come up, whether it's invited or not, on a regular basis.  It's too complicated to really resolve in a short quip so only those who've done their homework get the benefit from the discussion.

I'm signing up for a professional course in grounding and bonding electrical gear because I just had to admit I'm going to undersand this much better by "school" learning.

By the way, I did run a little simulation, like I said, just to get a measure of what the potential is between a star-point and the ground in a battery charge system.

This is for a 28V battery charge system.  The alternator has an open-circuit voltage of 40VAC, but current flows so voltage is clamped to 28V by the battery.  The voltage measurement "test pont" is the little hexagon at the bottom left.  So this is like touching your multimeter to the star-point of the alternator and the battery negative at the same time.  I think a verbal discussion about the flow of current from one AC phase to the next would also have been able to convey the fact that the star point is never the point of lowest voltage in a 3-phase battery charging system.  There is always a positive voltage above the ground reference in the alternator, therefore this CANNOT be connected to ground.

A ground conductor should not carry a current during normal operations, otherwise it violates the principle of being a ground conductor.

Personally:

1 Provide common casing ground between the inverter, AC breaker panel, outlets, etc.

2 Ground these with a single wire to a copper ground rod beside the RE system.

2 Connect a lightning arrestor across the + and - of the charge controller.

3 Ground the tower structure to an second copper ground rod.

4 Connect the two ground rods with a heavy copper wire (buried between them).

It goes without saying that this won't protect against all conditions, and there are many more measures to be taken to reduce the risk of many more problems.

This is quite far from the original topic, but I'm always concerned when conflicting advice is given about safety issues.  As I said, I've conceded my own ignorance on this very important issue and I think I need formal education on the topic to proceed safely if I intend to build higher towers or hook the RE to my house.

[scoraigwind]

I would always connect ground rods to each other since otherwise it seems to me that you are inviting them to become real hazards in the event they don't ground properly and end up being at a hazardous voltage relative to each other.  The ground has zero resistance they say, but the rod has a high resistance to ground in my experience.

However the 'best practice' here in the UK is to not connect the wind turbine tower ground directly to the building ground (actually we call it 'earth' here because we still speak proper English, but I will translate).  This puzzled me so I dug around a bit and discovered the reason.  Most small wind turbines installed recently in the UK are grid tied.  The grid has in many cases got a common ground and neutral conductor leading to the dwelling (saving a lot on copper - it seems that most countries do this now).  Sometimes this conductor has issues with its continuity, creating a dangerous potential on the grounding system at the building which is left connected securely to the 'hot' wire without a good connection to neutral/ground whatever you wish to call it.  For this reason there are strict regulations about equipotential bonding within the building to ensure that everything goes up to the same potential.  Now, coming back to the windmill tower...  its not a great idea to connect this to a grounding system that is likely to become a hazard in itself.

Nothing is simple :-)

[willib]

Hmmm

While investigating the "theoretical charge capacity" of silicon nanowires.

This thread poped up on google..

Funny how that worked. :-)

http://www.technewsworld.com/story/61254.html

Have a good day all

[fluxable]

I've got a house wiring book written by a professional, and he really stresses putting in a good ground with 8 ground rods (spaced 8 to 20 feet apart) for a house electrical system. But, it really depends on the resistance through the rods into the soil itself. There are many factors, such as moisture content of the soil and number of rocks etc... He states that unless you can prove 25 ohms or less in one rod, then 2 rods are inadequate for delicate electronic equipment.

So I think the best thing to do is look at your individual grounding system, and if for any reason think it's inadequate, to reinforce it with additional grounding rods for better protection. Of course ground wire linking them would have to be one continuous length. Once you have a good grounding system, you can put in surge suppression protector in for the ultimate in protection (providing you don't suffer a direct strike from lightning).

As for the tower, as Hugh mentions, it would be a good idea to ground it separately and keep that ground well away from your house ground, just in case it attracts the "lightning gods".

[JYL]

This is what I learn working for a Paging company with several 100 Meter antenna tower.

Tower/antenna should be earthed/grounded separately from other utility.  For large tower, multiple interconnect ground point with multiple contact point at the tower (rust can create problem over time) are generally recommended.  Some towers were equip with guy-wire that can conduct electricity efficiently... and all guy-wire were interconnected -- with the tower -- by special jumper cable.

Don't use any utility grounding equipment for that purpose:  (Phone, Electric or others).  This might damage their equipment in case you get a strike.

If your planed tower is close to a utility earth/ground (Phone, Electric or others), call them.  Now, the problem with CLOSE -- is that it depend on the conductivity of the ground (when it rain for a long time).  My radio engineer were pretty good to know when it has the potential to create a problem.

Electric utility did have pretty good track record with us.  They knew how to ground their stuff pretty well and not to interfere with us.  The TELCO have been another story all together.  Often, an antenna did get hit, the antenna ground protection diffuse the lightning strike to the ground... but the TELCO ground rod pick it up.    If we did have only a few pair of telephone wire at a site, that was not so bad... but for a the sites were we have a few 200 pairs copper cables... the damage have been extensive (3$Million, 5 $Million and 4.5$Million in repair for 3 distinct incident).  The damage have been pervasive at the site as well as at the TELCO site often located several miles from our CELL.    Believe me, replacing 400 Carbon at a single site -- knowing that the telco is doing the same at his end --- sound already alarming.  When 90% of the electronic is fried... that even more impressive.   

This kind of problem does not exist anymore... TELCO are forced to install fiber optic to reach those locations.

[Sr WiNdTeCh]

Bond, Bonded, Bonding   
Ground, Grounded, Grounding   

All with completely different meanings....

When will the NEC ever make it easy on us....

http://www.mikeholt.com/ 

Excellent website, excellent books, instead of buying an NEC book, buy his books, it 'dumbs' things down a bit.