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To UV or not to UV

January 25, 2011

Q: 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.

A: 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 Cablecure® 732 [Ultrinium™ 732] fluid.

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.

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.

to UV or not to UV

It gets even better. The word “synergy” is overused in business circles and promised synergies are often quixotic. The poster child 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! Cablecure 732 fluid and Cablecure iXL 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 Cablecure 732 fluid, 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.