Failure Causes III

In my January 24^th post, “Failure Causes I,” I provided a partial answer to an inquiry from Colorado Querier. Colorado sought to understand if rejuvenation technology was appropriate for the “many types of aging factors” from which his firm’s circuits might suffer. We learned that 39% or more of all circuit failures are component failures and that these reliability issues are directly addressed with a rejuvenation program.  In yesterday’s post, “Failure Causes II,” we learned that more than 78% of the cable failures, which represent over 60% of the circuit failures are directly caused by water trees.  78% times 60% yields 47%. Water trees are the root cause of more than 47% of circuit reliability issues. Taken together (39% plus 47%) component issues and water trees account for more than 86% of all circuit reliability issues. We could stop right there, because 86% could be characterized as the vast majority. We could stop right there, because of the over 100,000,000 feet of cable rejuvenated over the last two-and-a-half decades, over 99% continue to provide reliable service. Cables treated by Novinium enjoy a post-injection failure rate less than half that of the industry-wide figure. We could stop there, but we won’t. The Novinium masters of reliability strive for post-rehabilitation reliability perfection.

If component issues and water trees represent the frog’s share of reliability root causes, what are the secondary issues? And how does rejuvenation technology address, or not address, these issues?

Neutral Corrosion

The occurrence of neutral corrosion within the population of bare neutral cables is 100%.  But don’t despair, the occurrence of neutral corrosion that creates safety or reliability issues is an order of magnitude less significant than circuit failures from all other causes – that is, generally 1-2% of cables suffer substantive neutral issues. Click here to check out my July 7, 2010 post along with its links to other published works. Even though the neutral corrosion issue is less significant than many assume, the good news is that neutral corrosion is both detectable and addressable. In fact, the Novinium masters routinely detect and repair neutral corrosion.

Thermal Issues

When cables are heavily loaded over sustained periods the insulation loses anti-oxidants and plasticizers. Oxidative degradation and polymer embrittlement contribute to a decrease in dielectric strength and in severe, but rare, cases may lead to cracking of the insulation. Designed to stay in the insulation for decades after injection, Novinium’s Ultrinium™ 73X fluids include anti-oxidants (AOs) and plasticizers. These materials all but halt oxidative degradation and embrittlement. Anti-oxidants have also been proven to slow the rate of water tree growth and increase the inception voltage of electrical trees. Click here to learn more about anti-oxidants in my March 14, 2011 post, “AO, AO … It’s home from work we go.” If the insulation gets hot enough the conductor may migrate and the insulation will become eccentric. These eccentricities usually manifest themselves at tight bending radii. The Novinium masters identify and remove most excessively bent cable sections. These most commonly occur near terminations or accessible splices and these areas are inspected during pre-injection preparation. Novinium^® brand rejuvenation addresses all of these thermal issues.

Halo

Halos are unavoidable when a cable is thermally cycled in the presence of water. Thermal cycling creates micro-voids in the middle radius of the insulation driven by the “Molecular Thermodynamics of Water in Direct-Buried Power Cables.” Click here to view the paper by the same name from IEEE Electrical Insulation Magazine (Nov/Dec 2006). The collection of voids formed this way is referred to as a halo. In the absence of water trees or some other defects, a halo does not lead to failure, because the halo size is limited by the molecular thermodynamics of water in the polymer. None-the-less, rejuvenation reverses most of the dielectric degradation caused by halos by filling the micro-voids with more compatible organo-silicones. Novinium^® brand rejuvenation addresses halos.

Manufacturing Defects

Voids, protrusions, contaminants, eccentricities, and skipped shields are “unwanted features” of a new cable. With the possible exception of skipped shields all of these unwanted features are in every cable. Fortunately for your newer purchases the magnitude of the defects is low enough that the cable can provide reliable service for its design life. For both your new cable purchases and your 30- and 40-year-old legacy purchases if the defects are large enough the cables will fail early in their lives … these kinds of defects yield what statisticians call infant mortality.  Your decade-old cables have been screened by operation of substantive manufacturing defects – those that will actually cause a failure without an accompanying water tree. In short, manufacturing defects are everywhere, but in legacy cable their manifestation is a water tree growing from the defect. Rejuvenation directly address the water tree and Novinium Ultrinium™ 73X brand rejuvenation includes patented stress grading components, which directly address stress-enhancing defects. Click the links below to learn more about stress grading …

Installation Defects

Excessively tight bending radius, excessive pull force, and exterior abuse rendered during installation are analogous to manufacturing defects. Serious problems manifest themselves shortly after installation. If an installation defect survived for several decades it is not so serious that it cannot be addressed by rejuvenation technology, particularly technology that includes Novinium patented stress grading chemistry.

Physical Damage (post-installation)

Frost thrust, dig-ins, and critter attacks can occur at any time. At Novinium we have seen insect attacks and rodent attacks. Amphibians have never been a problem. In the case of critter attacks, these usually occur near terminations and hence are often discovered and rectified as a routine matter during a rejuvenation program.  Dig-ins and frost thrust are generally not discoverable, but follow a pattern similar to manufacturing and installation defects. Cables struck with significant damage fail shortly after the event, insignificant damage may be mitigated by rejuvenation. In summary, rejuvenation mitigates, but does not prevent all failures resulting from post-installation physical damage. Rejuvenation with stress grading technology such as that found in patented Novinium Ultrinium™ 73X brand rejuvenation fluids provides superior mitigation.

Testing Induced

My faithful readers know that this frog is not a devotee of diagnostic testing. The fundamental problem can be summed up thusly:  None of the technologies can reliably discriminate between cables which will fail in short order and those which will not. The rejuvenation program alternative puts a final nail in the diagnostic coffin, because components will all be changed anyway. What sense does it make to find out if the components are good or bad? Since over 99% of rejuvenated cables don’t fail when no diagnostics are utilized and the extension of life is 5-20 times longer that the retesting horizon, paying for a diagnostic is difficult to justify.  If all of that were not enough many diagnostics test induce defects! Electrical trees can be initiated directly by high voltage methods such as off-line partial discharge or indirectly by inducing space charge with DC methods. Even though it makes no technical sense to test, rejuvenation does mitigate the damage testing inflicts on cables if rejuvenation is given some time to improve the dielectric performance of the cable.  For SPR that is about a week; for UPR it is best to wait for at least a year. To explore diagnostic testing further do a key word search on my blog for “diagnostic testing.”

Insulation Shield Separation

Loss of adhesion between the insulation shield and the insulation is a rare occurrence and is the only fault mode not addressed or at least mitigated by rejuvenation. This frog can count on one front paw, and I only have four toes on that paw, the number of failures where the loss of insulation shield adhesion was the cause of failure. These few observed failures suggest that chemical contamination of the soil causes swelling of the shield material and loss of adhesion. Transformer oil or motor oil spills are suspected culprits. If you have a bunch of these kinds of failures on your hands, you have a potential Love Canal situation and you are going to be excavating the whole neighborhood.  No need to treat the cable.

Summary

Advanced cable rejuvenation provided by the masters at Novinium has a proven track record of 99.4% post-rejuvenation reliability. Almost all known causes of solid dielectric underground cable reliability problems are either directly addressed or mitigated. The sole exception is insulation shield separation, which is incredibly rare.

Broad Spectrum Reliability,

T. Bull Frog

Failure Causes II

In yesterday’s post, “Failure Causes I,” I provided a partial answer to an inquiry from Colorado Querier. Colorado sought to understand if rejuvenation technology was appropriate for the “many types of aging factors” from which his firm’s circuits might suffer. In yesterday’s post we dealt with circuit failures caused by connected components, rather than the cable itself. Today we will focus on cable failures.  First a disclaimer – it is often difficult to determine with 100% certainty the cause of a cable failure in field conditions. A cable failure is a destructive event that usually vaporizes its own root cause. Those who analyze field failures can examine the cable near its fault for neighboring defects. If a defect or defects are found, the examiner may infer without certainty that a similar defect may have been the root cause of the actual fault. If no substantial defects are found the root cause will surely remain unknowable.

I emphasized “substantial” in the last sentence because at a small enough scale there are always defects. Water trees grow in all medium voltage solid dielectric cables exposed to moist conditions. Unless you have hermetically sealed metal sheaths, those would be your cables! Water treeing is an oxidative process, but even where there are no water trees, oxidation of the polymer occurs, because oxygen and other oxidizing agents are ubiquitous. Free radicals facilitate oxidation and are common in nature. Cosmic radiation, radioactive decay, and other natural processes spawn free radicals around the clock. On top of those chemical processes there are mechanical strains placed on the cable by thermal cycling driven by load cycling.  Such thermal cycling creates micro-voids in the middle radius of the insulation driven by the “Molecular Thermodynamics of Water in Direct-Buried Power Cables.” Click here to view the paper by the same name from IEEE Electrical Insulation Magazine (Nov/Dec 2006). The collection of voids formed this way are referred to as a halo.  I provide an illustration of a halo and water tree nearby.

What are the primary causes of failure and how is each addressed or not addressed by rejuvenation?

In the frogograph nearby, I show you a subset of field reliability data (Editors note: I have come to call this kind of data – “real, real world!”) gathered by Dr. Steennis of KEMA. The simple logarithmic equation explains 78% of the relationship between maximum water tree length, expressed as a percentage of the insulation thickness and reliability expressed as AC breakdown strength.  AC breakdown strength is not a perfect surrogate for cable reliability, but it’s a pretty good one!  Lightning bolts appear next to each cable sample that failed in service. Water tree length is the single best predictor of reliability. In the same work, Dr. Steennis and his colleagues demonstrated that the laboratory failure of the field aged cables always occurred at the longest water tree, just as a chain fails at its weakest link.

Well over three-quarters of solid dielectric cable failures are caused by water trees. Rejuvenation technology was originally designed to address water tree degradation specifically. In fact, rejuvenation has a proven track record of treating the biggest and ugliest water trees on the planet.  Click here, to check out my October 5, 2011 post, “Water Trees – Too Big to Fail?” In my third post of this series we will examine the other less important root causes of cable failure and consider whether or not those root causes can or cannot be addressed by the application of rejuvenation technology.

Master of Reliability,

T. Bull Frog

Failure Causes I

Dear Beautiful Bull Frog-

I wonder if you have any information I could use to help address a concern I have heard in my company.  That concern is that a 30 to 40 year old cable may have accumulated degradation due to many types of aging factors. Cable injection may not substantially address these factors and injection may not provide a very great increase of life extension for a very old cable.

Colorado Querier

Thank you for the inquiry Colorado. That is actually a great inquiry, because it will take me more than a single post to answer! The first question we have to address is:  Which of the two categories of failures plague your solid dielectric circuits?  In the figure nearby I ponder this question, because only you can know? At Jicable 2007, the International Conference on Insulated Power Cables, Nigel Hampton of NEETRAC (National Electric Energy Testing Research and Applications Center) provided some survey data from their circuit owner members in a paper titled, “Validating cable diagnostic tests.”  Perceived failure experience of NEETRAC member companies suggested that on average, 55% of the failures in the population are cable failures, 39% are accessory failures, and 6% are unknown.  The perception of Utility 21 is that almost all of its failures are cable failures and very few of its failures are accessories. The perception of Utility 4 is reversed.  Utility 4 perceives that about 4 out of 5 of its failures are component failures and 20% or less are cable failures.

If the primary cause of your failures are components, consider which components are failing – terminations or splices or both. There are two injection paradigms, namely Unsustained Pressure Rejuvenation (UPR) and Sustained Pressure Rejuvenation (SPR). See “How to Inject” for more on UPR and SPR. Novinium is the only firm in the world that can use both paradigms. UPR attempts to flow through existing splices, so it is not the best choice if your firm experiences splice reliability issues. SPR replaces 100% of the splices and terminations with modern state-of-the-art components. UPR replaced all of the dead-front terminations, so if those are problematic components for you, UPR will address that issue. Novinium has made several improvements to the safety and reliability of dead-front terminations used for injection. I will describe those improvements another day.

In summary, if your reliability issues are primarily component issues, rejuvenation directly addressed these with systematic component replacement. Depending upon your specific circumstances, the Novinium masters of reliability will help you decide which injection paradigm best addresses your reliability issues at the lowest capital cost.

If your reliability issues are cable-centric, check out my next post in this series, Failure Causes II, where we will ask the question:  What are the primary causes of cable failure and how is each addressed or not addressed by rejuvenation?

Master of Reliability,

Thermo Bull Frog

EPR (Part 2 of 3)

In yesterday’s post, EPR (Part 1 of 3), I provided a response to the inquiry of Ethel P. Reliability on whether it made sense to rejuvenate aging EPR cables.  The short answer was yes and I dispelled some EPR myths along the way.  This post explores the chemistry of EPR and dispels another myth suggested by a physicist at the ICC meeting.  I won’t use his name to spare embarrassment, but he is often critical of others who speak without actual knowledge or evidence … a sin this frog does not commit.  The gentlemen suggested that the silanes in rejuvenation fluid might interact in some nefarious way with the silane surface treatments employed in the manufacture of EPR compounds. 

First some background

EPR or ethylene propylene rubber comes in several flavors – often designated with colors. All EPRs are roughly half rubber – the balance is filler.  Modern EPR materials use treated clays as the filler and their color varies from gray to brown to pink.  Some early EPR compounds were filled with carbon black and these are referred to as Black EPR.  Today we are going to limit our discussion to clay-filled EPR.  Those who manufacture EPR hold the details of their clay formulations close to their vests.  There are several clays including hectorite, beidellite, montmorillonite, and kaolinite.  All share several chemical properties.  All include silicon as their most prevalent low electronegative atomic constituent and all include hydroxyl groups (oxygen bonded to hydrogen represented as “-OH”).  The hydroxyl groups are connected most commonly to silicon, and less commonly to aluminum, magnesium, or lithium.  These hydroxyl groups, illustrated nearby are polar in nature and incompatible with the organic ethylene-propylene polymer. To improve the compatibility of the clay with the rubber, compounders treat the surface of the clay with silanes very similar to rejuvenation compounds. These silanes form oxane bonds, largely eliminating the hydroxyl groups. For all practical purposes these reaction are permanent – that is the silanes are permanently bonded to the clay surface. One purpose of this surface treatment is to ensure uniform dispersion of the clay in the polymer during processing. Another advantage of silane treatment of the clay filler is a reduction in the effective solubility of water in the EPR compound, because of the replacement of the hydrophilic hydroxyl groups with hydrophobic silicone. 

There is no evidence that anything in any treatment fluid interferes in any way with EPR. In fact, the opposite is true.

EPR (Part 1 of 3)

Dear Grandest of Frogs,

I was in the audience of an ICC (Insulated Conductor’s Committee) discussion group C30 (Extending the Life of Field Cables) and was confused by the discussion about treating EPR cables. There were some in the room who seemed to be of the opinion that rejuvenating EPR cables is not appropriate.  Does it ever make sense to rejuvenate EPR cables?

Regards,

Ethel P. Reliability

Dear E.P.R.-

I was not at the meeting in question, but I have several very good friends who were, so I got the straight scoop.  First there was a bizarre suggestion that those who originally invented rejuvenation technology never intended to treat EPR cable.  Two gentlemen who were actually there for the original inventive step of modern alkoxy-silane-based rejuvenation technology were founders of Novinium and are able to confirm that claim is without merit.  The target of the development effort was solid-dielectric cables – EPR cables fall within that genre.  There were several very vocal proponents of EPR cable at that meeting and they were united in a common narrative.  To wit, EPR cables do not fail, they do not suffer water treeing, and hence rejuvenation is counterproductive.

Poppycock!  Poppycock!  Poppycock! Let’s take those assertions one at a time.

EPR cables do not fail

EPR cables do fail.  One laboratory (Cable Technology Laboratory or CTL) that studies cable failures on a routine basis reports that over three decades they have received about 600 samples of failed XLPE cable and about 10 samples of failed EPR cables.  At first glance, one might say that this anecdote suggest a 60-fold reliability advantage for EPR cables over XLPE – that assumption would be exagerated, because about four-times more XLPE cable was deployed from 1964 to 1980 (See Forrest, “Predicting Medium Voltage Underground Power Cable Failures and Replacement Costs,” Western Electric Power Institute, Apr. 8, 1997).  What would be fair to say is that over the course of the last three decades, the reliability of 1960-1980 vintage EPR was about 10 to 15 times better than the same vintages of XLPE cables.  Historically more reliable, yes … invulnerable, no … in need of rehabilitation at some point, yes.

EPR cables do not suffer water treeing

It is true that imaging water trees in EPR cables is quite challenging. EPR cables are filled with clay and as a consequence even very thin samples are opaque.  Traditional microscopic examination with staining fails to reveal water trees.  A colleague at CTL has figured out a way to image trees in EPR.  Bogdan Frysczyn’s annotated images nearby show bow-tie and vented water trees right at the failure breakdown channels in so-called “pink” EPR.  Similar images have been made for brown and black EPR too.  So much for that narrative.

Rejuvenation of EPR would be counterproductive

Now that we have established that EPR cables do fail and that they suffer the same water treeing phenomenon as XLPE cables, it would seem to be self-evident that rejuvenation would benefit aging EPR cables.  Over a  decade ago, my friends over at CTL together with EPRI (Electric Power Research Institute) and Reliant Energy (Houston) wrote a paper demonstrating just this entitled, “Extending the Service Life of Ethylene Propylene Rubber Insulated Cables.”  In this paper, the authors concluded:

• It is feasible to upgrade early vintage black EPR cable and achieve a significant increase in ac and impulse voltage breakdowns.
• It is feasible to upgrade current vintage pink EPR cable and achieve a significant increase in ac and impulse voltage breakdowns.

These results were based on treatment with phenylmethyldimethoxysilane (PMDMS), which is the primary ingredient in both CableCURE^®/XL fluid offered by UTILX^® Corporation and Perficio™ 011 fluid provided by the Masters of Reliability™ at Novinium. In two subsequent posts, this frog will explain another misconception perpetrated at the last ICC meeting (EPR 2 of 3) and how the technology has advanced over the last decade to improve the post-injection reliability of EPR cables specifically (EPR 3 of 3).

Eternally Proactively Reliable,

Thermonuclear B. Frog

Deep Creep

Dear Deep Diving Frog,

I was reading a paper on your web site “Silicone Injection: Better with Pressure” that was discussing fluid pressures that different cable insulations could withstand. The testing was done at Florida Power and Light and showed that XLPE cable could withstand up to 750 PSI before bulging and approximately 650 PSI before a point of inflection was reached where deflection accelerates with further pressure increases. The pressure was increased 50 PSI every 15 minutes. Have any sustained pressure tests been performed on XLPE cables under the pressures that will be used for submarine cables, since the pressure will be sustained for months?  Also, I assume that shore ends will be a bigger concern for pressure impacts than deep water sections where the weight of the water will be pushing back on the cable?

Regards,

Concerned about Creep

Dear Concerned-

Editors note:  I had to fight my froggy urge to respond "Dear Creep."

Nearby, I have reproduced Figure 5 from the “Better with Pressure” paper, to which you refer, except I embellished it with my lovely image.  I would encourage my other readers to immerse themselves in the entirety of that paper.  First, I must make an important correction to your question.  The insulation of the cable in Figure 5 was uncrosslinked HMWPE or high molecular weight polyethylene.  Cross-linked polyethylene or XLPE has significantly better mechanical properties.  In fact, similar sized XLPE cables were injected “on-the-reel” by Hendrix Wire & Cable in the late 1980’s at pressure of 750 to 1000 psig.  See Table 1, the accompanying text on page 2, and references [5] and [6] of the “Better with Pressure” paper.

The inflection point at 650 psig is labeled as such in the figure. Up to 650 psig the difference in the inside pressure and outside pressure increased the diameter less than about 1.5% – this is less than the diametrical deflection caused by a temperature cycle to the cable’s design temperature.  However, once this inflection point is reached, polymer bonds are actually broken and the diameter change is not entirely reversible. That is, the diameter does not return to its original value when the pressure is removed. Of course, this frog would never get close to the inflection point … we stay below this point by a factor of at least three!

We have not done laboratory experiments with multi-month injection periods, but we have something even better – multi-month operational experience.  At a meeting of the Insulated Conductors Committee (ICC) on May 19, 2009, my colleague, Glen Bertini, made a presentation titled “Lessons in Submarine Cable Rejuvenation” in the C11 discussion group.  Slide 14 of that presentation describes an injection of a 14,432 foot, 1/0 compact, 25kV XLPE cable crossing Desolation Sound in beautiful British Columbia.  Desolation Sound is about 1,500 feet deep at that location.  The fluid took about 100 days, or over three months, just to reach the other end. The injection pressure was about 300 pisg. Several years later the cable remains in operation.

Willing to dive deep, but never creepy,

Thermonuclear

Middle East Query – Rejuvenation Impact on Conductor Shield

Dweller of the Desert asked 22 questions in his post …

Middle East Query – 22 Questions.

In this installment I address question 9.

9.   Will the injection affect the semicon around the conductor, since the fluid will penetrate through it?

Semi-conductive shields are carbon-black-filled polymers. Typically the carbon-black loading is about 50%.  Electrons flow through the carbon black, because the conductive carbon black agglomerates are physically touching each other.  The polymer in between the agglomerates is a dielectric. All rejuvenation fluids are quite soluble in the strand-shield. Of course, part of that solubility is because the fluids diffuse into and through the amorphous portions of the polymer. To learn how that happens, check out my 15-March, 2011 post Chain Entanglement. Even more significant than diffusion through the polymer portion is transport though the carbon black agglomerates. In the diagram nearby nano-me (my nano-sized alter ego) demonstrates the morphology of the carbon black at greater and greater magnification. Carbon black has a great deal of volume in micro-sized and nano-sized holes and pores that provide flow paths for fluid transport. Novinium fluids are selected and tested to verify that they have no detrimental effect on cable materials. Upon exposure to Novinium dielectric fluids there is a slight increase in the resistivity of the conductor shield, but well within the IEC and AEIC conductivity specifications. The agglomerate-to-agglomerate electrical connections are not perturbed in a substantive way. Novinium^® Ultrinium™ fluids include high dielectric constant stress grading components. High dielectric constant stand shields are used by at least one EPR cable manufacturer. Ultrinium fluids improve the dielectric performance of the cable system including the conductor shield.

T. B. Frog

Soaking:  Diminishing Returns I

Dear Greatest of Soakers,

It seems odd to me that for one who spends so much time soaking herself, that soaking cables is anathema to your firm’s culture.  When is it appropriate to soak a No.2 compressed URD cable?  If I do soak, for how long should I soak?

Geometrically constrained,

Alaskan Amber

Dear Amber-

You ask more questions than any of my other numerous fans.  I like that, except I have been told that some find the questions and the answers too technical.  My response to those critics is to ask your own questions.  If you ask a simple question, I will provide a simple answer.  This Amber guy is cool, his question is appropriate, and a proper answer it is going to require two posts.  Here is the first …

I can see why you might have been misled to believe that I am anti-soak, but that characterization is unfair.  Let’s set the facts straight:

1.   Novinium has a pile of patents that make soaking unnecessary, even for multi-decade life, for all but the most geometrically constrained cables.  I will define “geometrically constrained” later.  The following technological advancements, which I have expounded upon in past blogs, mean that even without a soak, Novinium technology will last longer than the two-decade old approach used by less enlightened purveyors of rejuvenation:

a.   Catalyst improvements were chronicled in Catalytic Considerations I and Catalytic Considerations II.

b.   Novinium Voltage Stabilizers are not present in older approaches.

c.    Our ultra-violet package, which retards the formation of electrical trees was laid out in “To UV or not to UV.”

d.   The tremendous power of effective anti-oxidants present only in Ultrinium™ brand fluids was described in “AO, AO … its home from work we go.”

e.   “Chain Entanglement” dramatically slows the exudation of treatment fluid from the cable and is another patented Novinium innovation.

f.     The “Really Long Term Life” afforded by still another patented Novinium innovation delivered by an ultralow permeability component.

2.   The folks at Novinium invented soaking over two decades ago.

3.   Novinium does soak cables under certain circumstances.

We do consider soaking as a last resort, however, because soaking has two drawbacks.  First, and in order of importance to us, there are safety compromises associated with leaving a hydraulic connection to an energized cable for a long period of time.  I enumerated these risks in my post:  “Greatest Rejuvenation Risks.”  For live-front applications, Novinium can greatly mitigate these risks with a piece of proprietary technology called an HVFI or high-voltage fluidic-interface.  Click here to view a HVFI test report.  Second, there are economic costs associated with a soak period.  In short, a soak bottle with an associated capital cost must be deployed for the duration of the soak period and the injection team has to be redeployed to the site to remove said soak bottle.

Despite these challenges we occasionally resort to soak periods.  The very first consideration is whether the cable to be rejuvenated has a severely constrained geometry.  The “Draft Guide for Rehabilitation and Rejuvenation of Extruded Dielectric Cable” defines constrained geometry in general and severely constrained geometry in particular as follows:

“When the available volume of fluid that can be held in the strand interstices at atmospheric pressure is less than the optimum quantity of fluid to treat the cable, the cable is said to be a constrained geometry cable.  Figure 3-1 [below] shows the three realms of geometry for round (or concentric), compressed, and compact strand cables, namely unconstrained (greater than 20 kg/km), moderately constrained (<20 kg/km and >10 kg/km), and severely constrained (<10 kg/km).”

In practice severely constrained cables are those with conductors of 7-strand and compact 19-strand construction.  If your cables do not have severely constrained conductors, four decades of life extension are possible without resorting to soak periods.

At Novinium we routinely employ soak periods on severely constrained geometry cables for high value circuits with live-front terminations.  Submarine cables provide an example of such high value circuits.  These cables can require 7-figures to replace, so the incremental cost of providing a soak is justified.  Can Novinium make soaking safe in the dead-front applications typical of residential distribution cable?  To answer that question check out my subsequent posts in this series:

Soaking II:  Safety First

Unconstrained by old paradigms,

Thermo

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.