Overhead Power Lines, Earth Conductor Injured Because of Lightning

Move it. Sorry to say that if the line is in an area with high keuranic levels and you have done all the proper protection methods then you either reroute the line or put it underground, both of which are probably orders of magnitude more expensive than fixing the shield wire(s) or improving the tower grounding system(s).

How could we retrofit existing earth conductor and tower grounding system ? Maybe put to thirth earth conductor ? There is nothing to retrofit for each of tower grounding system. It is not a suitable solution because of its high cost. I want to learn that whether conductor injury is directly involved value of pylon grounding system.

This is not a problem that can be solved by total strangers who have no knowledge of the source, installation, age, maintenance, environment or capabilities of the personnel now involved with the line. No clues from you, not even a picture.

From the sound of things, you don't have anybody on staff who understands the above or who has the ability to help you.

I assume that your goal is to save money by not having to do any maintenance on the system.

By hiring a LOCAL consultant (yes, it means spending money) you may be able to reduce the maintenance costs enough to justify spending the money on the expert.

You NEED an expert, not unknown strangers with no reason to help you.

I am going to put some picture tomorrow.

This is just a guess, but is it possible that at the point of lightening strike there is enough heat from the arc to melt the outer strands, but that the whole cable is able to carry the current without failing. If the cable is under tension (which it would be), the failed strands would separate as is shown in the pictures.

The line showing the damage is ridiculously over-tensioned.

What is the voltage of the transmission line. What size conductor are you using?

When you use the word "injury", what do you mean? Is the area known for a high incidence of lightning?

420 kV, Phase conductors: 3 bundle 954 MCM, Earth conductors: 96 mm^2 EHSS steel and 96 mm^2 OPGW The line route is highest incidence of lightning of our country.

What size earth conductor are you using?

When you use the word "injury", what do you mean? Is the lightning stroke

damaging the earth conductor?

I could say I know the exact solution for your problem. I could then give you a very good technical answer that looked like it was from MIT or Cal Tech. You would love that answer and give me a GA but not need to pay me anything. You would make the changes with a lot of money and find out it doesn't work but makes the condition worse. You would go back to CR4 and try to find me and threaten me with a big lawsuit. I'm too busy making up more false answers to others who are trying to get a great answer from a bunch of freebees on CR4. I have a huge smile since I have found one more fool to believe a devious answer.

Spare yourself from this situation. Find and hire a good, and probably expensive local professional to handle the problem solving. They will probably charge more than you think you should but you get what you pay for!

P. T. Barnum- "You can fool some of the people all of the time; you can fool all of the people some of the time, but you can never fool all of the people all of the time." Don't be a fool!

Good Luck, Old Salt

GA

A very good "point"!!!

Speak to the Consultants who designed it.

A lightning strike creates high temperatures that may cause the high tensioned cables to snap. Perhaps a Kevlar or Glass core cable may work.

Wait tomorrow for new photos. You all are going to see that unique reason is absolutely ligthtning strike. It is apparent like day...

I look forward to this event. And I am happy to be proved wrong. I simply cannot see the lightning damage as there would be far more catastrophic burning, carbonising and far more damage to the entire conductor. Fused ali to the underlaying strands, spattering of conductor.

I just don't see it and the way the strands have broken indicates previous damage to the strands.

I would strongly recommend a corona camera survey of the conductors length. I fear you may find more than you realise and that lightning is simply amplifying the existing faults on the conductor. I had a similar effect in Australia and it was bad installation of the conductor from bad handling, scuffing of the conductor on fences and being dragged on the ground. A year later the line dropped out the air and caused a bush fire.

Also, this damage seems to be limited to the outer stranding, in your photos. Is the damage to the inner stranding along the line?

Keen to see the photos you have. Is this OPGW, AAAC or ACSR conductor? What is your strike per year to ground count? What is the resistivity measurement you have to ground at the pylons? Is this damage limited to certain spans of the line or does it affect the whole line length?

I saw there is some sort of fruit farming below the lines, I would assume the earthing to be quite good in this area, but to say lightning is doing this damage on a regular basis, I just cant see it happening as it should jump to the line if the strike voltage and amperage is that high. There would be some flash over and far higher burning of the earth conductor.

You have my attention on this one.

Do you have any photo concerning break strands because of bad installation and corona ? I wonder form of broken? How does it happen ? I will evaluate this presumtion too on our other lines. But here, causer is obvious. Lightening strike.

You wrote (if I understand you correctly):-

But here, causer is obvious. Lightening strike.

Many here disagree with that statement. They are saying that it does not appear to lightning, but some other reasons - handling damage for one. But several other possible reasons were also mentioned....

It appears to be missing (in the photos) the sort of damage that many here would expect from a lightning strike as being the main cause....even though lightning may be the "final" reason that the damage is made apparent..

I do believe that storm conditions stress these cable to the point that they break but from what I can see so far it isn't lightning damage. This is lightning damage.

I agree with you entirely.

Also with several other people here.....

Your picture is to me really excellent, blackened and melted, exactly what I personally would expect....

I am no expert with lightning, having a good friend who REALLY is! But he is on a long visit to southern Europe at this time....

I was surprised that the earthing values were so high (20 Ohms or more!!), is that typical in your experience?

In this pdf they speak of 0 Ohms.....

Ground Resistancemeasurements.pdf

Also here:-

earth_ground_testing_technique.pdf

Lets hope that language does not get in the way for all of us to help this Guy....

It depends greatly on the soil conditions but I was surprised enough of the twenty plus ground impedance. Since this grounding is for lightning protection of the grid and not power return connection or a low impedance ground for a building I am less critical due to ignorance on my part.

Let me add a little reverse analysis here. Your proffered "earth ground testing technique" literature uses an instrument that can measure up to 800K ohms. This is more than five orders of magnitude more than we are both feeling nervous about. Why would they build an instrument that could read that high then?

I'll chalk that uncertainty up to unfamiliarity. I do know what a lightning strike should look like.

We need to know the thickness of the conductor shown in your pictures.

Is that the whole cable or just one conductor? Unclear.....

You need to have a a real close "closeup" picture as CR4 does not transmit much detail, or give us a link to another website where we can download or examine high quality pictures......

From the Photos you have posted, it could even be a snake..... Sorry, but they are no help whatsoever...just a waste of time.

I could send it to ur e-mail

I am going to take some photos closer. Wait for me.

I agree that these images do not help us understand what caused these cables to break. I will say that I believe these images support my opinion that this is not due to lightning damage.

When lightning makes a direct strike the energy is so intense that fuglurites are frequently formed. These tubes of fused soil can be considered petrified lightning. The chaos and magnitude of energy is always evident when lightning repeatedly strikes. The cables are much too neat. Individual strands are snapped in the previous photographs. In these images the fusing I think I see at one of the ends looks more like a controlled cut from a torch on a cable not under tension.

Dare I say "OUR opinion"?

I will send scaled picture. I hope we will reach a good conclusion in the name of solution

Thanks for the photos. I feel it is pretty safe to conclude that the initial damage has happened from installation, and the strike has only furthered the damage and exposed it for you

I do feel I am safe to say that all the broken strands are on the outside layer of the conductor. You have no internal layer strands breaking.

Strip down a section of conductor, layer by layer, look for pitting of the strand surfaces over a distance of about 450mm from where the above layer strands have snapped. If you find pitting, test it for traces of nitric acid in a gas chromatograph or by another test method you have access to.

I strongly suggest that the conductor is replaced using good, clean, smooth surfaced running out blocks, a good condition drum with no nails left in the rims. Hang a clean soft cloth on the conductor as it is being pulled out. (Silk or similar fine texture material). The cloth should snag on any nicks or scuffs in the outer layer. You can do this at each running out block and anywhere the cloth snags, then you know where the cause of the damage is. Any scuffs need to be smoothed to reduce corona.

90% Sure this is not lightning damage, but sure the lightning is highlighting the existing damage and weakened conductor. (The conductor damage existed before the lightning strikes).

Also check the strands for metal fatigue and check the strands for elongation against the specification and allow for age. If the line is over tensioned the elongation result will show this up. (Instron tensile tester). Quick field test: two strands. Spiral one strand around the other to form a close coil. As if winding around a mandrel to make a spring. Check the 'coiled' strand for surface cracks and fractures and brittleness. This will provide an indication only, of the condition of the existing strands. A lot of surface cracks shows fatigue.

Let us know what you discover.

I particularly liked the sentence of yours:-

90% Sure this is not lightning damage, but sure the lightning is highlighting the existing damage and weakened conductor. (The conductor damage existed before the lightning strikes).

I feel that it is right on the money, someone else did too if I remember correctly.....

I should have asked this previously. Is your SCADA system going down on each strike? How often are you changing out fibers on this conductor? This is a give away if this is lightning, as you will have lost fibres from each strike. Check all the fibres for continuity and Db losses from end to end. Where you have damaged fibers, (losts continuity), you can locate the spans which have sustained the most strike damage.

There is no problem at fiber communication. Fibers are sound. We check the line every three months. We dont change fibers or condustor. We fix it as you could see pictures. Just fixing with shield strands.

(Orage days) Electrical storm day:40 days per year in this area. And It is OPGW, 96 mm^2. Corona occur on phase conductor not on earthing conductor. We have no problem on phase conductors. Each of Tower earthing resistance must be less than 20 ohms. But some of that higher than 20 ohms where ground is rocky. This damage doesnt change depend on span. That is to say it occurs whole line length.

If I was you I'd still consider mechanical damage to the line.

Can you demonstrate that it is not mechanical damage ? Would be interesting to see the other pictures.

What is the ground resistance at your pylons? Ideally it will be 15 ohms or less.

Now if we could only find a way to limit lightning outside of the lab to only 200 coulombs of charge.

<end snark mode>

Nice find.

This charge is outside the lab.

Great paper and it appears to support our thoughts further....

Looking at these low resolution images, it looks like some of these breaks are from cable stretching. Specifically the upper right end in the top picture. Some of these breaks look like they've been cut. Notably the lower right wire in the top picture. The lack of tool marks implies to me a shock wave type of break from either under damped standing wave motion or a sudden sharp mechanical impulse.

The OP has sent me an email with several pictures of better quality than before (though the pictures he posted today here are not in them. They appear to be more in line with strike damage).

If anyone would like a copy of those pictures, he needs to send me a private CR4 email with a "normal" email address contained in it....CR4 email does not allow pictures.

DO NOT POST NORMAL EMAIL ADDRESSES HERE IN CR4!!!!

I personally am of the opinion (with help from the experts here), that some form of mechanical damage when installing or bad production/storing methods are primarily to blame.

The final problem then being caused by the lightning strikes on the already weakened cable (assuming that the cable is of the correct type, though to my untrained eye,the steel appears to be on the outside....!), though I feel that they are not the primary reason for the failures. I could be wrong.

So what needs to be controlled are the following:-

1.Production methods & storing of cable (a too small diameter storage drum could be a real problem for example).

2.Cable type (steel wires inside or outside), thickness and tension when in use. (Installing in summer with the tension for winter temperatures for example). Possible lowering of the overall tension (lowering cable nearer to ground or better, also higher pylons for example)

3.Cable size with regard to the size and frequency of lightning strikes, especially in problem areas.

4.Manner of installing and care of the cable. Too much rough handling. Incorrect tools, too small a work gang.

5.Maintenance/lubrication etc..

6.Pylon earthing appears to be too resistive possibly needing better earthing

I am sure that my list is far from complete (or correct), so please jump in an add to the list please....or correct my thoughts.....

"It's the last straw that breaks the Camel's Back!" so to say.....

See here:-

Straw_that_broke_the_camel's_back

engilis, what do you make of this detail:

Just a few strands are damaged, but the strands immediately adjacent to the damaged strands show no signs of harm. How do you explain this on the basis of lightning alone?

Okey I give you right but How did it happen that appears burnt, fused and soot on point of strands? Like Ramconsult said that My first work is that reevaluate the sag/tension calculations and measuring in case whether it is right actual sag/tension according to sag/tension list. I will check. MANY THANKS TO ALL COLLEAGUES

How did it happen that appears burnt, fused and soot on point of strands?

From a little guess work it seems that the strands were broken already and the sooting, burning occured with a lighting strike arcing over the strands.

Everything still points to mechanical damage.

Good luck!

The break makes them "more attractive" for possible lightning hits, if I understand you fully. Which would fit in well with the way lightning conductors are made for example....

Then lightning routinely strikes the Towers, sometimes it strikes earthing conductors (According to comments I guess, 2 times happened (1,2,3 pictures are same event, and other last picture) Wrong choose and installation of OPGW conductor, excessive strained, small diameter, thin strands.

Aluminum nitride (tan/grey) in combination with a slight amount of carbon impurites would be my guess. A chemical assay would tell you.

What was the outcome of this line problem? Any feedback or updates on this? Curious to know the outcome.

On tower top fix a cross arm and string multiple,parallel ground wires in areas where you experience more damage.