IEC Specifications

I am pretty sure that standards can be obtained from the organisation they are from or from a web based vendor. I am afraid that this will cost money and I am more afraid that people might be reluctant to share this information for free.

You on the other hand seem not to be afraid to post your e-mail. Besides this being not allowed by CR4 rules I would say you should be afraid of all the spam that the spambots are going to send you.

Sorry no information about the test facility.

Why Oh Why do people insist on including their mail address in posts.

I've done the OP a favour by alerting the moderators.

I'm the senior moderator on a UK site, it gets to be a chore helping people after they have been warned in the site rules. Site rule that everyone just clicks "I have read." (No one ever does.)

Try http://webstore.iec.ch/webstore/webstore.nsf/artnum/045826!opendocument

Preview http://webstore.iec.ch/preview/info_iec62561-7%7Bed1.0%7Db.pdf

Only 70 swiss francs, print or download, in 2 languages (french/english).

32 pages total.

1. Professionals should obtain their own, legal, documents for use in their work.
2. Sharing copyrighted material is not normally acceptable practice, at least not in most professional communities.
3. Electrical Testing Labs in Delhi - Delhi Test House
4. Electrical Testing Laboratory - Shriram Institute for Industrial Research
5. Bureau of Indian Standards - Laboratory overview

lyn;

Nice to see you on this forum as well.

I found this tender copy and perhaps I do not understand what that specification related to capacitance is ? It says in the material specifications table capacitance >=1000pF/m (1nF/m). Is this between the conductor and remote ground? Where does this capacitance exist?

http://mrpu.etenders.dae.gov.in/tnduploads/mrpu/tnditem/TND00596001000000000000DAE02801.pdf

Advanced lightning protection systems utilise a coaxial downconductor.

That capacitance is that between the inner and outer conductors.

That list of downconductor specs that caught your eye look like they were cut and pasted directly from one of the manufacturer's spec sheets.

Wal,

Interesting one. How do you wire it as it is supposed to be wired to earth electrode dug out in the pit? How do you wire co-axial cable?

Are these for protecting signal lines or power lines?

Are these for protecting signal lines or power lines?

Neither. The downconductor goes from an advanced air termination straight down to ground.

The advanced air termination is a capacitive arrangement and the inner and outer conductors are joined at the bottom where they connect to the interred earthing arrangement on site.

Read all about it.

Wal;

Both inner core and shield are shorted at the lower end. I need to understand why it is done in this way. I will go through this document and will also look for more details before I can say anything. I have not done such thing so I have no idea of this technology.

Thanks for sending me this link.

Principal reason, according to those who manufacturer and sell these systems, is to eliminate or greatly reduce the incidence of side flash from the down conductor when its channeling energy to deck.

The capacitive arrangement at the top is there to encourage development of discharge streamers before direct strike conditions build up...apparently.

The Oz standards for grounding and lightning protection considers these advanced systems as supplementary to and NOT a replacement for direct strike protection. In other words put them in if you want to possibly eliminate a strike but don't rely on them totally ie put the regular arrangement in place for when a direct strike does occur in spite of attempts at lightning proofing.

A lightning protection system's principal purpose is to provide a preferential path for the energy and to eliminate or greatly reduce step voltages during these extreme transient events.

That installation manual is from Erico. Their technical library is pretty good and they do go into details if you care to explore. Another reputable manufacturer I've used is Lightning Protection International aka LPI, they too have good tutorial information.

Wal;

The inner conductor is a solid one and shield perhaps may be a tape or braided copper. Perhaps the high frequency may cause serious EM field so external conductor can prevent that by providing field gradient. That sounds OK to me. However, insulator will sure get damaged if there is lots of voltage difference to signal velocity and part of the energy will also get stored for a short time so some amount of high frequency response will be in both conductors and low frequency only in inner conductor.

I really have to try to inject signals to see how these work. I can try short impulse energy perhaps from 100kV 1us pulse.

Ok, Call me thick. Why would you want to test a coax cable when the question is for: IEC 62561-part 7 for specifying the requirements and tests for earth enhancing compounds when producing low resistance of a earth termination.

Compound being normally a material filled into a hole in the ground which aids conductivity of the earth electrode. i.e water. conductive cement, iron fillings, (to add a simple few).

Did I miss the bus on this item or did it run over my head?

In answer to the coax cable, 2 x screens, the sheath screen prevents stray EMF being induced in the cable and the inner prevents RF from escaping into other cables and equipment. Both are earthed at the ends and depending on the run length this determines whether the earthing is done at one end only, or at both ends. Short runs one end only. And please don't ask what the length is as this is determined by your system and surrounding area and equipment.

There is no way a coax can be used for earthing.

But let me know on the Compound versus testing a coax. Puzzled!

IQ;

You are right that it is deviating from the very original question.

My understanding of co-axial cable for the lightning conductor is nearly zero. I have to build that knowledge so best thing to do is to know exactly what it will do so that is the part of the experiment.

In previous discussion it was clearly stated that the shield over the lightening conductor is supposed to stop flash-over from conductor perhaps under high voltage time domain pulse which is very good information and to be taken seriously from experience of the experts else they are experts for nothing.

As lightening pulse voltage, current, time are all variables for the event, I think these safety equipment may be considering the most likely hazardous event and some cost calculation to reach out to reasonable balance between affordability and risk elimination.

A local co-axial cable capacitor will sure do some damping to the peak pulse current and that is very interesting thing. It may also break the lightning discharge at nominal voltage after conductor capacitor holds enough charge Q = CV. If V developed in the conductor capacitor is as good as space charge then lightning current in the conductor will no longer flow. This will happen only momentarily as capacitor leads are shorted so capacitor will quickly get discharged soon in less than few microseconds or even less time.

As far as ground current is concerned, earth is a big capacitor but it also has problem of charging current due to resistance. I think this lightning peak current is taken care by the co-axial capacitor which acts as an array of capacitors and along the path with LC cable damping. My concern was the TDR pulse from the place where shield and inner conductor are joined together will back fire the pulse to the top but that may not be of great concern. I am just missing that information so bothering too much about due to curiosity rather than any concern.

Standards are set after all desired knowledge and debate to reach some practical sense. I think, one can go with that unless one wants to beat the standards and there is nothing wrong in doing so. We have something called ALARA in risk management as well.

Yeh, yeh the conversation has drifted but then Shyam isn't the OP and a side discussion evolved....pretty normal for CR4.

There is no way a coax can be used for earthing.

You may think so but there are downconductors with this construction specifically designed for the purpose. The centre conductor is big. There are thousands of these installations around the world.

Have a look at the links mate and learn. Surprised me too when they first hit the market.

You are also talking (I think) about the grounding practices for coaxial RF transmission lines and there's alot more to that subject than what you barely you touched on.

As for ground resistance enhancing materials.....see my next posting.

DRIFTED! I thought the tide had come in and washed it away. The coax is normally used on antennas and I think they allow for 65kA on he screens, but this is very different to an electriacl installation for lightning protection. And they should not be confused. Quarter wave forms, higher frequencies, the antenna being a tuned circuit in itself. This is a very different protection to the everyday protection that most,(I assume here), would be used to working with.

Also, on caox systems, the coax earthing does not protect the equipment connected to the antenna, it only protects the antenna. See; Smiths Power, White Paper, Coaxial Cable Lightning Protectors.

I cannot paste the link for the paper.

Your earthing system component vendor will have these.

If he/she/transgender doesn't then select another vendor.

..and will advise on local standard compliance with approved components and sizing over the telephone as part of the sales process. GA.

The OP may want to watch this when it "airs" if he doesn't trust that reputable suppliers of ground enhancing materials are honestly complying with standards.