Real World I – High K

In my last post of 2011 one of my local fans, Wondering in Western Washington, questioned the veracity of the claims made by UTILX^® in a document titled, “Life Extension Estimate for UtilX^® CableCURE^® Rejuvenation Fluid.”  That document includes 17 pages and many, many claims. In this first of a series of posts, I examine the following set of claims from page 3:

Once the CableCURE^® molecule reaches those sites it performs two important functions. First, it chemically combines with the water, desiccating the water tree site. Second, it polymerizes; the polymeric chain that forms continues to grow until its chain length traps it inside of the water tree structure. Once trapped inside of the cables insulation, it serves as a “high K" style stress gradient reducing the electrical stress amplification that occurs at the tips of the water tree “branches". This two part functionality arrests the growth of water trees in aging cable.

I added highlighting to focus on the words and phrases of the claims that could create confusion; I left all puctuation and grammer errors untouched.  The first two words I highlighted could be characterized as quibbles, but I endeavor to be precise in my language. I am sure the author will appreciate my clarifications, since these claims taken together with others are held out as “irrefutable proof” of CableCURE efficacy. The third highlighted “high K” claim will receive the majority of my attention today.

Desiccating

The CableCURE molecule to which the author refers is phenylmethyldimethoxysilane or PMDMS for short. The chemical reaction of PMDMS with water is well understood. On average each PDDMS molecule consumes about one water molecule.  The effect is real, but the implication of the claim is that this desiccation-by-reaction is one of PMDMS’s two important functions.  It is not. The reaction with water is a necessary precursor to a subsequent condensation reaction. In the next sentence the author refers to this second reaction as polymerization.* Chemical desiccation is not important because the phenomenon is fleeting.  Consider the data reported by another UTILX employee in “The Importance of Diffusion and Water Scavenging in Dielectric Enhancement of Aged Medium Voltage Underground Cables” at the IEEE PES T&D meeting in Chicago, 1994.  Figure 4 and the accompanying text indicate that the water reactive capacity of PMDMS is exhausted at between 54 and 67 days for a 1/0 conductor at 60°C.  At lower temperatures the time to exhaustion might be longer, even on the order of a year or even two. When one is talking about decade-long life extension, a couple of months or a couple of years is not of critical importance. None-the-less, PMDMS does help keep the insulation dry for many, many years, but not by the mechanism suggested by the author. Instead, the mechanism is preferential wetting, which is well described in U.S. Patent 7,976,747 held by Novinium and in the paper “Advances in Chemical Rejuvenation of Submarine Cables” available here. The reason the distinction is important is that only Novinium^® brand Ultrinium™ 73X fluids include components with preferential wetting properties superior to PMDMS. Reducing the amount of water present in the insulation is indeed important, but not all rejuvenation fluids perform the same in water reduction efficacy.

Trap

The word “trap” is too absolute for this frog. Trap implies eternity and it just isn’t so.  In a December 29, 2010 post, “Chain Entanglement,” I explain how the larger oligomers substantially retard the exudation of the rejuvenation fluid, but it is not trapped. As shown in the figure nearby, improvements in rejuvenation molecules patented by Novinium (U.S. patent 7,658,808 and others pending) are designed to stick around in the insulation longer than PMDMS.

High K

There is no agreed-upon definition for High K, when applied to stress grading in power applications.  At 20°C and 60Hz, the dielectric constant or “K” of unfilled polyethylene is about 2.3 and EPR insulation varies from about 2.7 to 2.8 depending upon the specific compound. (See Bartnikas & Srivastava, Power and Communication Cables, IEEE 2000.)  The dielectric constant for PMDMS is 3.2. The dielectric constant of PMDMS is indeed higher than PE and EPR insulation, but using the word “high” is a bit of a stretch.  High K materials are quite often used in shrink-to-fit splices and terminations.  For example, 3M’s data sheet for its Quick Term II Silicone Rubber Termination Kit states:  “The High-K material has a dielectric constant of about 25.”  Pure water has a K of 78. Cyanobutylmethyldialkoxysilane or CBMDAS for short, a patented component of Novinium^® brand Ultrinium™ 73X fluids, has a K much greater than that of water.  3M’s stress control material, water, and CBMDAS are “real life” High-K materials.  I have arranged these six materials in a table nearby for easy reference.

I object to the statement proffered by the author for two reasons …

     1. It is an assertion without proof.  If the author believes that the mechanism he claims is significant with a K of just 3.3, he should provide a calculation or measurement as substantiation.

     2. The PMDMS is replacing water, which has a much higher dielectric constant.  How could that conceivably provide stress grading?  CBMDAS on the other hand, enjoys a K greater than the water it replaces.

Executive Summary

The author of “Life Extension Estimate for UtilX^® CableCURE^® Rejuvenation Fluid” is not a master of the facts. While CableCURE fluid does dry the cable and extend its life, the explanation of why this is so lacks foundation. Stress grading at the microscopic scale is possible with materials that have dielectric constants greater than the water that they replace.  One example of such a material is available only from Novinium and is protected by a U.S. Patent, other pending patents, and their foreign equivalents. While this frog cannot be sure what the author was thinking when he made his claim, I can provide a common-sense recommendation: Do not rely on secret documents that have not been peer reviewed … especially if they include assertions without proof.

Always basking in transparency,

Thermonuclear Bull Frog

*The correct terminology is oligomerization, but I will let that slide.

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.