Spline Balls on Transmission Lines 8

[bahrra]

I have a 69 kV circuit thats elevated in respect to the surronding area. The area in general is a high density lightning strike area. So the circuit being the highest structure by far has made it quite the targer for lightning. The underbuild 13 kV distribution has one of the lowest reliability ratings on our system due to trips and equipment failures(underbuild distribution is very susceptible to strikes). My company currently installs spline balls in substations but I want to install them on each pole. I am hoping this will prevent some stikes. This in turn should reduce some outages in the short term and help with equipment failures in the long term. This has caused quite a stir. Some people say they wont work, some say it will, some say it will attract lightning and make it worse. As installing a spline ball on each pole (spans lengths approximately 200 feet) is relatively cheap, I want to give it a go. I have contacted the manufacturer but I wanted some third party info.

 

[Skogsgurra]

bahrra,

Spline balls are considered superstition among serious guys. I have not seen any proof that they work. And no good theory that explains how they are supposed to work. I would not recommend using them.

 

[jghrist]

See the following for debunking air terminals that are supposed to prevent strikes:

Scientists Oppose Early Streamer Air Terminals

http://www.lightningsafety.com/nlsi_lhm/charge_transfer_opp.html

Charge Transfer System is Wishful Thinking, Not Science

http://www.lightningsafety.com/nlsi_lhm/charge_transfer.html

The Applicability Of Lightning Elimination Devices To Substations And Power Lines

http://www.lightningsafety.com/nlsi_lhm/MousaIEEE.doc

The Result of a Court Case Concerning ESE Devices

http://www.lightningsafety.com/nlsi_lhm/ESE_court_case.pdf

There Is No Magic To Lightning Protection: Charge Transfer Systems Do Not Prevent Lightning Strikes

http://www.lightningsafety.com/nlsi_lhm/magic.pdf

A Critical Review of Nonconventional Approaches to Lightning Protection

http://www.lightningsafety.com/nlsi_lhm/Uman_Rakov.pdf

 

[subtech]

Let me start by saying that I'm not a P.E., however, I've spent years in substation construction, maintenance, and operation so the subject of lightning is one that concerns me almost daily. Although I'm sure there are many devices and practices that people will recommend throughout the world, there is only one "fix" that I truly believe is a big help and is as close to a "true" remedy for dispersion of energy from a lightning strike as you can get. That remedy would be properly sized and carefully installed grounding. Whether your transmission structures are steel or wood, a properly sized static or sheild wire that is connected to earth at every structure with a large enough copper conductor is the answer. Of course, once that copper conductor gets to earth level, there is work to do there as well. If you know you are in a lightning prone area, provide adequate earth contact by properly installing ground rod(s) (more than one in your case would probably be a very good idea) and making sure they are connected with connections that are specifically rated for direct earth bury service. To me, mechanical connectors are not to be used in this instance. It amazes me yet today that there are companies with lightning prone lines(and substations for that matter) who haven't yet discovered exothermic welds for making grounding connections! At my current place of employ, grounding practice has changed recently. Transmission line and substation structures are now solidly grounded using large(1/0 to 4/0) copper conductors. Ground rods are installed liberally and spaced several feet apart and are connected using exothermic welds. The results speak for themselves. Few if any flashovers to 13KV underbuild conductors have occured and the breaker operations during storms (in my estimation) have been cut by at least 75%. On wood pole structures, #4 solid copper wire is the MINIMUM conductor size(many times #2 awg and 1/0 is used) and in addition to a butt rap at the bottom of the pole, at least 1 ground rod (5/8 in. X 10ft.) is installed 4 to 6 ft. away from the installed pole butt into undisturbed earth. When grounding steel towers or any steel fixture that is subject to lighning strikes, carry the grounding conductor all the way to the top of that structure and attach directly to your shield wire. Don't allow "coils" or "pigtails" to be installed in the slack area near the shield conductor in these conductors either. Keep them as straight as possible and keep bends in the grounding conductor gentle and sweeping. Sharp or abrupt bends or kinks should not be tolerated. This "new practice" may ruffle the feathers of some linemen, but when they witness the results, the complaining should stop. Don't rely on the steel structure itself to carry the energy of a strike. Bonding the base of the steel using a 5/8in. X8ft. ground rod and a short piece of #6 copper is NOT proper grounding.(At least here in the middle of the U.S.) Now, grounding is not cheap by any person's estimate, but it sounds like you've had enough damage and destruction to warrant some expenditure on problem prevention. It has been my experience that grounding is without a doubt the most misunderstood subject at many utilities today. It seems the folks who make the decisions are always looking to cut expenses somewhere,(aren't we all?)but cutting the grounding is probably the LAST place where cost cutting should take place. I'd forget the splined balls and get some large copper conductor and some 3/4in. X 10ft. ground rods.

 

[Skogsgurra]

There's some "solid" advice! Star for you, subtech.

 

[itsmoked]

For shore! Star here too.

 

[bigbillnky]

Great advice subtech. Hats off and a star!

Bigbillnky,C.E.F.....(Chief Electrical Flunky)

 

[alehman]

From today's issue of EC&M Magazine e-newsletter "Electrical Zone":

Around the Circuit
IEEE Drops Lightning Rod Project
At a hearing in late March, the Standards Association of IEEE voted to terminate work on a standard to govern "Charge Transfer Systems" (CTS) lightning protection. Also called "Dissipation Array Systems" (DAS), a CTS uses exotic multi-point lightning rods that prevent lightning from striking a particular location. Started in December 2000, the IEEE project remained inactive during most of its initial four-year run. IEEE ultimately terminated it due to a lack of vendor-sponsored tests, which were supposed to establish the validity of the CTS theory -- the tests were never circulated to IEEE working group members for their review. Earlier this year, the National Fire Protection Association similarly turned down Lightning Eliminators and Consultant's request to develop a standard for CTS/DAS products. In a decision dated January 14, 2005, the NFPA Standards Council concluded that the manufacturer's request failed to demonstrate "ample basis in the scientific and technical literature to support meaningful standards development for CTS/DAS lightning protection systems." The decision marks the first occasion since 1989 that the NFPA has denied such a request concerning the concept.

 

[Skogsgurra]

Thanks ahleman. Much needed.

I think that your post and subtech's put an end to this theme. Most enlightning!

 

[mc5w]

One of the members of this forum works for a Colorado electric utility and says that on the portions of their systems that have 17 foot ground rods they have ZERO lightning damage. This is done using ground rod couplings. You can get both threaded couplings for use with factory threaded rods and threadless couplings for use with ordinary ground rods.

When putting together threaded couplings please use Burndy Penetrox(R) E or Thomas and Betts Kopr-Shield on the threads. When putting together threadless coupoings please clean the copper surfaces with #220 silicon carbide abrasive paper and apply Ilsco Deox(R).

Probably how the lightning prevention idea got started is that the electrostatic precipitators for coal fired plants when polarized 1 way seemed to repel lightning and when polarized the other way attracted lightning.

In a Smog Hogg air cleaner for industrial machine ventilation half the plate cells are in the wire poistive mode and the other half in the wire negative mode. This produces a neutral charge exhaust stream that is less likely to paint the walls with microparticles that the plate cells did not get.

 

[Barryng]

About 25 years ago I looked at two systems for protecting a combined cycle power plant from lighning induced transients. This plant was a first generation plant. Although it was very highly automated and computer controlled (1975 vintage), there was virtually no transient protection on any of the hundreds of sensors feeding into the control building. This plant was in an area with a very high isokeraunic level so plant reliability was much less than desireable. The actual lightning strikes were not an issue because all the structures (boilers, cooling towers, etc.) were very well grounded. The problem was lightning induced transients in the various (mostly in underground conduits) instrument cables.

One system I looked at consisted of convential transient protection using properly grounded supression devices (e.g. MOVs) where each sensor cable was terminated in the control building. I had a very high degree of confidence that this system would function as designed but it had the disadvantage of being very expensive.

I also looked at a system proposed by a consultant that claimed he would ELIMINATE lightning strikes in the protected zone. He used "barb wire arrays" that essentially consisted of many thousands of air terminals. Since each air termninal saturates at some maximum current the idea was to parallel thousands of current paths to establish a relatively high total current. The consultant claimed he could "run down" the charge in the ground under the arrays, thereby eliminating any electrostatic attraction to lightning in the protected zone. This system had the big advantage of being simple to install and relatively very inexpensive.

I conducted quite a bit of research on the lightning elimination system. I spoke to a number of past customers that had used this consultant's products. The reports covered the entire spectrum. For example, one FM station in Florida with an exceptionally high tower claimed he was "sent from heaven" and solved an old problem but another large well recognized corporate client used the term "snake oil" and had removed the arrays. The conventional lighning "experts" were universally aligned against this system and took much pleasure in showing a photograph of lighning striking one of the consultant's barbed wire arrays. At the time, the conventional lightning consultants did not carry much wieght with me because the lightning elimination consultant presented a significant threat to them (by their own admission).

I came to the conclusion that this consultant did indeed have a system that "strongly tended" to prevent lighning from striking a protected area but it did not 100% eliminate strikes. My application required 100% reliability because I needed to prevent lightning induced plant trips. We bit the bullet and used a conventional approach. However, it is not uncommon, at least in Florida, to see barbed wire umbrellas mounted atop high mast lighting and other towers. It appears to me that this type of system has its application if the goal is only to significantly reduce the incidence of lightning strikes in a given location.

I would suggest that the Dissapation Array Systems not be discounted because I do believe they have value if used in an appropriate application.

 

[BL1]

SUBTECH---WE'RE TALKING OLD SCHOOL AND GETTING THE JOB DONE.SUPERB.WORDS TO ENGINEER BY.A STAR--THANKS.