by Thermo 27. September 2013 19:38

Supersaturation

Inquiry

Under what circumstances does supersaturation or over-saturation occur in rejuvenated power cables? Do supersaturation or over-saturation cause cables to fail?

Response

I think we all have experience with supersaturation. What kid didn’t make rock candy? Warm water can dissolve more sugar than cold water. As the temperature of sugar-saturated hot water falls, the sugar becomes supersaturated and it will crystallize out of solution onto a seed crystal on a stick. The result is a pure-sugar treat in an attractive crystalline form.

Cable engineers need not look back to their childhood for examples of supersaturation, because water halos are a phenomenon that occurs in all polyethylene power cables subjected to thermal cycling. In the photograph nearby the circular halo is visible along with the vented water tree. The formation of the halo is explained in “Molecular Thermodynamics of Water in Direct-Buried Power Cables” (IEEE Electrical Insulation Magazine, Nov/Dec 2006, p. 20), Bertini explains how halos form:

“When the temperature decreases [in a cable], the thermodynamic driving force reverses, and the water is driven out of the PE and out of the vapor phase within the voids to the liquid phase. If the water molecule is close to the outer cable surface, it can exit the cable into the soil. If the water molecule is close to a stranded and unblocked conductor, it can exit the polymeric layers and enter the strand interstices. However, if the water is near the center of the insulation, the water cannot exit the insulation fast enough and the insulation becomes supersaturated with water. If a solid-core or effectively strand-blocked conductor is used the region of supersaturation is likely expanded radially inward. The water phase creates a large number of voids near the center of the insulation that are collectively referred to as a halo …”  Click here to see the entirety of the paper.

Supersaturation of water occurs in nearly all power cables and does not cause a cable to fail. The reason that water supersaturation does not create a serious reliability issue is that the solubility of water in the polyethylene is very low. In order for there to be a reliability issue associated with supersaturation, three elements are required.

1. The cable must undergo substantial thermal cycles. Thermal cycles are greatest when the amplitude of the change is large and the frequency of the change is short.

2. There has to be an excess supply of the soluble fluid.

3. The solubility of the fluid must be sufficiently high at higher temperatures.

Thermal Cycles

If cable load stays below 50% of the cable ampacity the risk of over-saturation is close to zero. In order to drive over-saturation large temperature swings are required to occur within a 24-hour period. Such swings are rare in typical underground residential distribution environments, but are much more common in large conductor feeder cables.

Excess Supply

U.S. Patent 6,162,491 conceived and reduced to practice by a Novinium founder, defined the relationship between the amount of fluid required to properly treat a cable and the amount of fluid reservoir that is available within the cable strands. The graph nearby summarizes the relationship for all conductor sizes and for the three most common strand compressions. For any given conductor, where the interstitial fluid quantity is less than or near the fluid requirement the chance of over-saturation is very close to zero. At Novinium it is zero, because Novinium technology does not require a soak period. Other suppliers leave soak bottles attached to the cable for months that run the risk of over-supply if the field technicians do not properly limit the size of the reservoir.

For conductors larger than 500 kcm (about 250 mm2) that are not compact conductors, the volume in the strands is greater than the amount of fluid required to treat the cable. In this case over-saturation is possible if the other two elements are present, namely Thermal cycles discussed above and Solubility discussed below.

Solubility

 There are three solubility classes of alkoxysilanes used to rejuvenate power cables.

 

Alkoxysilane Class

Commercially Significant Examples

Solubility

g/cm3 @ 80°C 

Alkane

dimethyldibutoxysilane predominant component of CableCURE®/DMDB fluid

 0.41

Cyclic-aromatic

phenylmethyldimethoxysilane predominant component of CableCURE/XL fluid and Perficio™ 011 fluid

 0.15

tolylethylmethyldimethoxysilane significant component of Ultrinium™ 732 fluid

 0.15

Cyano                 (pronounced sigh-an-oh)

cyanobutylmethyldimethoxysilane significant component of Ultrinium™ 732 fluid

0.014

The greater the solubility, the greater the risk of over-saturation. Consider the case of the Alkane class of materials. At 80°C polyethylene swells over 40% in the presence of excess Alkane fluid. A 40% swell places substantial mechanical stress on the cable and the risk of catastrophic failure is relatively high. Novinium utilizes only low concentrations of these materials to avoid the risk of over-saturation.

The Cyclic-aromatic class of materials enjoy almost 3-times less solubility, and hence the conditions required to create a problem are about 3-times more severe. Even though supersaturation is a rare event with Cyclic-aromatic materials, Novinium does not recommend their use where the temperature of the cable might be above 40°C unless they are utilized with a lower solubility buffer such as a Cyano class material.

The Cyano class of materials is an order of magnitude less soluble than the Cyclic-aromatic materials and the chance of over-saturation is nil. Novinium is the only firm in the world that can practice the technology of U.S. Patent 7,611,748 to tailor a rejuvenation formulation to the cable. One of the key parameters that we tailor is the ratio of Cyclic-aromatic and Cyano class materials to the thermal condition expected of the cable to be treated. The higher the temperature and the greater the temperature cycling, the greater the ratio of Cyano class materials to Cyclic-aromatic class materials.

Summary

Failure due to over-saturation is a pretty rare event, even with legacy approaches. Novinium avoids Alkane class materials and utilizes formulation tailoring to stay well away from the conditions conducive to over-saturation. At Novinium our failure rate due to over-saturation is zero. Our overall failure rate from all causes is less than half that of legacy technologies.

Reliability through better chemistry,

TBF

by Thermo 26. September 2013 21:00

CO2 v Helium

Dear green-one,

Novinium and UTILX use different gases to push their fluids, CO2 and helium respectively. UTILX also uses nitrogen to flow and pressure test the cable. Why the difference? Is there a benefit of one over the others? Does the CO2 contribute to global warming?

Query from Canadian Capital  

Dear Cap-

There are safety, environmental, and economic benefits of using CO2.

Safety Benefit

Effervescence limits the conductivity of fluid effluent along the vacuum tube interior. Carbon dioxide (CO2) is liberated when you open a soda or beer bottle, because the pressure on the fluid is released.  CO2 is used in iUPR (improved Unsustained Pressure Rejuvenation) to provide the driving force to the rejuvenation fluid. CO2 is even more soluble in Ultrinium™ and Perficio™ rejuvenation fluids than it is in beer and soda. As CO2-saturated rejuvenation fluid flows through the strand interstices and down the length of a cable the absolute pressure decreases almost linearly along the cable length. As the pressure decreases CO2 is liberated. The viscosity of gaseous CO2 is orders of magnitude lower than the liquid phase from which it effervesces, so it bubbles ahead of the fluid and rushes to the vacuum tank. Any fluid exiting the cable is interspersed between much more voluminous CO2 bubbles. Of course, gaseous CO2 is a great dielectric and its presence disconnects adjacent droplets of fluid and prevents there being a contiguous path for current to flow. Water, if present, does not wet the surface of the polyethylene tube, but instead stays as discrete droplets. The conductor voltage is not efficiently conveyed along the tubing length, greatly reducing the possibility that a collection bottle will become energized.

Environmental Benefit

Paradoxically the use of CO2 delivers lower net CO2 emissions. The primary industrial sources of CO2 are waste streams like the flue gas of fossil fuel power plants and CO2 contaminated natural gas.  If the CO2 were not captured by the suppliers, it would be vented to the atmosphere.  There is no net CO2 created.  It takes energy to provide pressure to inject fluid through a cable.  Energy invariably means more net CO2.  It takes 8-times more energy and 8-times more CO2 to make a standard cubic foot (SCF) of N2 than a SCF of CO2.  It takes 15-times more energy and 15-times more CO2 to make a SCF of Helium than a SCF CO2.  Not only is CO2 the most CO2-efficient gas, but the advanced Novinium process uses a lot less gas than the older injection approach.  First the older approach requires air flow and pressure tests using compressed nitrogen (N2).  Novinium uses flow and pressure tests less than 10% of the time, and when we do, we use CO2.  The older approach uses helium (He) as a fluid driving force in its feed bottles, Novinium uses CO2.  Not only does the use of helium have the adverse global warming impact resulting from the large amount of CO2 used to produce it, but helium itself is a scarce world resource.  Of course, compared to the replacement alternative, rejuvenation has a huge net benefit to global warming.

 

Economic Benefit

CO2 is less costly and because it is delivered in cylinders as a liquid there is less effort required by our field teams to maintain a supply. Cheaper – safer – more earth-friendly!

It’s easy to be green,

TBF

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Envirnomental Inquiries | Safety Matters

by Thermo 19. September 2013 17:04

Methanol Matters

Dear Famous Frog,

Methanol is both poisonous and explosive. What precautions will be taken by the circuit owner or Novinium if the cable, cable components, or injection equipment were to leak Ultrinium™ 732 fluid and mix with water (i.e. flooded vault scenario)?

West Coaster

 

Dear Coaster-

First let’s chat about the word “explosive.” Flour is explosive if you mix a bunch of flour with air in just the right concentration. I suspect you have flour in your house, but I doubt you keep it in an explosion-proof cabinet. Analogous to the flour in your home, the methanol that is liberated by the reaction of methoxysilanes (The predominant class of materials employed to rejuvenate URD cables and including Ultrinium 732 fluid) has an extremely low explosion risk. I’ll explain why that is so later.

Next, let’s talk about the word “poisonous.” Methanol can be found in your garage. Methanol is typically 30% to 50% of the blue windshield washer fluid used in your automobile. There are two primary precautions to avoid methanol poisoning. The first precaution is to not drink the water in your flooded vault scenario. That’s good advice for a host of reasons. The second precaution is to avoid breathing methanol vapors. This is easily achieved by ventilation of vaults before humans enter. When present, methanol vapors register with the devices commonly utilized to test the safety of air before people enter a confined space. In unconfined spaces, natural ventilation will keep the methanol concentration very low. There is methanol in wine and apple juice, so small quantities are not at issue. If somebody smells a strong solvent-like smell the space should be exited. To reduce the methanol concentration increase the ventilation, remove the spill with a vacuum truck or other means, and/or dilute with more water.

There are four reasons why methanol is not a particularity great explosion or poison risk with Novinium® brand rejuvenation:

1. Novinium’s preferred injection method, sustained pressure rejuvenation or SPR does not involve unattended feed tanks. In the unlikely event that a leak does occur it can be stopped quickly, limiting the magnitude of the spill. SPR is a patented process available only from Novinium. The patented injection adapters (IAs) used at the cable ends are extraordinarily robust and unlikely to leak. The cable itself cannot leak unless it fails dielectrically. Failure with SPR occurs in fewer than 0.2% of treated cables. In the event of a dielectric failure only a small amount of fluid is likely to leak. The amount of fluid that can leak depends on the size of the cable and how long prior to the failure the cable was rejuvenated. Rules of thumb to estimate leak size are available in Novinium Rejuvenation Instruction 99, Cutting a Treated Cable (NRI99). For a typical URD cable the spill size is most likely less than a cup of coffee.

2. When the second-best approach is utilized, improved unsustained pressure rejuvenation or iUPR a feed tank is typically left attached to the cable for about 24 hours. There is no soak period. A soak period involves the use of soak tank reservoirs for multi-month periods. The exposure to a potential leak with iUPR is typically 60-times less than the 25-year old unimproved-UPR technology. “iUPR” is made possible by Novinium patented technology.

3. Methoxysilanes react slowly with water to liberate methanol. The speed of this reaction is limited by two main factors. First, alkoxysilanes are not appreciably water soluble so a spill into water creates two liquid phases – like vinegar and oil. The reaction occurs primarily at the phase interface – this slows the evolution of methanol. Second the reaction is naturally slow – full reaction would occur over the course of hours. The volume of methoxysilane, such as Ultrinium 732 fluid, used to treat cables is very small. For example, 19 strand cables require less than a gallon to treat 1000 feet. In your “flooded vault scenario” there will likely be many, many gallons of water and any methanol formed is quickly diluted in the water. The volume of patented Ultrinium fluids required to treat cables is typically about 30% less than the volume required by older approaches.

4. Methanol is very soluble in water – in fact water and methanol are infinitely miscible. When methanol is mixed with water its vapor pressure is greatly reduced as is its toxicity. In other words, water mitigates methanol issues with all Novinium technologies. The more water the better. Unfortunately the flammability and explosion risks associated with CableCURE®/XL fluid are not mitigated by water, because that material includes a highly flammable material, trimethylmethoxysilane (TMMS), that is not water soluble. For a thorough discussion see Flash Point Matters.

Safer is better,

TBF

 

CableCURE is a registered trademark of UTILX Corp.

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Safety Matters

by Thermo 21. May 2013 21:31

Shields Scotty

Inquiry

What impacts do rejuvenation fluids have on the conductor and insulation shields?

Response

With Star Trek Into Darkness in the theaters it was appropriate to revisit the question of shields. Not the shields that deflect Klingon disrupter blasts, but the conductor and insulation shields used to smooth electrical stress in underground power cable. When rejuvenation technology was first introduced about 25 years ago, that was one of the first questions that had to be resolved.

The table below provides some publically available data from a report prepared by Cable Technology Laboratories titled “Testing of VEPCO 35kV cable 5 Years After Upgrading,” dated May 28, 1999. The data examined the impact of a 70:30 mixture of phenylmethyldimethoxysilane and trimethylmethoxysilane (the white phase) and dimethyldimethoxysilane (the blue phase) in an application at Virginia Electric Power, compared to the untreated control (the green phase).

In short, both rejuvenation fluids show slight, but insignificant increases in volume resistivities of the conductor and insulation shields, four year after treatment at both 22°C and 90°C. In all cases, the increase is well below the limit set for cables of that vintage. The more modern limit is even more forgiving than the 1971 values. Dozens of such measurements were made in the last century, but they ceased to be interesting, because the impact was repeatedly insignificant.

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Rejuvenation Science

by Thermo 2. April 2013 15:32

Between Orange and Lemon Juice

Wikipedia defines “Fear mongering (or scaremongering or scare tactics) [as] the use of fear to influence the opinions and actions of others towards some specific end. The feared object is sometimes exaggerated, …”

The “feared object” is Novinium’s patented acid catalyst. U.S. Patent 7,770,871 (together with its foreign equivalents) demonstrates the tremendous benefits of this leap forward in rejuvenation technology. This advance, patented on April 20, 2010, largely makes the previous generation of technology irrelevant. So naturally the tactic of fear mongering is utilized by the purveyors of the over two-decade-old approach. 

The purpose of this post is to explore whether one should be concerned about the patented acid catalyst in Novinium brand Ultrinium and Perficio fluids. To take a guided tour on the subject, click on the presentation link below. For best results …

1. click on the full screen icon in the lower right corner of the slide frame,

2. click the “Allow” button to accept full screen mode, and

3. click on the play icon in the lower left corner to start the presentation.

 Between orange and lemon juice  

 

The presentation transcript follows …

01: What danger lies between orange juice and lemon juice? {Advance}

02: To answer this pressing question we have to understand what alkaline and acid mean. In water, chemists use the “pH” scale to delineate alkalinity and acidity. Technically pH is the negative logarithm of the hydrogen ion concentration, but you don’t have to understand logarithms or chemistry to understand alkalinity and acidity, because we experience most of the range of the alkaline-acid scale in our everyday lives. {Advance}

03: Let’s start with the alkaline portion of the scale. Anything with a pH greater than 7 is alkaline. Near the top of the list is liquid drain cleaner. If you get drain cleaner on your skin, wash it off immediately with copious water. While the word “acid” gets the rap for being dangerous, highly alkaline is just as bad as highly acidic. Moving down the scale, chlorine bleach is not nearly as irritating, but don’t leave bleach on your skin for too long … wash it off too. As we move down the pH scale the level of irritation becomes less and less. Soapy water left on your skin for a long time can be quite irritating too. In fact, our skin is acidic so all alkaline materials create some irritation over long enough time periods. {Advance}

04: Now consider acids. Human skin and black coffee share the same pH … about 5. We regularly drink tomato juice and orange juice at pH of 4 and 3 respectively. And we squeeze lemon juice into water or onto our fish, but for most people’s tastes, lemon juice is a bit too sour, or too acidic, to be drunk without some sugar added. In any case, these drinks don’t provide any problems to our bodies, because our stomach acid has a still lower pH. Let’s focus on that lemon juice for a moment longer … {Advance}

05: Did you know that over 6 million people die each year from lemon juice burns? … Just kidding … I was checking to see if you were engaged. The worst thing that can happen with lemon juice is a squirt to the eye. That can sting, but your eye will recover. {Advance}

06: Why does the word acid have such a bad rap? Is it the burning of skin from the acid in a lead-acid battery? Is it 30-weight-percent laboratory acid like hydrochloric acid with a pH of negative-one? {Advance}

07: Or is it alien blood, so acidic that it eats rapidly through metal floors on Hollywood movie sets? {Advance}

08: It might come as a surprise to some, but that is not really possible. A close examination of the Hollywood special effect demonstrates that the “metal” is really Styrofoam® and the acid is really an organic solvent. You can try this at home with some Styrofoam and gasoline. Drip the gasoline from well above the Styrofoam to get the cool splatter effect. {Advance}

09: I am not entirely sure why acid is a scary word, but let’s examine the space between orange juice and lemon juice. {Advance}

10: Two fluids that occupy that space are Coca-Cola® Classic – the Real Thing®, and another real thing, Novinium brand Ultrinium™ and Perficio™ fluids. Make sure you don’t spill either on a metal floor … they eat right through it like alien blood! {Advance}

11: So what danger does fall between orange juice and lemon juice? Advance the view again to summarize the answer … {Advance} Maintain healthy skepticism of what you learn from Hollywood and from fear mongers.

 

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Crazy Competitor Claims

by Thermo 19. March 2013 16:50

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.

by Thermo 23. January 2013 17:05

Neutral Corrosion & Novinium Warranty

Dear Informed Frog-

I have been asked to pursue something in writing concerning the 50% neutral corrosion and Novinium’s warranty. I respectfully request to have this from Novinium by quitting time this Friday, January 25, 2013. Thank you in advance for your cooperation in this matter and feel free to call me with questions or problems.

Signed,

Corrosion Concern in Colorado

Dear Concerned-

Short Answer

Go to …

http://www.novinium.com/Warranty.aspx

… and search for the word “corrosion” … you won’t find it! The warranty is purposely silent on neutral corrosion.

Less Short Answer

To understand why the short answer is so short, it is really useful to understand the purpose of the neutral and the consequences of various levels of neutral corrosion on the performance and reliability of the cable. To this end, view the recording of the September 2012 Webinar or read the webinar’s companion paper, “Neutral Corrosion – Significance, Causes & Mitigation”  prepared and presented by some of the cable experts at the Insulated Conductors Committee of the IEEE that created IEEE 1617, the IEEE "Guide for the Detection, Mitigation, and Control of Concentric Neutral Corrosion in Medium Voltage Underground Cables."

Based upon IEEE 1617 and the aforementioned webinar many circuit owners have chosen 50% corrosion as their cutoff point for rejuvenation. But you get to make that determination yourself. You need only to communicate your wishes to the Novinium masters that proide your services. If you would like to discuss your choice with an expert … you can find them at Novinium. As you will learn in the webinar the 50% rule-of-thumb is a “glass half-full” proposition, because the rate of corrosion in direct buried cables declines over time. The pessimistic “glass half empty” perspective is not supported by observation.

Even if you have the occasional neutral corrosion in excess of 50%, don’t despair. The corrosion can be pinpointed and repaired, generally at a fraction of the cost of replacement. The webinar explains that option too.

Neutral on neutrals,

Thermo

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Operational Considerations | Warranty Reflections

by Thermo 22. January 2013 19:46

A Cable Too Long

Dear Felicitous Frog,

I am currently reviewing a URD circuit with a cable segment that is 6,200' per our one-line and GIS.  It is our regular #2 db [direct buried] cable.  I am considering the installation of pull-boxes to break up the many long segments prior to attempting injection. What is the practical limit to TDR [time-domain reflectometer] testing?

What is the practical injection limit?   I assume in the best case that there at least a construction splice every 2000 feet, but there may be more that have to be replaced. 

Curious about cable  

 

Dear Curious- 

For background on how TDRs work, check out my October 1, 2011 post, “Reflections on a TDR”. A TDR sends a radar-like pulse down a cable. Like radar, a portion of the pulse is reflected when it “hits” objects along the cable path. Objects are anything that has a modestly different impedance (resistance, capacitance, and/or inductance) from that of the cable. Splices, cable ends, and neutral corrosion are generally identifiable. These objects are often called impedance anomalies, because the impedance varies locally from that of the cable.

There are two phenomena that reduce the acuity of the TDR – attenuation and dispersion. In the image nearby I illustrate the practical effects of attenuation and dispersion. As a wave travels along a cable its amplitude decays because no cable is without loss. When a male bullfrog croaks into a pipe, the volume decreases with distance because the sound wave amplitude attenuates. The attenuation is due to the imperfections in the molecular collisions. A portion of the sound waves are converted to heat. The same thing happens in the cable as electrons bounce among the cloud of conductor d-orbitals.

The second effect is dispersion and it too is the result of imperfections. Instead of loosing energy, dispersion smears energy because the rate that the signal moves through the cable is not uniform through its cross section. Skin effects and twisted stranding act to disperse the wave. Copper tape neutrals have a particularly nasty dispersion.

Simply recognizing these two effects helps the skilled operator interpret the observed wave shapes. Longer cables and those with more splices or corrosion will have shorter and more dispersed reflections.

Tactics to Improve Acuity

Of course the operator can use the TDR from both ends of the cable. This tactic effectively doubles the TDR’s resolution.

The next choice in the operator’s toolbox is to increase the pulse width. At the expense of resolving smaller or closely spaced impedance anomalies, wider pulse widths are the brute-force way to overcome both attenuation and dispersion.

A third choice is to divide and conquer.  Each construction or repair splice that is excavated provides an opportunity to TDR the two subsegments of cable from the splice in each direction.

Every cable is different, but more than likely the TDR should be able to identify all of the splices on a 6,200-foot run of No.2 URD cable employing just one or two of the aforementioned tactics.

Injection Length Limits

At Novinium, we know no bounds. We have a variety of patented injection paradigms to address long cable lengths. The preferred method for such a cable is sustained pressure rejuvenation (SPR). With SPR subsegments of cable are injected from termination-to-splice and from splice-to-splice. As you suggest, the longest run would likely be 2000 feet, the typical length of a cable reel. We have a model that allows us to predict injection times with great precision. Assuming your No.2 cable has round strands and 175 mils of XLPE insulation, a 2000-foot run utilizing SPR would require about 46 hours of injection time. We have treated cable subsegments that are several miles long and we have additional tools available for the most challenging circumstances.

With SPR the cable subsegments are typically deenergized during the injection process. If having the circuit deenergized for several days is not palatable, Novinium has still more tools at its disposable including flow-though splice technology that supports SPR. Of course, your suggestion of creating shorter subsegments by installing intermediate pull-boxes is another choice that can reduce the injection time.

Flow through really long runs of cable using older approaches is problematic. The challenges and the solution for really long cables, like submarine cables, are included in U.S. Patent 7,976,747 and in the paper, “Advances in Chemical Rejuvenation of Submarine Cables” presented at the Jicable conference in Versailles France in June 2007. To review this paper click here.

In short, we have many tools to address every conceivable situation. Talk to our crack field engineering team to explore all the options, or write back to me with more details and constraints. Check out our senior field Engineer Norm Keitges splashing in Puget Sound. He must have thought for a moment that he was a frog, because we generally frown on humans swimming on the job.

Bending boundaries,

T. B. Frog

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Operational Considerations

by Thermo 18. December 2012 15:05

Merry Masters

Oh festive frog-

It was a pleasure corresponding with you this year, toward a better understanding of cable rejuvenation. I also appreciate all the material you provided regarding cable testing.

I wanted to take this opportunity to personally wish you and your adoptive family a Merry Christmas and a healthy and happy New Year.

Emily

Dear Emily-

Thank you for the kind sentiments. I am hopeful that your holiday season will be filled with great times with those who you love. I’ll take this opportunity to wish all of mankind and creature-kind a wondrous holiday season and a prosperous 2013.

A glance at our Novinium Christmas tree reveals elements that you would expect to see.  Presents donated by our masters going to foster children to brighten their holidays. Unblinking white lights symbolizing electrical reliability delivered with unrivaled craftsmanship. Candy canes to satiate the sweet tooth for all those Novinium masters who were good boys and girls. Dennis, no candy cane for you until you quit smoking – because we love you.

A closer examination, however, reveals ornaments fashioned out of power cables. The cables are of many constructions and from all over the world. An even closer examination reveals that the tree-top star is fashioned from the fanned-conductor-strands of a feeder cable. You might think that our star is kind of cheesy, but then being born in a manger was not a glamorous affair. I was born in a swamp! That makeshift star reminds us that it isn’t the brightness of our lights that makes us good – it is the warmth we harbor in our souls. At least to this frog, Christmas is a time to thank God for Her good will.

Green Christmas wishes,

Thermo B. Frog

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Potpourri

by Thermo 11. December 2012 14:49

Third Party

Dear Alert Amphibian-

Can you provide third party data demonstrating that cable injection will extend the life cycle of underground cables? My colleagues and I are preparing for a rate filing with the OEB and we are looking for some firepower, facts and figures to bolster our case for additional cable injection monies for 2014 and beyond.

Seeking help,

Organizing in Ontario

Dear Organized-

I can think of four “flavors” of third-party data.

Flavor 1

Flavor 1 includes data gathered by third parties at the behest of a firm engaged in rejuvenation. The third party is independent, and is generally working for the technology supplier. There is an ample supply of this type of data, spanning over two-and-a-half decades. As an example of this type of data, consider Figure 3 of the paper published by my colleagues at the IEEE International Symposium on Electrical Insulation in September 2004…

New Developments in Solid Dielectric Life Extension Technology 

Figure 3 shows the substantial improvement in AC break-down performance seven days after injection at Cable Technology Laboratories. There is an abundance similar Flavor 1 third-party data. A compilation of that data can be found in the bibliography presented at the NETA Powertest Electrical Conference on March 17, 2008.

History and Status of Silicone Injection Technology with Bibliography

This paper provides 50 references including flavors 1, 2, and 3 of third-party data.

Flavor 2

The second flavor of third-party data are results reported by end-users. There have been several North American utilities that have reported their post-rejuvenation reliability over multiyear periods. The IEEE’s Insulated Conductor’s Committee (ICC) Discussion Group C30 is compiling several of these case studies as part of its efforts to craft a Guide entitled, “Extending the Life of Power Cables in the Field.” One exemplary data set was published by Northeast Utilities at the spring 2008 ICC. I have attached an excerpt of the ICC meeting minutes below. Over a nine year period from 1999 to 2007, the failure rate of the post-rejuvenated cable was 0.7% and the failure rate of the non-rejuvenated cable was 12%. Novinium’s failure rate is about half of the failure rate enjoyed with this older technology – see flavor 3.

R.Vencus. Cable Injection Program CL-P 2008.pdf (8.13 kb)

Flavor 3

The third flavor of third-party data is the overall failure rate of rejuvenated cables. Circuit owners have an incentive to report their post-injection reliability issues as they get cash for doing so! Novinium transparently publishes these statistics at …

http://www.novinium.com/Lessons.aspx

Novinium’s post rejuvenation failure rate is less than that of new cable! Check out my March 23, 2012 post, “Better Than New” to learn more.

Flavor 4

The fourth flavor of third-party data would be a Coke vs. Pepsi, side-by-side “taste test” of different rejuvenation technologies funded by electrical circuit owners and conducted by a third-party laboratory. There is good news, there is bad news, and some new that falls between good and bad. The good news is such a test was arranged by NEETRAC (National Electric Energy Testing, Research & Applications Center) sponsoring firms including: AEP, BG&E, ConEd, Oncor, FPL, Exelon, Southern Company, PEPCO, Southwire, and Snohomish Public Utility District. The bad news is that only Coke showed up for the taste test! The other technology supplier participated in the experimental design, but withdrew just as the testing was to commence citing, “Business and commercial reasons.” I will leave it for your contemplation why the other guys would not want to participate in a side-by-side test. The test proceeded with Novinium only. The news that is not bad, but not ideal is that even though the test was completed about two years ago, NEETRAC has not yet published the results in anything other than draft form. An excerpt of the draft NEETRAC report provides the bottom line of the testing:

“ … the stress at which the rejuvenated cables fail is higher than for the non rejuvenated cables: 26 kV/mm and 16 kV/mm, respectively. These stresses are taken at the 50th percentile (median). Moreover, it would appear that the [Novinium] rejuvenated cables have a threshold for failure at 4.5 kV/mm whereas there is no threshold for the Non Rejuvenated cables."

The reported performance advantage was measured after about 18 months of accelerated aging – well beyond the originally planned twelve-month experimental plan. The electrical stress of a typical 175 mil insulated URD cable energized at about 8kV to ground is 1.8kV/mm. The treated failure threshold is 2.5-times typical operating voltages even after extended thermal and electrical accelerated aging.

Ready for any party,

Thermonuclear Frog

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