by Thermo 25. January 2012 13:01

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

by Thermo 14. March 2011 14:56

AO, AO … it’s home from work we go

 

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 we failed 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 third of five sub-posts we will explore the role of the anti-oxidants (AO).  Every human knows the benefits of including anti-oxidants in their diets.  I am not as susceptible to oxidative damage, because I keep my temperature lower – that way I do not have to consume foul tasting raspberries and blueberries.  Besides their sickening sweet taste, the antioxidants found in berries are single-shot deals.  A single anti-oxidant molecule consumes a single oxidizer.  What we need for cables is a molecule that quenches the nasty oxidizer and then regenerates itself – indefinitely.  It would be nice for people too, but don’t hold your breath.  For cables the folks at BASF® and Novinium have a solution.

The primary AO in Novinium’s Ultrinium™ fluid formulations is BASF’s Irgastab® Cable KV10.  Furthermore all of the components of the Ultrinium UV package have anti-oxidant properties.  These materials were described in To UV or not to UV.  In the vernacular, these UV components are “two-fers” or “two-for-one” ingredients, because they fulfill at least two1 independent and important life-extension functions.

Antioxidants are included in virtually all modern cable compound formulations.  Originally deployed by polymer compound manufacturers to prevent oxidation during cable extrusion, it has been shown by

Matey and Labbe, in “Exploring the Water Treeing Inhibition Effect of Antioxidants for XLPE Insulation”, presented at Jicable ’07, the 7th International Conference on Insulated Power Cables (see pp 754-757), that antioxidants also slow the growth of water trees.  It was further demonstrated be Sekii et al, in “Effects of Antioxidants on Electrical Tree Generation in XLPE”, presented at the 2001 IEEE 7th International Conference on Solid Dielectrics (see pp 460-464), that the presence of antioxidants increases the electrical tree inception voltage.  KV10, the sulfur containing phenolic antioxidant utilized in Novinium Ultrinium™ formulations, has been demonstrated to slow the growth of water trees by a factor of four.  The class of sulfur containing phenolic antioxidants has been shown to increase electrical tree initiation voltage by up to 75% at a concentration of just 0.2%w.  KV10 enjoys a very high solubility in polyethylene and EPR, and because of its high molecular weight of 424.7, a very low diffusion rate.  The combination of high solubility and low diffusivity yields a very low sweat-out or exudation flux as was shown by Matey and Labbe.  AO can be found only in Ultrinium™ 732 fluids and Ultrinium™ 733 fluids, because it enjoys protection of U.S. patent 7,658,808, other pending patent applications, and their foreign equivalents.

Cold blooded and not oxidized,

Thermonuclear

1Ferrocene and Tinuvin® 123 are “three-fers.”  Ferrocene is an anti-oxidant (AO), an ultra-violet absorber (UVA), and a voltage stabilizer.  Tinuvin® 123 is an anti-oxidant (AO), a hindered amine light stabilizer (HALS), and a methanolic corrosion inhibitor.

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Crazy Competitor Claims | Rejuvenation Science

by Thermo 25. January 2011 17:20

To UV or not to UV

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 we failed 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 second of five sub-posts, we will explore the role of the ultra-violet absorbers (UVAs) and hindered amine (pronounced a-mean) light stabilizers or HALS.  The primary UVA is BASF®’s Tinuvin® 1130.  Additionally ferrocene (pronounced fair-O-seen), which was discussed in my last post, Voltage Stabilizer, is not only a voltage stabilizer, but also absorbs ultraviolet photons in the appropriate wave length.  In the vernacular, ferrocene is a “two-fer” or a “two-for-one” ingredient, because it fulfills two independent and important life-extension functions.

As you know, frog skin is very sensitive, and so I slather on the UVA (sunscreen) every time I am out in the sun – doing so helps keep me beautiful.  Cables buried one meter underground do not need protection from the sun’s relentless ultraviolet onslaught.  They do need UV protection, however, from UV that is created when space charges recombine near the ends of water trees.  Consider for example the work of Bamji, Bulinski, Chen and Densley in the Proceeding of the 3rd International Conference on Properties and Applications of Dielectric Materials, held in Tokyo in July 1991:

“… at points of electric stress enhancement in the polymer, the light emitted during the initiation phase of electrical treeing is … due to the recombination of electrons and holes injected into the material.  The spectra of the emitted light is in the visible and ultraviolet ranges.  The ultraviolet light can photodegrade the polymer and lead to electrical treeing.”

It is easy for us all to understand how UVA materials work.  They are opaque to UV light.  The potentially damaging UV photon strikes a resonance stabilized structure in the UVA molecule, is safely absorbed, and is converted to harmless heat.  That’s how sunscreens for our skin work too.  On my skin, if I want to stop 100% of the UV photons I need to apply unattractive zinc-oxide in a thick pasty layer – yuck!  In insulation if I want to stop 100% of the UV photons, I need to apply clay – we call those insulations EPR, EPDM, et al.  So UVA materials cannot intercept 100% of the damaging UV photons.

Unlike the common experience we all have with UVA materials, HALS are not within our normal experience.  HALS are free radical scavengers and they are beneficial, because the mechanism of photodegradation involves the creation of a free radical by errant UV photons – a photon strikes an electron and imparts so much energy to the electron that the molecule, to which it was bound, can no longer hold on to it.  A free radical (an unpaired electron in the molecule) and a free electron are created.  Electrons don’t like to be unpaired, and so, they search out other electrons and try to borrow them from their parent molecules.  As they do this, they tear apart innocent molecules and generally there is still an unpaired electron after the damage from the first encounter.  The free radical survives (or spawns a daughter) and creates cascading systemic damage.  HALS quench free radicals, and here is the cool part, they auto-regenerate to a HALS after they kill the free radical.  How cool is that?  I wish they would make HALS for amphibians, because I could take a HALS pill and snack on crickets all day without worrying about the consequences of free radicals ravaging my DNA.

It gets even better.  The word “synergy” is overused in business circles and promised synergies are often quixotic.  The poster tadpole for synergy is the interaction between UVA and HALS components.  Alone, each has a positive effect on cable life, but together they work better than the sum of their parts – one plus one equals three!  Ultrinium™ 732 and 733 fluids and Perficio™ 011 fluid utilize BASF®’s state-of-the-art Tinuvin® 123 HALS.  As we learned in the previous post, DMDB Doubts, Tinuvin 123 also stabilizes aluminum strand patina, which all but eliminates the potential for strand corrosion suffered by older injection technology.  Tinuvin 123 provides another formulation two-fer.

For over two decades, UVA and HALS have been included in TRXLPE (tree retardant cross-linked polyethylene) formulations.  See for example U.S. Patent 4,870,121, "Electrical Tree Suppression in High-voltage Polymeric Insulation,” September 26, 1989.  With the introduction of Ultrinium™ 732 and 733 fluids, Novinium delivers improved UV stabilization using the best available technology.  Novinium’s UV package is protected by U.S. Patent 7,658,808 and other pending patents and their foreign equivalents.  Only Novinium rehabilitation technology provides UV stabilization in the proper UV range.  To learn how first generation technology fails to address the UV photons created by space charge recombination, see Section 8 of the CIGRÉ Canada paper of October 18, 2010, “Cable Rejuvenation Mechanisms: An Update.”

To UV or not to UV, that is the question.  Answer:  Come out of the sunlight into the shade; live longer and with greater reliability,

Thermonuclear

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