Ten350 Web site discussion

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Joined: 6 Jan 2011 - 19:02
Ten350 Web site discussion

Introduction to Ten350 Web site discussion
This thread discusses the content on the ten350 Web site. One of the purposes of the ten350 Web site is to examine the credibility of the 10/350 current waveshape that was invented by IEC TC81 (Lightning protection) and used in standards from IEC SC37A (Low-voltage surge protective devices).

The IEEE PES SPDC has no formal connection with the people who created the Ten350 site and does not necessarily agree with the Ten350 site assertions. The SPDC is not responsible for the content of external Internet sites. This thread provides an opportunity for SPDC stakeholders to discuss the Ten350 site content and give their opinions on it.

The views expressed in user posts are solely those of the writer and do not necessarily represent official positions of IEEE PES SPDC. All postings are covered by the pes-spdc.org WARNING.

All users can view this thread and the previous 10/350 thread. To post a comment you need to be a pes-spdc.org authorized user and logged in. The process of becoming and authorized user starts at the login page and clicking "I want to create an account". All applications are reviewed, which takes time, and you will be sent a one time access link to conclude your account set up. The 10/350 can be quite an emotional subject. Should users see material they find offensive please report it with reasons to the pes-spdc.org Webmaster. Valid objections will be dealt with appropriately, by either modifying the post or deleting the posters account.

In posting material include the Ten350 page URL and the topic so that readers can review the original material. To see the latest post click the Last post button above this introduction.

Edited by: admin on 21 Aug 2013 - 08:31
Joined: 8 Oct 2012 - 23:32
Ten350 website

Old waveforms never die, they just fall to zero.

I would like to give some perspective on why the 10/350 μs waveform appeared in the IEEE C62.41 series as I was co-chair of the committee with Hans Steinhoff and editor of the standard with François Martzloff.  I believe that that a good standard separates products that perform well from marginal products through appropriate rules and good tests.  Products that pass the tests perform well in the field and products that fail the tests perform poorly in the field.  I cannot say why TC 81 adopted the 10/350 μs waveform, but I do have a unique perspective into why it appeared in IEEE documents.  I presently work for a management consultant for a MEMS company so have no vested interest in SPD designs, manufacturers or standards.

A test that replicates the field closely allows results that are easily transferred from the test lab to the real world.  In surge and lightning protection, that is difficult as the real world is very complex, random and statistical in nature, and there is little credible information about the transient nature of the problem.  The IEEE committee had used the 8/20 μs waveform for years without showing that this wave was truly representative of surges in the real world.  In fact, by the time the 10/350 μs was gaining ground, the recordings were hinting at faster rise times and longer waves than 8/20 μs.  However, applying my early logic of good standards, I left the 8/20 μs waveform in the document as it provided a test that had been failing poorly performing devices.  The tests weren’t perfect, there was a horsepower race on at the time and there were many discussions on the peak test currents, but the standard did not change in any fundamental way partly due to good products met the standard and inferior products failed the standard.  The horsepower race might have made improvements in product design or an increased lifetime, but were not necessary for the standard as a minimum level.

At the time the 10/350 μs waveform was not used in North America, but established in Europe and becoming the norm in the many parts of the world.  To ignore it at the committee level would have been foolish.  Some data was presented to show that the waveform actually existed (Dr. Peter Hasse’s work I believe) but some questioned the validity of the data.  I never cared whether it was ‘real’ or not, I was focused on releasing a good standard.  The question I had was whether good devices passed the test and poor devices failed the test.  Opinions were very strong on both sides for and against and there was little data to support either side.  The chair of the committee had taken one side of the argument so was viewed as biased.  I was very worried that the standard would stall in committee or fail to pass unless a compromise was reached.  The standard was a massive improvement over the previous standard and I did not want to lose this data over an argument that had no correct solution.  I suggested the compromise that was accepted by the committee and moved on into the standard.  It was in the annex, so not a mandatory part of the standard, and there was a 10:1 ratio placed to allow what I considered good products to pass the test.  Without the ratio I felt that products that performed well in the field would fail the test.  That would have invalidated the standard’s primary purpose.  The committee accepted this compromise and the standard easily passed the minimum voting requirements.

With the 10/350 μs waveform in the standard it was now brought to the attention of North American users and described so that testing could be done uniformly.   I felt that time would either show that good products needed to pass some form of 10/350 μs wave, or that this waveform would become more like the additional waveform that were already in the standard, but very rarely used.  Later I helped write the reality check document along with many others saying the 10x ratio was arbitrary which of course as discussed above, it was.  The IEEE standard did allow manufacturers to talk to users of the IEC standard to show that there is some equivalency and to see products into markets that were previously closed to them.

The discussions today are very similar to those a decade ago. It comes down to two questions, first; does the 10/350 μs waveform represent an actual lightning or surge event?  This question is what seemed to be the most argued with the least amount of data.  I would say the data is still inconclusive that it does or does not, but I would also say that it is not important.  The second question is; does the 10/350 μs waveform provide a test that differentiates products that perform well in the field from those that have unacceptable field performance?  That question needed time to answer so that products that were available in North America could be subjected to the test and new designs tested to this waveform.  What was done in the decade since I left the industry?  Have companies improved their designs with the test?  Have some in field problems been eliminated by the test?  Are buildings, electrical distribution systems, and end use devices better protected with this test than without? If the answers are yes than the 10/350 μs waveform and associated tests should be part of standards.  If the answers are no, then it should be tossed out as irrelevant.

Just my nickel (the penny was eliminated in Canada so I have to round up).

James Funke

Joined: 6 Jan 2011 - 19:02
Previous 10/350 activities

For newcomers it is worth pointing out that the 10/350 debate has been going on for years.

The SPDC has organised two technical sessions on the topic in the past. Presentations from the last 2006 session are to be found at:


To find the presentations navigate thus: Public> 3.0 Committee>SPDC Main Meeting Presentations.

In this folder there are six files. To save time you can download these directly from the following URLs:







There has been a long running forum discussion started in 2007 called "10/350 - Marketing ploy or useful Test Waveshape?". This, now locked, discussion can be viewed at:


Joined: 6 Jan 2011 - 19:02
CIGRE brochure 549

There has been a great deal of interest in the contents of CIGRE brochure 549 as it is one of the main pieces of evidence used by the Ten350 site. Here is a route for you to obtain a copy to make up your own mind on the validity of the 10/350 waveform. CIGRE documents have a profound influence on industry and, as a result, the recommendations are going to be conservative unless there is compelling evidence change is necessary. Measured values will have a greater weighting on decisions than estimated values from lightning detection systems.

  • Ordering instructions are on the "Search" page
    Read these carefully.
  • At the bottom of the page
    select "Brochure"
    enter "Lightning Parameters" for title
    select "2013" for year
    Click search
  • The new page lists one result 
    BROCHURE      Select   Non member price: 250 €
    549 -- Lightning Parameters for Engineering Applications

CIGRE brochure 549: Lightning Parameters for Engineering Applications (2013)
Abstract: This document is an update on previous CIGRE documents on the subject, published in Electra more than three decades ago. Lightning parameters needed in different engineering applications are reviewed. New experimental data, as well as the old data, are evaluated. Additional lightning parameters, previously not considered by CIGRE, are included. Possible geographical and seasonal variations in lightning parameters are examined. Specific applications are considered and recommendations are made.
Prices: Members 125 Euro, Non-members 250 Euro

The Ten350 site take on CIGRE TB 549 starts at

Thereafter use the arrow buttons or the list at the page bottom to see the other comment pages on CIGRE TB 549.
USEFUL TIP—Where there is underlined text, clicking on this will display an extract from the referenced source material.

Joined: 12 Jul 2012 - 08:44
Specific energy (W/R) Part 1 of 2


One of the undesirable traits of Standards Development Organisations, SDOs, is the proliferation of a term definition by needless customisation. For example, go the IEC Glossary http://std.iec.ch/glossary and type in a search for a well known term like “routine test”.

For “routine test” there are ninety one hits extracted from current standards (even more entries if you add in “routine tests”). Harmonisation would be when all the definitions are the same, but they are not all same, so definition proliferation has occurred. Some 40 % of the definitions are duplicates; most of these duplicates use the term definition in the IEV (IEC Dictionary). The rest of the definitions are mostly variants caused by customisation. Here are a few examples:

  • test to which each vehicle is subjected to during or after manufacture to ascertain whether it complies with the specified criteria
  • test carried out on all coils of the machine
  • a test to which each individual machine is subjected during or after manufacture to ascertain whether it complies with certain criteria
  • a test to which each individual transformer is subjected
  • test made on each SPD or on parts and materials as required to ensure that the product meets the design specifications

Is this customisation and consequential possible confusion necessary? The answer is no if a good generic definition exists and is known to the standards creators.

Some of better crafted definitions in the list of ninety one are:

  • test to which each individual device is subjected during and/or after manufacture to ascertain whether it complies with certain criteria
  • test made for quality control by the manufacturer on every device or representative samples, or on parts or materials or complete equipments as required to verify during production that the product meets the design specification
  • test made on each individual device during or after manufacture to check if it complies with the requirements of the standard concerned or the criteria specified
  • conformity test made on each individual item during or after manufacture

The final definition in this list is the “safe bet” as it comes from the IEV (IEC Dictionary).

But is this IEV definition as lucid as another common definition “test to which each individual device is subjected during and/or after manufacture to ascertain whether it complies with certain criteria”?

IEV 151-16-17

routine test: conformity test made on each individual item during or after manufacture

And conformity test means?

IEV 151-16-15

conformity test or compliance test: test for conformity evaluation

Very enlightening!

IEV 151-16-14

conformity evaluation: systematic examination of the extent to which a product, process or service fulfils specified requirements

Putting all that together using the IEC rule (ISO/IEC Directives Part 2 (2011) Annex D (normative) Drafting and presentation of terms and definitions) that a definition shall be able to replace its term we have:

routine test (hybrid): test for systematic examination of the extent to which a product, process or service fulfils specified requirements, made on each individual item during or after manufacture.

Obviously there are failures here to this IEC rule, in part caused by inter-definition inconsistencies e.g. “a product, process or service” in one case and “each individual item” in another. Definitions are tricky things to get totally right.

In my opinion, even worse than customisation of definitions is the inventing a new term for an existing definition, which causes a needless proliferation of terms. “Dressing up terms” and their engineering significance will be discussed in my next posting on this topic.

Joined: 12 Jul 2012 - 08:44
Specific energy (W/R) Part 2 of 2


One problem that can occur is that terms and definitions are created by experts for experts. Expert targeted terms and definitions can be very confusing to the newcomer. Experts can find it difficult to step back and create something understandable to a new engineer. This part looks at terms and definitions from a new engineer perspective and the comments will naturally seem a very picky to some experts.

Turning to the IEC Glossary http://std.iec.ch/glossary again and searching for “specific energy” yields eight hits. IEC TC81 is the IEC Technical Committee the Ten350 site is requesting action from and the two definitions reported from TC81 are:

  1. specific energy of impulse current: value resulting from the time integral of the square of the lightning current for the duration of the impulse
  2. specific energy, W/R: value resulting from the time integral of the square of the lightning current for the entire flash duration

Just the term of 1) will have the engineer doubting his education. Inductors carrying current have energy, but that energy is in the inductor not the current.

War Story

At an ILPC a well-known manufacturer was describing his triggered spark gap stating “When triggered the spark gap diverts the surge energy to earth”. An audience member raised his hand and said “Isn’t it surge current that gets diverted and not energy”. Before the presenter could formulate a reply the chairman cut in with “Correct, next slide”

Unfortunately this sort muddled thinking is far too common in presentations and documents. Using "energy" in a term just helps foster energy = current. A current doesn’t have energy. If the current flows through an object creating voltage potential difference, the object has a power loss, which over time means energy is developed in the object.

The definition part of 1) helps the engineers understanding. Put another way the quantity involved is the mean squared impulse current over the impulse period. But that’s A2s not energy. How is that energy?

The answer comes with the note that accompanies 2):

NOTE It represents the energy dissipated by the lightning current in a unit resistance

The unit resistance will develop a potential difference, have power developed resulting in energy being developed. The reason for not including the note in 2) is that Notes, Examples, etc. are informative and need not be reproduced with the definition (ISO/IEC Directives Part 2 (2011) again).

On a positive note, had the engineer looked at the definition from TC64 all would have been clear.

specific energy: energy dissipated by the lightning current in a unit resistance

With V.A. Rakov heading up the WG C4.407 group of lightning experts, I’m sure that W/R isn’t much in evidence in Technical Report 549. Lightning experts use a different term called Action Integral (∫i2dt) and it is measured in A2s. Lesser mortals dealing with mundane items like PCB track capability and fuses will instantly recognise this quantity as I2t. IEC TC32 (Fuses) created the definition:

I2t (joule integral): integral of the square of the current over a given time interval

This is the generalised version of definitions 1) and 2).

Looking at the term list we now have, specific energy, action integral, I2t and joule integral, all numerically the same for the same time interval. In detail, specific energy of impulse current is for the duration of the impulse and specific energy, W/R is for the duration of the flash.

It is a pity that the ten350 site doesn’t provide readers with more explanation on the specific energy term and the alternative terms associated with the fundamental parameter of I2t.

Even more of a pity is that we don't have one term for I2t. Perhaps some TC could use the definition of root-mean-square value (IEV 103-02-03), and create a preferential term:

mean-square value: mean value of the square of a quantity taken over a given time interval

Joined: 6 Jan 2011 - 19:02
No IEEE connection with Ten350 site

The original SPDC Newsletter announcing the Ten350 site caused some confusion as people couldn't work out if Ten350 site was connected with the SPDC. The first post of this thread states there is no connection, but the SPDC Newsletter didn't have this disclaimer. The archived Newsletter has now been updated to include a disclaimer. At our request the Ten350 site now contains the following entry in its legal statement:

The pes-spdc.org website is warmly thanked for creating a discussion forum on the TEN350 site content. But this in no way implies any endorsement of the TEN350.com website by either IEEE or the PES Surge Protective Devices Committee.

Joined: 6 Jan 2011 - 19:02
Can we really expect an exponential silver bullet for lightning?

The quick answer is no, but for those interested as to why please read on.

This thinking was initiated by a pes-spdc.org Q and i2t contribution and the “Triggered Lightning Analysis Gives New Insight into Over Current Effects on Surge Protective Devices” paper given at the XIV International Conference on Atmospheric Electricity, August 08-12, 2011, Rio de Janeiro, Brazil. The figures in this paper show that the continuing current operates the SPD for several ms after the stroke.

I take note of waveform Q and i2t values because they cause heating in the constant voltage and resistive components of the load and SPD. The ten350 site is rather dismissive of these parameters, probably because they are concentrating on the waveshape rather than its effects.

The lightning experts tend to focus on the peak current, IL, the charge, Q, and the “action integral”, A2s (as mentioned in an earlier post). This is three parameters, whereas for an exponential there are really only the two parameters of peak current, IMAX, and decay time T2. Nature being what it is, would not normally allow the effects of three parameters to be exactly matched by the two parameters of an exponential. I think at this point human ingenuity intervenes and manipulates Q and i2t parameters so that two can replace three (Reality check initiative on the equivalency of 8/20 versus 10/350 waveforms for testing surge-protective devices, F. D. Martzloff et al).

Another approach is to try and replace two lightning parameters by two exponential parameters. Ditching the lightning current amplitude and concentrating of the heating parameters means that Q and i2t values would set IMAX and T2. Using the contribution equations it can be shown IMAX = 2xi2t/Q. From which T2 = Q2/(2.88xi2t).

Taking the 100 C and 107 A2s values used to formulate a 200 kA 10/350, we get IMAX = 2x107/100 = 200 kA with a T2 = 1002/(2.88x107) = 347 µs. QED In fact, you could take any two of the three parameters and get the same result, which seems an engineering unnatural.

To get the overall heating effect the lightning flash parameters are needed. Flash parameters take into account both the impulse and the continuing current components. The 1 % flash distribution values from the “Current waveforms for lightning simulation” by Gamerota et al are used here.

Negative flash (160/56 kA peak, no duration given)

280 C and 5x106 A2s gives IMAX = 36 kA and T2 = 5.44 ms

Positive flash (350 kA peak, 85 ms duration)

910 C and 20x106 A2s gives IMAX = 44 kA and T2 = 14.3 ms

Compared with the values that created the 10/350 the positive flash charge is nine times greater and the i2t is two times greater.

Had the 50% flash distribution values been used, for the negative flash (32/11 kA, no duration given) IMAX = 7.2 kA and T2 = 2.4 ms and for the positive flash (35 kA, 85 ms duration) IMAX = 5 kA and T2 = 16.7 ms.

One thing that hasn’t been played in here is the thermal time constant of the voltage limiter. A very large thermal time constant would have the full heating effect of the above, while a short thermal time constant would have a chance to cool between strokes. Also as the peak currents are lower, the voltage increase and consequent heating at the real lightning peak current levels are not comprehended.

For a given technology one could use any impulse, say 8/20, provided the rated peak current value correlated with acceptable field performance. The Ten350 site suggests a 160 kA, 8/20 value in one place. But it would be misguided to apply the same current rating to a dissimilar technology.

If one were to try and emulate real lightning the test would have to provide single and multiple impulses combined with a continuing current. The reported test with multiple impulses was missing the continuing current.

Joined: 6 Jan 2011 - 19:02
Study of Gamerota paper

The large disparity in the charge between the stroke value given by Gamerota and the 10/350 formation lead me to study the Gamerota paper further to find a reason.

The paper title is “Current Waveforms for Lightning Simulation” authored by W. R. Gamerota, J. O. Elisme, M. A. Uman and V. A. Rakov. Uman and Rakov are internationally recognised lightning experts and Rakov lead the group of experts who created the CIGRE TB 549.The Gamerota paper appears in the IEEE Transactions on Electromagnetic Compatibility, Vol. 54, No. 4, August 2012. For a modest sum (nothing if you are an EMC society member) the paper can be purchased from the IEEE, just go search on the title and ye shall find.

As usual the stroke (impulse) and flash (everything including the continuing current (CC)) are treated separately. For the 1 % positive flash, the values are:

Stroke: 350 kA, 40 µs duration to 50 %

Continuing current: 30 kA, 890 C, 85 ms duration to 7 %

Flash: 350 kA, 910 C, 20x106 A2s, 85 ms duration to 7 %

From this one concludes most of the flash charge comes from the continuing current. Gamerota shows the continuing current as an exponentially decaying current with a decay time of about 22 ms. The calculated charge is Q = 30 kA x 22 ms x 1.44 = 950 C, a negligible 7 % increase in the specified value of 890 C. The i2t will be 0.721 x (30 kA)2 x 22 ms = 14x106 A2s. The immediate problem here is that 70 % of the flash i2t comes from the continuing current, only leaving 6x106 A2s for the stroke.

Let’s go at this in two ways as a sanity check.

Using the Gamerota values of 350 kA and 40 µs, we get Q = 1.44 x 350 kA x 40 µs = 20 C and i2t is 0.721 x (350 kA)2 x 40 µs = 3.5 x106 A2s. The calculated charge of 20 C is the same as to the flash and continuing current difference (910 – 890 = 20). There is a 70 % disparity between flash and continuing current i2t difference and the calculated i2t from the stroke duration.

Using the calculated stroke i2t, 6x106 A2s, and the 350 kA amplitude the effective duration of this is 6x106 A2s / (350 kA x 1.44) = 70 µs. That in turn would give a charge of 35 C.

To emulate the flash situation two simultaneous exponentials would be required

  1. 350 kA somewhere between 40 to 70 µs duration
  2. 30 kA of 22 ms duration

Getting back to the large disparity in charge between the stroke value given by Gamerota and the 10/350 formation, one can point out the 10/350 formulation cuts off the charge at 10 ms whereas Gamerota runs out to 85 ms plus.

Let’s see what the values would be for a 10 ms truncation of Gamerota’s values. The cumulative build up of Q and i2t for an exponential decay is shown here in clause B.13. For 10 ms, the continuing current has about 50 % of the i2t developed and about 25 % of the charge. This gives

Continuing current: 30 kA, 7x106 A2s and 240 C

Stroke: 350 kA, 6x106 A2s and 35 C

Summing charge and i2t gives

Summation 350 kA, 13x106 A2s and 275 C

For charge the single exponential duration would be 550 µs.

For i2t the single exponential duration would be 150 µs.

One cannot satisfy both charge and i2t using a single exponential.

Not surprising as Gamerota, Elisme, Uman and Rakov conclude with

“While it is possible to simulate either measured flash charge or measured action integral exactly (i2t), the other parameter will then not necessarily be well simulated; therefore, compromises are made to simulate both to reasonable approximation.”

For situations where the charge is the most important parameter the single exponential duration should be set to deliver the appropriate charge. For situations where the i2t is the most important parameter the single exponential duration should be set to deliver the appropriate i2t. A compromise duration will under test one parameter and over test the other parameter. As shown earlier both charge and i2t can be more accurately simulated with two exponentials for the positive flash.

Obviously the same exercise can be done for the negative flash. However, multiple stroke impulses would be required to comprehend the thermal time constants of the items that the current flows through.

Joined: 6 Jan 2011 - 19:02
Gamerota et al on negative flash

Negative Flash Parameters

Having looked at the positive flash from the Gamerota et al.: Current Waveforms for Lightning Simulation paper, I thought looking at the lesser stress negative flash would be interesting. The negative flash recommended values did not correlate as well nor were as definitive as the positive flash recommendations. As a result there is some “artistic licence” used in this analysis.

The severe negative flash parameters are measured as:

Q                                             = 200 C

i2t                                            = 3x106 A2s

modelled subsequent strokes = 15

160 kA peak exponential decay times for this amount of Q and i2t would be 880 µs and 170 µs respectively

First negative stroke

Peak current    = 160 kA

50 % duration= 80 µs

Q                     = 27 C

Q (calc)           = 18 C

i2t (calc)          = 1.4x106 A2s

Charge is probably a better parameter than duration. To get the 27 C value would require the duration to be 120 µs, a 50 % increase. A duration value of 120 µs would give an i2t (calc) of 2.2x106 A2s

Subsequent negative strokes

Peak current                = 56 kA

50 % duration            = 35 µs

Q (calc)                       = 3 C

i2t (calc)                      = 0.08x106 A2s

15 stroke Q (cal)         = 42 C

15 stroke i2t (calc)      = 1.2x106 A2s

(If the same 50 % duration increase as for the first negative stroke as applied, then this gives a 15 stroke Q (cal) of 63 C and a 15 stroke i2t (calc) of 1.8x106 A2s.)

Negative continuing current

Peak current    = 1 kA

50 % duration= 50 ms

Q                     = 69 C

Q (calc)           = 70 C

i2t (calc)          = 0.07x106 A2s



The continuing current does not substantially contribute to the flash i2t, but with a Q of 69 C it is 35 % of the flash Q.

The combined negative stroke charge is 69 C, leaving 62 C of the 200 C flash charge unaccounted for.

To emulate the negative flash, one could use a 160 kA, 170 µs (40 C) exponential impulse for the flash i2t value combined with a 1 kA, 110 ms (160 C) exponential impulse to provide the bulk of the flash charge. The end result is something like a 200 C, 3x106 A2s stress. The failing of this approach is the single, rather than multiple; stroke emulation would not test protectors with short thermal time constants correctly.

For comparison, the positive flash dual exponential emulation was 350 kA, 40 µs to 70 µs and 30 kA, 22 ms duration. The end result is something like a 910 C, 20x106 A2s stress.

The 10/350 result at 350 kA would be 18 C and 31x106 A2s, delivering only 2% of the flash charge and 55 % more i2t than the flash.

Joined: 8 Oct 2012 - 23:32
Source and Relevancy of 10/350 Waveform

Here's a dialog between the Chairman of the SPD Committee and myself concerning the origin and relevancy of the 10/350 waveform.  

Best regards,  Bruce


Dear Tony,

Thanks for reminding me of your 2007 post on the 10/350 waveform.  I'm putting the URL here so that our fellow TAG members can access it and also read the follow-on post post from M. Maytum which blew the whistle on the conflict of interest and shenanigans of Dr. Hasse and the earlier TC 81 membership.    http://pes-spdc.org/content/10350-marketing-ploy-or-useful-test-waveshape 

Your post starts off by making the point that the 10/350 waveform does not represent a direct lightning discharge.  And in that you were perfectly correct.  But unfortunately you followed that with the assertion that the 10/350 waveform " is not intended to represent the lightning discharge per se, nor is this claim made within the IEC standards community. "   

The falsity of that allegation is documented in great detail on the TEN350.com website.  Dr. Hasse, while a member of TC 81, and Managing Director of Dehn, apparently engaged in a multi-million dollar propaganda campaign (still in progress, by the way) to persuade us that indeed the 10/350 waveform DID represent the lightning discharge.  There are at least 8 pages that deal with this issue starting at this URL: http://www.ten350.com/index-7-hasse.html.

And Tony, I think  in your heart you were aware of this because right in that post, just a few sentences later you wrote:   "The 10/350 wave shape is used within IEC standards when a conductor (or SPD), is expected to carry direct or partial lightning currents."  

I'd like to address just one more point from your post.  You wrote that the 10/350 waveform "replicates the longer tail of the lightning discharge."  And that it represents " a worst case scenario."  Says who?  That is the question to ask.  Says WHO?  The earlier TC 81membership answered this question clearly.  They said Berger and CIGRE.  

And that's what makes the new CIGRE report  #549 so relevant.   TC 81 can no longer claim Berger or those early CIGRE articles to be the source of the 10/350 waveform, the length of the tail or the worst case scenario.  What's more, the CIGRE Report 549 provides new answers to questions like  "how long a wave tail,"  "what worst case scenario," "how important are multiple impulses," etc.

The TEN350.com website documents these various issues in great detail.  

At this very minute electronic equipment is probably being burned somewhere because of the injection of the 10/350 waveform into international lightning protection standards.  This is also addressed in the TEN350.com website. http://www.ten350.com/index-10-damages.html

You state you are confused about the purpose of the TEN350.com website.  Possibly you missed that page.  Here's the URL:  http://www.ten350.com/index-2-about.html

In fact, the TEN350.com website is fostering the most constructive and fundamental discussion concerning the 10/350  waveform and the international lightning protection standards  that we've had in a number of years.

Sure, we could hold on to the 10/350 waveform for another 20 years, kick the CIGRE report under the rug, pretend it doesn't exist, and lambast the TEN350.com website as the work of kooks.   

That would be the easier course, but we won't because that's not what engineers do.

Best regards,

Bruce Glushakow

On Aug 20, 2013, at 8:16 PM, A.J. (Tony) Surtees wrote:

Dear Bruce,

> Thanks to Tony Surtees for establishing a facility where all stakeholders are able to voice an opinion.  The link to the forum on thepes-spd.org website is:  http://pes-spdc.org/content/ten350-web-site.  The link on how to become an authorized member of the forum is on the home page of the ten350.com website.  TAG members and TC 81 members alike are invited to participate.

Since my name is mentioned here I wish to clarify any misconceptions which may arise in the minds of those copied.

·         The IEEE SPDC 10/350 posting site was setup in 2008 to foster constructive discussion on the subject of the 10/350 wave shape within the SPDC community. This followed from a forum held the previous year when Mr. Hubert Bachl and myself presented the case for the 10/350 wave shape based on its adoption in IEC SC37A and IEC TC81 respectively. It was not established to facilitate the new TEN350 site.
·         As chairman of IEEE SPDC I have in the last week received a number of comments and concerns perceived linkage between the TEN350 site and the IEEE SPDC. I took action last week to request that our web administrator to distance our SPDC site from any perceived endorsement of the material on the TEN350 site. Thank you for assisting him in this matter.
·         On a personal level I share the concerns expressed by Mitch Guthrie and am unsure of the intent behind the new TEN350 site. Our LP industry is not served well by such polarizing sites (and there are others) which create dissent rather than harmonize. International standards will always have elements of scientific and commercial interest. Both are important aspects in arriving at a good standard. I do not believe the 10/350 wave shape is a “hijack” by any one of these interests.    
·         I suggest your site would find some balance by posting the attempt made to explain the use of the 8/20 and 10/350 wave shapes in my posting “10/350 Marketing ploy or useful Test Waveshape?”. The title I chose was to address the criticism often leveled by opponents to this wave shape, and ultimately gave title to the SPDC site you mention which was setup to discuss it.
·         I trust an open minded read of the paper leads to the same conclusion the paper ends with: “Can we live with an 8/20 wave shape and a 10/350 wave shape? Both 8/20 and 10/350 are useful and important in the characterization of different aspects of an SPD. 8/20 is used to characterize the voltage protection level of the device and its mechanical properties (higher dv/dt), while 10/350 looks to characterize the behavior of the device in conducting large charges which flow for longer durations. In summary: one is not more important than the other, they are just useful in different ways.”

Tony Surtees