Methanolic Corrosion of Aluminum

Inquiry

I understand that there was some issue with CableCURE^®/XL fluid when deployed in Germany in aluminum stranded cables. How do Novinium’s Ultrinium 732 or 733 fluids interact with aluminum stranded cables?

Response

It is true that about 1% of cables treated in Germany in 2002 with CableCURE/XL fluid failed because of the methanolic corrosion of aluminum. Even though the incidence of failures was quite low, the failure mode was dramatic as illustrated nearby. See the image labeled “German Cable Failure” taken from Bertini, “Failures in Silicone-treated German Cables Due to an unusual Aluminum-Methanol Reaction,” (ICC October 29, 2002). In the illustration the grey material between the strands is aluminum methoxylate, the profuse formation of which caused the insulation to bulge. The bulge is described as similar to when a snake eats a rat. An analgous phenomenon occurs in low voltage cables in the presence of water. In both cases, the bulging occurs because the aluminum hydroxide or aluminum methoxylate has a very low density, or put another way, takes up a great deal of volume. Because rejuvenation is utilized to improve the reliability of power distribution cables, even a 1% induced failure rate is unacceptable.

Novinium was founded in 2003, so we enjoyed the benefit of hindsight into the methanolic corrosion of aluminum and hence we addressed this issue in all of our Ultrinium and Perficio technologies. Novinium has not had a single incident of methanolic aluminum corrosion.

To demonstrate why Novinium technology avoids methanolic corrosion, it is useful to understand the mechanism of methanolic corrosion. One compound and one element are required for methanolic corrosion to occur … the compound is methanol; the element is aluminum.

Compound

CableCURE/XL fluid, Perficio 011 fluid, and Ultrinium 732 fluid all include methoxy silanes, which react with encountered water and produce methanol as a by-product. Ultrinium 733 fluid and CableCURE/DMDB do not produce methanol as by-products, instead these fluids produce larger, less chemically reactive higher boiling point alcohols, namely 2-ethylhexanol and n-butanol.

The reaction of methanol with native aluminum (methoxylation) proceeds at a rate proportional to the concentration of the methanol. The concentration of methanol in the strands of a treated cable is influenced by four factors:

1. The amount of water that is present in the strands and the strand-shield. Less water means less methanol; more water yields more methanol.

2. The stoichiometry of the silane water reaction. Stoichiometry is chemist-speak for the ratios at which materials react. For the CableCURE/XL fluid and Perficio 011 fluids, which utilize the same monomeric silane, the maximum possible methanol concentration is about 25% by weight. For Ultrinium 732 fluid the maximum is about 20% by weight. All other things being equal, Ultrinium would enjoy about a 20% lower methoxylation rate because of the superior stoichiometry.

3. The rate at which methanol diffuses from the strand area out of the cable. The diffusion of methanol is quite fast, so the risk of methoxylation decreases rapidly for all technologies. Higher temperature accelerates the diffusion and dissipation of methanol.

4. The use of non-methanol-based alkoxysilanes reduces methanol concentration beyond the 20% stoichiometric advantage described in factor 2 above. In a patented process (U.S. patent 7,611,748 and its foreign equivalents) Novinium adjusts the formulation with more and more non-methanol-based Ultrinium 733 fluid as the anticipated temperature of the treated cable rises.

Element

Except for copper stranded cables that are immune to methanolic corrosion, at first blush it appears obvious that elemental aluminum is available in an aluminum stranded cable, but it is not. As soon as aluminum strands are drawn and laid into a strand bundle on the factory floor, the outside layer of aluminum reacts with oxygen to form aluminum oxide (Al₂O₃). Aluminum oxide forms a dense barrier that protects the underlying native aluminum metal. This aluminum oxide layer is called a patina and it protects the underlying aluminum from further corrosion.

Patina

If you take a piece of aluminum and scrape off the patina with a knife, you will see bright and shiny native aluminum underneath. In the presence of oxygen, the patina begins to reform immediately. The shiny surface will soon return to its dull grey appearance. Of course, in a power cable there are no knives scraping off the protective patina, so how did the CableCURE/XL fluid penetrate the patina? One problem with CableCURE/XL fluid and CableCURE/DMDB is the use of a condensation catalyst called titanium (IV) isopropoxide.  Also known as tetraisopropyltitanate, we will call it TIP. Over the course of Novinium’s research we learned that TIP facilitates the degradation of the patina. Novinium does not use TIP in its Perficio or Ultrinium formulations. Novinium uses a patented catalyst (U.S. Patent 7,700,871 and its foreign equivalents) that does not suffer the same problem.

A second way that the patina can be damaged is bubble nucleation or boiling. Bubbles form in microscopic cracks in the patina and their rapid expansion and sudden disappearance mechanically perturb the patina. In the discussion above we learned that Ultrinium 732 fluids enjoy about 20% less stoichiometric methanol and hence the boiling point of the mixture is higher. Put another way, it takes a greater temperature escalation for Ultrinium to produce bubble nucleation than for CableCURE/XL and Perficio fluids. The patented silanes (U.S. Patents 7,658,808 and 8,101,034 and their foreign equivalents) included in Ultrinium fluids by Novinium and our partners enjoy improved stoichiometry, mitigating methanolic corrosion. CableCURE/XL fluid is particularly egregious in this dimension, because it includes an ingredient called trimethylmethoxysilane (TMMS) that has a boiling point even lower than methanol. To mitigate the aggressive bubble nucleation of 2002 vintage CableCURE/XL fluid UTILX Corporation reduced the concentration of TMMS in CableCURE/XL by a factor of between 3 and 6. This problem with TMMS is well documented by U.S. Patent Application 2009/0114882 and its international equivalent WO 2006/119196. Besides attacking the patina the TMMS creates a fire and explosion hazard. Novinium does not use TMMS in Ultrinium or Perficio fluids.

In addition to mitigating the causes of patina damage, Novinium utilizes a patina stabilizer from BASF^®, called Tinuvin^® 123 hindered amine light stabilizer. In experiments undertaken at Novinium, Tinuvin 123 outperformed all other patina stabilizers by at least a factor of two. Tinuvin 123 has other beneficial performance attributes to extend cable life and is included in Ultrinium and Perficio fluids and its use is protected by U.S. Patents 7,658,808 and 8,101,034 and their foreign equivalents.  In a patented process (U.S. patent 7,611,748 and its foreign equivalents) Novinium increases the supply of Tinuvin 123 by increasing Ultrinium 212 fluid as the anticipated temperature of the treated cable rises.

Summary 

Novinium substantially reduces the methanol concentration using proprietary silanes, does not use low boiling and highly flammable TMMS demonstrated to cause bubble nucleation even at moderate temperatures, eliminates a patina attacking catalyst utilized in the offending formulations, and adds a patina stabilizing compound to all but prevent methanolic corrosion of aluminum in its Ultrinium formulations. Perficio technology includes the improved catalyst and patina stabilization, and does not use low boiling TMMS. Perficio suffers from a higher methanol concentration than Ultrinium technology. Perficio technology should not be utilized in high temperature aluminum-conductor applications.

Honesty – Best Policy

Dear ample amphibian-

A gentleman from UTILX says that while he worked for Dow Corning Corporation in the early 1990’s he and his colleagues tested the materials that Novinium uses today and that Dow Corning rejected their use because these materials were second-rate, that is they did not work as well as the PMDMS (or phenylmethyldimethoxysilane), the main ingredient of CableCURE^®/XL fluid.

What say you?

California Dreamer

Dear Dreamer-

There are three assertions being made by an Individual From Competition (IFC) who knows better:

Assertion 1: Dow Corning tested the materials that Novinium uses today,

Assertion 2: The performance of those materials was second-rate in comparison to the main component of CableCURE/XL, namely PMDMS, and

Assertion 3: Even with all the other process and catalyst improvements Novinium has made, Novinium’s fluid remains second-rate.

pieces of eight

by t. b. frog

you are not the first person, to whom this dream has been spun,

i was not even a glimmer in my father’s eye when this work was done;

somebody is indeed dreaming, but it is easy to set the record straight,

consider these pieces, there are eight.

Piece One: Assertion without proof

Let’s say that you had data which demonstrated your competitor’s product was inferior to your own. Wouldn’t you publish it? IFC, come clean … show us the data you purport to possess!

Piece Two: Testimony

To get the straight scoop I went to my colleague, Glen Bertini. Mr. Bertini directed the early work at Dow Corning (circa 1992). He is the guy who conceived of CableCURE/XL fluid, and he is a co-inventor of the materials that Novinium uses today. Mr. Bertini knows that all three of IFC’s assertions are not entirely forthright. The silane materials that Novinium uses today are listed unambiguously on the Ultrinium™ 732 and Ultrinium™ 733 material safety data sheets (MSDS). These materials are …

• tolylethylmethyldimethoxysilane (+ isomer of same & 8-carbon alkoxy analog)

• cyanobutylmethyldimethoxysilane (and 8-carbon alkoxy analog)

Mr. Bertini provides a sworn and notarized declaration (link is nearby) asserting that neither of these materials were tested by Dow Corning or UTILX during the 22-year period from July 1980 to December 2001.

80-20120627_GJB_Declaration.pdf (281.40 kb)

Piece Three: Challenge

Mr. Bertini hereby challenges IFC to a public debate exploring the merits of these assertions. The debate will be recorded in its entirety and provided, unedited on YouTube for the entire world to see and hear. Novinium will bear all of the production costs and will travel to meet IFC at a venue of his choice – any time, anywhere.

Piece Four: Side-by-side taste test – Round I

IFC's employer had an opportunity to demonstrate the superiority of its technology when NEETRAC, NEETRAC’s sponsoring circuit owners, and other NEETRAC-affiliated industry leaders invited UtilX to participate in a side-by-side laboratory experiment together with Novinium. UtilX helped craft an experimental protocol, but withdrew its participation when the experiment was to actually begin. That experiment is complete and included the only rejuvenation firm willing to share their post-injection results in a truly independent experiment – that would be Novinium. UtilX demurred, citing “business and commercial reasons.”

Piece Five: Side-by-side taste test – Round II

If UTILX now regrets that it did not participate in the NEETRAC side-by-side test, Novinium will grant it a Mulligan. Novinium will eagerly participate in a new experiment, which directly compares the post-injection performance of UTILX’s products against Novinium products. It’s not too late to end the debate, but you have to promise not to withdraw at the eleventh hour this time! Novinium will fund the experiment, which will be executed by an independent laboratory with a substantially similar protocol as was previously agreed by UTILX.

Piece Six:  Analogous materials are not second-rate

It should be clear to the critical reader that Novinium’s modern fluids were never tested by Dow Corning or UTILX, but what about the second claim – the claim that the untested materials were second rate? If the materials were never tested, the assertion seems a little silly, but there is another less-than-honest dimension to this second assertion. IFC is suggesting that phenylmethyldimethoxysilane (PMDMS) utilized in CableCURE/XL fluid and Novinium’s own Perficio™ 011 fluid is first-rate or has no peers. Let’s test that assertion against the following statement proffered by UTILX in its paper, “Failures in Silicone-treated German Cables Due to an Unusual Aluminum-Methanol Reaction,” published at the IEEE, PES, ICC in October 2001. To wit …

“In those experiments there was not a statistically significant difference between the performance of methoxy silanes and their ethoxy equivalents. For example, the screening experiments included phenylmethyldimethoxysilane, tolylmethyldimethoxysilane, dimethyldimethoxysilane, and vinylmethyldiethoxysilane, which all had very similar performance profiles. The ultimate choice of the alkoxy group was not driven by performance, but was rather driven by commercial availability.”

PMDMS was chosen because it was cheap and easy to come by! UTILX names several materials for which “there was not a statistically significant difference between the [dielectric] performance” from the PMDMS that IFC now suggest is the one-and-only first-rate performer. The careful reader with some background in chemistry will note a similarity between the named tolylmethyldimethoxysilane and Novinium patented (U.S. 7,658,808 & 8,101,034) tolylethylmethyldimethoxysilane – different only in the two extra methylene units encompassed in the “ethyl.” The two materials are not identical, but they are analogous. The reported data contradict IFC’s second assertion. Novinium has done many experiments with its actual materials and these materials consistently outperform PMDMS. Check out my post of March 15, 2011 to learn how those two methylene units boost post-injection reliability of tolylethylmethyldimethoxysilane using “Chain Entanglement.” But there is more, not only are there unidentified materials in the data published by Dow Corning and reproduced in the illustration nearby, but there are materials which are not disclosed at all. Some unidentified materials performed better than PMDMS. IFC should publish all of the results – even if those results do not support his contentions.

Piece Seven:  Devil in the Details

In the illustration nearby I provide a compilation of data from the two cited sources – both are Dow Corning/UTILX documents. These data are a subset of the data to which IFC is undoubtedly referring when he makes his assertions. As you can see from Mr. Bertini’s Declaration there is even more data, which if it were made public would cast an even darker shadow on the assertions of IFC. It’s interesting data for sure, but it does not support the notion that PMDMS is particularly special. There are a variety of other materials, which show statistically similar performance. But what is the ACBD of the y-axis? It’s the AC breakdown strength (50% probability) after 6 months of immersion in ambient temperature water and 2.5X rated voltage (20 kV). Is that test protocol a good predictor of performance after 20 years? After 40? Of course, not. To suggest so would be like declaring that the horse in first place at the first turn will win the derby. The testing to which IFC refers is a short-term screening experiment and cannot discriminate long-term performance.

Piece Eight:  Overlooking the catalyst

Not only was the experiment woefully short and not thermally accelerated, all of the silanes tested were catalyzed with 0.2%_w titanium(IV) isopropoxide (TIP). Novinium does not use TIP because it suffers from an unacceptably low catalytic efficiency. It’s about 39% inefficient. Novinium’s patented catalyst technology is 98% efficient. See my previous posts on the subject of catalytic efficiency at …

Catalytic Considerations – Component I (January 3, 2011)

Catalytic Considerations – Component II (January 5, 2011)

Novinium’s master scientists have not tested every water reactive material shown in the illustration with our patented catalyst technology, but we have tested all the commercially important ones. Without exception, long-term performance, what I like to call persistence, is substantially improved by the application of Novinium’s U.S. Patent 7,700,871.

There is an old Madison Avenue adage, “If you don’t have anything to say – sing it!” Which of the following do you like the best for the IFC Corollary? (check all that apply)

ü  If you don’t have any facts – wing it!

ü  If the facts don’t support your position – obfuscate!

ü  If you won’t spend money on R&D, cite 20-year-old data out of context!

Finally, I have a selfish appeal directly to IFC, who is one of my most loyal readers. Don’t change your story one iota! The reason that so many circuit owners tell us of your tale, is that it isn’t credible. Send me your comments and I will publish them here unedited.

Credibility is transparency,

T. B. Frog

80-20120627_GJB_Declaration.pdf (281.40 kb)

Real World III – Dominion Dodge

In my last post of 2011, Wondering in Western Washington, questioned the merit of the claims made by UTILX^® in a document titled, “Life Extension Estimate for UtilX^® CableCURE^® Rejuvenation Fluid.”  That document includes 17 pages and numerous claims. In this third of a series of posts, I consider extrapolated life claims scattered across pages 13 through 15.  The author of the document presents a series of arguments built around a cable that was treated with CableCURE^®/XL fluid at Dominion Virginia Power. The 35kV, 3-phase circuit included 1000 kcm aluminum conductors and 260 mils of XLPE insulation. One phase was treated with XL fluid; another phase was left untreated as a control. The cable lies in thermic soil (12-22°C) about one meter deep with no load. In fact, the circuit has had zero load since it was treated. I will share some of the more colorful assertions by the author below, but first the context suggested by the author is that this “real world” example is representative of the population of aging cables. Presumably the reader is encouraged to assume that the measurements made on this circuit can be extrapolated to what I have taken to call, the “real, real world.”  The “real, real world” includes the 7-strand and 19-strand cables that make up the bulk of the rejuvenated cable universe. Like we saw in yesterday’s post, “Real World II – Duke Deception,” the author has not been very vigilant at choosing representative samples.

Point – Counterpoint

“This makes the result very conservative and only useful as an unrealistically low minimum boundary.”

Using very lively language the author appears to coax the reader that the analysis that follows can be applied to any case … we shall see.

“It is generally assumed that the reduction of breakdown strength over time is polymeric slowing over time. Modeling this reduction as a straight line is absolutely the most conservative approach.” 

This frog is reluctant to put words in the author’s mouth, but I believe he meant to say “a polynomial” where he said “polymeric.” Even with that correction the author is still in error. The dielectric degradation slope of solid dielectric cables is best described as an exponential decay or hyperbolic decay … but I am quibbling now. The real point of the adverb-rich language again appears to be to encourage the reader to accept the analysis which follows without undue diligence. This frog will not willingly suspend her disbelief.

“The absolute most conservative evaluation of its remaining life would be to assume that from this moment on (Time = 14 years post injection) its' decay rate is linear and equal to the decay rate of its un-injected counterpart. In other words, we assume for the sake of absolute conservatism that the fluid at this point has no effect on the cable.”

The analysis is not just conservative it is absolutely conservative. It’s difficult for me not to correct the grammar and punctuation, but I successfully restrained myself.

“Assuming that [the treated cable] will age from this point on at the same rate as its un-injected counterpart is obviously nearly ridiculously conservative. By doing so however we are able to arrive at irrefutable proof of injection effectiveness as well as absolute certainty of the absolute minimum value of added life.”

These two sentences are gems. Thinking about the meaning of “obviously nearly ridiculously conservative” is a bit like thinking about one of those science fiction time paradoxes. If I went back in my time machine and swallowed my father when he was a tadpole, how could I have ever been spawned in the first place?  What does “nearly ridiculously” mean? Almost, but not quite, ridiculous? This frog is not sure about that, but I am quite confident the author is trying to sell me an idea I shouldn’t be buying. I can be confident, because if the author actually had irrefutable proof, why would he hide it within the shroud of a “Confidential and Proprietary” document and actually sue his customer to prevent its public disclosure? (See UTILX v. City of Tacoma, No. 11-2-11594-7 in the Superior Court of the State of Washington in and for the County of Pierce.)

Fallacy of the Anecdote II

Putting aside the overenthusiastic use of adverbs and hyperbole the author makes a reasonable case for the efficacy of his product in an unloaded, 1000 kcm, 35 kV feeder cable buried in thermic soil. The problem arises because he holds out this example as one of a handful of “real world” examples and implies that these few anecdotes prove the universal efficacy of his product. The Dominion cable is not representative of the population of “real, real world” cables. In the table nearby I tally up the estimated impact of some differences between this single sample and the “real, real world.” In yesterday’s post, we saw that the Duke cable was off the mark by about a factor of 240X.  The Dominion Dodge is not nearly so egregious. Here the error is a paltry 20X-150X! The author appears headed in the right direction.

Executive Summary

If you have a cable, like the Dominion cable with no load, treatment with even low performance injection fluids should provide several decades of post-injection reliable life. However, that success cannot be extrapolated to 7- and 19-strand cables that carry cyclic loads. The old fluid utilized at Dominion Virginia Power was deployed by a Novinium founder and is available from Novinium for non-demanding applications.  Perficio™ 011 fluid works well in non-demanding applications, like cables with really thick insulation, low loads, and non-constrained conductors. In the decades since the introduction of the first generation of technology, the masters of reliability at Novinium came to recognize that one cannot treat all cables the same. Novinium is the only supplier in the world of patented technology (U.S. Patent 7,611,748) which addresses the full spectrum of cable types and sizes.

Using adverbs sparingly,

Middle East Query – Ampacity Impacts

Dweller of the Desert asked 22 questions in his post …

Middle East Query – 22 Questions.

In this installment I address question 17.

17.   Does injection have any impact on cable ampacity?

Cable injection, per se, has no effect on the cable ampacity.  Filling the small interstitial spaces between the strands with a liquid has no measurable effect.  However, the swaging technique utilized by Novinium crews and our partners is state-of-art and the terminations and splices will run cooler than those they replace.  The summary conclusions above were confirmed by testing performed by the National Electric Energy Testing, Research & Application Center (NEETRAC) at the Georgia Institute of Technology U.S.A. Click here to view the full report for NEETRAC Project Number 09-019 of April 2009, “NEETRAC Thermal Testing of Novinium Feeder Cable Splices on Service Aged 750kcmil XLPE Cable Extracted from the Georgia Power System.”

For now, Ma’a salama (مع السلامة/Good bye)

T. B. Frog

Middle East Query – Reinjection? Re-rejuvenation?

Dweller of the Desert asked 22 questions in his post …

Middle East Query – 22 Questions.

In this installment I address question 10.

1.   Can injection be carried out twice on the same cable after 10-20 years of the first injection?

When Novinium^® Ultrinium™ brand fluid is used there is no need to reinject after 10-20 years. Even in the most demanding conditions, including the hyperthermic soils of the Saudi Arabian desert, Ultrinium fluid will extend life for four decades or more. Ultrinium technology enjoys a patented Novinium innovation (U.S. Patent 7,611,748), which involves the tailoring of the fluid formulation to the specific and unique requirements of the each circuit. Older generations of injection technology such as Perficio™ fluid, which cannot be tailored to demanding hyperthermic conditions, would need to be replenished after a decade or so.  Novinium has successfully re-injected cables after 10-15 years that were previously injected with CableCURE^®/XL fluid. Novinium developed the patent pending N-Ter™ process to facilitate the re-injection of cables. Check out a case study at Littleton Electric Light in Massachusetts, U.S.A.  The procedures for N-Ter injection are available online at N-Ter™ Technology.  In short, the conductor is warmed with a low voltage current source.  The warmer conductor reduces the viscosity of the old fluid remaining in the strands and expands the conductor strands creating more interstitial space.  Innovation makes all things possible – safer, faster, better.

For now, Ma’a salama (مع السلامة/Good bye)

T. B. Frog

CableCure is a registered trademark of UTILX Corporation.

Really Long Term Life

In my December 29, 2010 post at …

Crazy-Competitor-Claims

Wonderer in the Wilderness inquired …

1. How can Novinium get the same cable life extension without a soak period?  It would seem to me that Novinium puts less fluid into the cable than one would get with a soak period.

In my first post addressing this question I provided an abbreviated answer. We learned from the abbreviated answer that that when Novinium founders conceived of the first generation of treatment fluid over two decades ago, there was a failure to check the relative diffusion rates of the phenylmethyldimethoxysilane (PMDMS) monomer and the condensation catalyst we had chosen to provide long life.  This turned out to be a grave mistake, which we have corrected.  In a subsequent post on January 3, 2011 at …

Catalytic Considerations – Component I

… I provided a more comprehensive answer, but I promised five new posts that would explain the functional improvement of the five kinds of ingredients in Ultrinium™ 732 and Ultrinium™ 733 fluids.  In this last of those five sub-posts, I explain how a component with a really ugly name provides extraordinarily long life.  Chemists call the material found in Ultrinium™ fluids cyanobutylmethyldimethoxysilane (Pronounced: Sigh-an-Oh•butte-ill•meth-ill•die-meth-ox-ee•sigh-lane); we will call it CBMDMS for short.

In the graph nearby I explain the first dimension of why CBMDMS works so well for so long.  The graph plots the “permeation product” of the three most commercially important rejuvenation silanes.  Permeation is the product of the diffusion coefficient and the solubility of the material in cross-linked polyethylene (XLPE).  The rate of fluid exudation from a cable is directly proportional to this permeation product.  Remember that if a fluid exudes out of the cable, it is not providing any life extension benefit.  The lower the permeation value, the longer the fluid will stay in the cable.  The permeation of the primary ingredient in Novinium’s Perficio™ 011 fluid and other older technology fluids is illustrated by the light-blue-colored (upper-most) line over the range of 15 to 90°C.  This fluid is called phenylmethyldimethoxysilane (Pronounced: Fen-ill•meth-ill•die-meth-ox-ee•sigh-lane) by chemists; we will call it PMDMS.  In a recent post, Chain Entanglement, I explained how extending the length of the side chains entangled the silicone in the polyethylene polymer chains and slowed the diffusion.  The orange line shows the advantage enjoyed by tolylethylmethyldimethoxysilane (Pronounced: Tall-ill•eth-ill•die-meth-ox-ee•sigh-lane by chemists) or TEMDMS, which is a result of this chain entanglement.  The permeation rate and proportional exudation rate of TEMDMS, is always lower than that of PMDMS.  At low temperature they are about the same, but at 75°C, the TEMDMS permeates about 5-times slower.  But the focus of this post is the amazing CBMDMS, which enjoys a 25-fold to 45-fold permeation advantage over the PMDMS.  That’s a really big deal!  At 75°C CBMDMS will outlast PMDMS by a factor of 45!

TEMDMS and CBMDMS are available only from Novinium, as their use is protected by U.S. Patent 7,643,977, other pending applications, and their foreign equivalents.

The cyano-group, found only in Novinium rejuvenation products, grades stress in the same way, but at the nano-scale.    Before I explain how this works we need to define a thermonuclear-sized word:  dielectrophoresis, pronounced die-EE-lek-trow-for-EE-sis or DEP for short.  DEP is a phenomenon in which a force is exerted on a dielectric molecule when it is subjected to a non-uniform electric field – the greater the dielectric constant of the material, the greater the force.  The illustration nearby explains how the diverging electrical field near an imperfection imparts a force upon CBMDMS molecules and draws them into the local-region of highest electrical stress.  The presence of the high dielectric constant material smoothes the electrical stress and interferes in several ways with dielectric failure mechanisms:

1.    The local AC stress is reduced, and water trees grow more slowly.

2.    The high electrical fields around space charges are reduced, which reduces the likelihood of UV photon creation and the inception of free electrons.

3.    Any free electrons will not be accelerated to the same energy as they would have been in a greater field.

4.    The reduced local field increases both the partial discharge inception and extinction voltages.

Greater persistence in the insulation and stress grading provide longer post-injection life even in demanding applications.  Performance at high temperature and performance in cables with constrained geometry that limit the amount of fluid that can be supplied, are greatly enhanced by the presence of CBMDMS.

Longer life through better chemistry,

Thermonuclear B.F.

Flux Weighted Temperature

In my two previous posts (“Why does load matter?” & “Projecting Future Load – Compound Growth”), I used the phrase, “Flux Weighted Temperature.”   Since we coined that term at Novinium, I have an obligation to define it.  In mass transfer, flux is the mass that flows through a unit area per unit time.  In the illustration nearby, the arrows show the flux of fluid through the cable radius as it exudes out of the insulation shield into the adjacent soil.  Exudation flux is the flux at the insulation shield outside diameter¹ and is a one-way affair.  Once fluid hits the infinite dilution of the soil, it is quickly transported away and metabolized by the flora and fauna in the soil.  The cable manufacturers call this exudation flux “sweat-out.”  Certain volatile components may sweat-out of the insulation shortly after the cable is manufactured, leaving beads of fluid on the surface.  Within the field of rejuvenation, sweat-out is not a good metaphor, because the exudation flux is so very small, there is no obvious indication that it is occurring at all.

Flux is a non-linear function (Tech translation:  That means it’s complicated!) of the dynamic temperature profile across the radius of the cable, the geometry of the cable, the materials of which the various layers of a cable are made, and the dynamic chemistry of the rejuvenation fluid.  At Novinium we use a tool, which enjoys two U.S. patents, 7,643,977 and 7,848,912, to provide accurate estimates of the flux.  We call this tool, MFlux.  I introduced MFlux in an August 3, 2010 post, “40-year Life.”

The alternative to a flux weighted temperature would be a time weighted temperature.  Assume for example that a cable spent 12 hours at a radially uniform 40°C and 12 hours at 20°C, the time weighted temperature would be 30°C.  Time weighting would lead you grossly astray, because the exudation flux, while the cable is at 40°C, is almost an order of magnitude greater than the flux at 20°C.  This is because permetion rates change by about a factor of 3 for each 10°C.  If we apply flux weighting to this example the flux weighted temperature would be 39°C [(40°C x 12 hrs x 10 flux-weight + 30°C x 12 hrs x 1 FW) ∕ (12 hrs x 10 FW + 12 hrs x 1 flux-weight)].

It is fortunate that cables do not have a radially uniform temperature profile as in the example of the previous paragraph.  If they did, treatment fluids would exude much faster than they actually do.  In fact, for all direct-buried cables with non-zero loads it is always warmer in the inner portions of the cable than the surrounding soil.  Since the solubility in insulation and shield polymers of fluids in general, and rejuvenation fluids in particular, is greater at higher temperature, the exudation flux is greatly reduced.  This is so, because the exudation flux is proportional to the difference in chemical potential or the fugacity² of the fluid in the polymer.  The fugacity gradient mitigates the inside-out concentration gradient.  Let’s take that in pieces – last piece first.  The concentration of the rejuvenation fluid in the soil around the cable is zero and has some value greater than zero inside the cable.  The concentration gradient provides a second law³ driving force for fluid exudation.  A healthy radial temperature profile reduces the chemical potential in the inner portions of the cable, but the exudation flux must still always be greater than zero.

Only Novinium can calculate the flux weighted temperature.  Only Novinium can use that knowledge to tailor the fluid delivery and fluid formulation to the requirements of an individual cable as described by U.S. Patent 7,611,748.  Only from Novinium can you learn so much from a frog!

Resting on my flux weighted belly,

Thermo

¹If there were a jacket present, the exudation flux would be at the outside diameter of the jacket.

²To learn more about fugacity in cables, check out “Molecular Thermodynamics of Water in Direct-buried Power Cables,” from the Nov/Dec issue of IEEE Electrical Insulation Magazine.

³The second law of thermodynamics provides that entropy of a system always increases.  In common language, systems become more disordered with time – if only it were not so.  The concentration of rejuvenation fluid within a cable is an ordered state, compared to the disordered state of infinite dilution outside of the cable.

Projecting Future Load – Compound Growth

Dear Thermo,

Thanks for your insightful answer in your previous post, “Why does the load matter?”  How important is the future load growth?  Our planning team gives me a range instead of a single value; they suggest 2-3%.  I have sent you some real data for several of our circuits.  Teach me oh webbed one!

Still Overworked in Ohio

P.S.  Steve is actually very helpful once you get used to him.

Dear Overworked- 

Albert Einstein is said to have once quipped, “The most powerful force in the universe is compound interest.”  He was talking about money, but the same principle applies to compound growth of any kind as you shall see if you read on.

Your planners undoubtedly consider whether the geography served by the circuit is mature or whether there is still new development likely.  On top of the growth rate from new services, how are existing customer electrical demands changing?  In general, more and more electrical applications are being deployed, but greener, more energy efficient appliances may mitigate or even reverse that load growth.  Also demand management may reduce peak loads.  I picture the planners pulling out their crystal balls to determine how fast plug-in hybrid cars will be deployed.  These are just a few of the considerations in estimating future load growth.  The impact is huge, so the exercise is well worth considering.

To test that impact, let’s do a sensitivity analysis on a single 3-phase feeder circuit, your Carrollton AM-1215.  Nearby, I have plotted estimated temperature data for the circuit for most of 2010 in 30 minute increments.  The lowest curve on this graph is the ambient soil temperature at cable depth.  The temperature of the individual cables for phases A, B, and C, are displayed as fine red, grey and blue lines respectively.  The flux weighted temperature, that is the equivalent constant temperature that provides the same permeation of fluid through a cable, are the three heavy horizontal lines using the same red, grey, and blue color scheme.  I described this process generally in my previous post and I have promised a future post to examine in more detail what flux weighting means.

The next illustration of three graphs stacked on top of each other shows the extrapolation of the Carrollton AM-1215 data with 1%, 2% and 3% annual load growth.  First allow me to explain the common elements of each graph.  The x-axis is the year.  The red, grey, and blue dashed lines are projections of flux weighted amperage for phases A, B, and C respectively.  All dashed lines are plotted against the left-y-axis.  The corresponding flux weighted annual temperatures are like-colored solid lines and are plotted against the right-y-axis.  The top-most horizontal dashed line (purple) at 603 amperes is the rated ampacity of each cable.  The lower horizontal dashed line (violet) at 469 amperes is the maximum flux weighted load.  Based upon the historical difference between the peak and flux weighted temperatures for all three phases, when the flux weighted current grows to be greater than or equal to the flux-weighted maximum load, the circuit will experience significant thermal excursions above the maximum operating temperature during periods of peak load.

In the top graph of 1% annual growth, the cable is approaching its ampacity limit in the year 2050 – 40 years from now.  All is well.  In the middle graph of 2% annual ampacity growth, constraints are experienced in about 2031 or 20 years from now.  The doubling of the growth rate halved the ampacity-life of the circuit.  In the bottom graph of 3% annual ampacity growth, constraints are experienced in about 2025 or 14 years from now.

Einstein was right – the compounded growth rate is the most powerful force in the universe!  The difference between 1%, 2%, and 3% is bigger than my belly.  For the Carrollton AM-1215 circuit, 40 years of life is simply not possible in the 2% and 3% load growth scenarios unless a portion of its load is transferred to another circuit.

If you don’t expect to keep a circuit in service for 40 years, don’t ask Steve to warrant it for that long.  Ask him for a shorter life and a discount.  The cost of the technology to obtain 40 years of life is more than the cost to reach 20 years.

Compounding my own growth,

Thermo

P.S.  As for me I have never really gotten used to Steve.  His skin lacks any camouflage pattern.  I am pleased that you have learned to look the other way.  I will endeavor to be more tolerant.

Why does the load matter?

Dear Thermo,

Why are the folks at Novinium so insistent on knowing the loading of my feeder cables?  This guy named Steve keeps asking me to estimate the load growth.  How am I supposed to do that?  The company we previously employed for rejuvenation never asked.  Is this effort really worth it?  Your NRI20 (Editor’s note:  The gentleman is referring to Novinium Rejuvenation Instruction 20, Tailored Formulation™ & Tailored Pressure™.) step 3 requires that I categorize the load into low, moderate or heavy.  How do I do that?

Overworked in Ohio

Dear Overworked-

There is a reason my first name is Thermo.  Temperature is really important!  Let’s start with a four-step chain of causality …

Chain of causality

1.    Load affects temperature.  (The cable warms as more current flows.)

2.    Temperature affects the permeation rate of rejuvenation fluids.  (Permeation rates for all treatment fluids increase by about a factor of three for each 10°C temperature increase.)

3.    Permeation rate affects how quickly rejuvenation fluid exudes from the cable.  (The faster fluid permeates through polyethylene, the faster it can sweat out of the cable.)

4.    Rejuvenation fluid exudation affects the treatment life extension.  (If the fluid leaves the cable, it isn’t helping it!)

Only Novinium’s patented approach of tailored formulation™ (U.S. Patent 7,611,748) is able to adjust the formulation and quantity of the rejuvenation fluid supplied to mitigate the aforementioned pernicious chain of causality.  That may be why the other guys don’t bother to ask.

1.    We already know where you are, so we can use the global soil regime map nearby to estimate the soil temperature at cable depth.  A larger version of the map is also at the aforementioned NRI.  For Ohio the soil is mesic and the temperature at cable burial depth varies from 8 to 15°C.

2.    Based upon your local soil thermal conductivity, provide me with the maximum design load and the corresponding temperature.  In the example that follows these values are 603 amperes and 90°C respectively.

3.    Download some historical load data for the circuit.  The data should have a date and time and load in amperes.  The data should be at least every 6 hours over a one year period, each one hour is even better.  That’s a lot of numbers, but computers excel at this and we have a MS Excel worksheet that makes child’s play of the number crunching.  We then convert the load values to approximate temperatures as shown for example in the nearby graph titled, “Current-Temp Relationship.”  In another nearby graph titled, “Flux Weighted Temperature Estimate,” four days of data are shown for the example circuit.  The historical flux weighted temperature (FWT) is thus calculated.

4.    Next you need to estimate your anticipated annual load growth over the period of the circuit's remaining life.  Don’t let the perfect be the enemy of the good.  Of course, you can’t know precisely what the future load growth is going to be, but your planning process should generate a better estimate than me sitting on a lily pad 1,933 miles away. For this example, the annual load growth is 1.2% and the circuit owner desires 40 years of additional life.

Based upon the Novinium technology embodied in a pair of U.S. Patents titled, “Predicting Performance of Electrical Power Cables,” (U.S. Patents 7,643,977 and 7,848,912) Novinium estimates the prospective FWT.  For our example, the historical FWT is about 15°C and the prospective FWT is 26°C.  The appropriate fluid choice is Ultrinium™732/30.  This cable has a low load.

As for Steve, we actually pay him to be a pest.  Please be nice to him.

Staying flux weighted cool,

Thermo

P.S. At least one of my readers is undoubtedly wondering:  What the heck is Flux Weighted Temperature?  Click on the link to learn more.

How long does rejuvenation fluid stay in the cable?

Dear Froggy,

How long do the silanes stay in a cable when they are injected?  What is the concentration of the resulting siloxanes across the radius of the insulation?

Alaskan Amber

Dear Amber-

Every single cable is unique.  First there are hundreds of possible geometries including different conductor sizes, three different strand compactions, different insulation polymers and thicknesses, jacketed and unjacked, to name a few.  On top of that there is the thermal profile of soil in which the cable is buried.  The difference between the soil temperature at one meter in depth between Alaska (Cryic soils are light blue in color in the image nearby from the U.S. Department of Agriculture.) and Arizona (Hypothermic soils are the orange color.) is about 20°C.  That 20°C makes a difference of about a factor of three on how fast the fluid permeates from the cable!  The cooler temperature in Alaska makes it easier to obtain multi-decade life extension compared to a similar cable buried in the Arizona desert.  Finally each cable is loaded differently and hence its operating temperature and temperature profile is entirely unique.  In the video, nearby, my collegue describes one of the infinite number of cases to illustrate the general idea.  Novinium has done thousands of such simulations in order to arrive at the formulations for its Ultrinium line of products.

At Novinium we use a patented process (U.S. Patent 7,611,748) to tailor the chemistry to the unique circumstances of each circuit owner and indeed to each cable.  No other firm in the world can tailore formulations to optimize performance.  Novinium does not ignore the three-fold difference between Arizona and Alaska.

Longer life through technology,

Thermo