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

Flash Point Matters

Dear Ms. Yorker-

That’s a really interesting question and a great learning opportunity. I touched upon this subject in two previous posts in 2010 and 2011, but 2012 is a new year so let’s take a fresh and more comprehensive look.

Before we dive out of the frying pan and into the fire, I want to comment on the quip, “… unbreakable from a lineman’s viewpoint.” Linemen take great pride on being able to break anything, and as we shall see later, the fallibility of equipment, the inevitability of equipment failure (whether or not that failure is encouraged by rough handling of burley line-personnel), the certainty that fluid will one day be released into the confined volume of your pad-mounted transformer, are precisely why this issue is so important.

Let’s reproduce a table of closed cup flash points from the November 2, 2011 post, because the values are very important. The materials with a red background are defined as flammable liquids by OSHA 29 CFR 1910.1200(c) and DOT 49 CFR 173.115-120.

It’s also important to understand what a closed cup flash point represents. Referring to ASTM D93-10 (Standard Test Method for Flash Point by Pensky-Martens Closed Cup Tester), a sample of fluid is placed in a closed metal cup at a temperature well below its flash point. The fluid and the air/vapor space above the fluid are well mixed as the temperature of the cup and its contents are uniformly increased at a prescribed rate of 5 to 6°C (9 to 11°F) per minute. A small shutter is opened at each 1°C increment, and an ignition source is lowered quickly (0.5 seconds) into the vapor space of the test cup. The ignition source lingers in its lowered position for 1 second. It is then quickly raised and the shutter is closed. This process is repeated until the vapor-air mixture flashes. The ignition source might be a propane flame or a spark. The temperature of the ignition source has zero impact on the flash point. That’s right, it does not matter what the temperature of an arc is – it may be 35,000°F or 35 million. It’s the temperature of the fluid that determines whether an ignition occurs.

Here’s why that is the case. I think everybody is familiar with the “fire triangle,” I illustrate nearby. In order for a fire or explosion to occur, there must be three things: A source of ignition, fuel, and oxygen. Part of Ms. Yorker’s point is that in medium and high voltage environments, sources of ignition are common. Of course, oxygen is also ubiquitous and hence the only thing that is missing to create a fire or explosion is the fuel. But just having fuel is still not enough! As we discussed previously, a spill of fluid (fuel) is inevitable, despite Herculean engineering and procedural efforts to prevent that event. For now, let’s assume the spill does occur from a tank failure, a failure of one of the fittings, the tubing, or an injection elbow. What happens next?  Check out Frogograph 1 nearby. The fluid will flow to the lowest point of the transformer enclosure. There may be a puddle or perhaps just fluid-wetted soil.  In Frogograph 1, the temperature at the bottom of the transformer is lower than the flash point. The flash point is indicated by the red “FP” arrow. Because the temperature is well below the flash point, there will not be enough fluid evaporation to reach the lower explosive limit (LEL). I’m perfectly safe standing there drinking my coffee.

The situation changes in Frogograph 2 as the temperature just exceeds the flash point. Now in addition to the blue liquid layer, there are three other possible strata, labeled <LEL, Goldilocks, and >UEL. Let’s start from the bottom – the UEL is the upper explosive limit. All flammable fluids require a threshold amount of oxygen to burn. As a practical matter, this light green stratum is very, very shallow and since the likely sources of ignition are higher within the enclosure, its presence is largely irrelevant. Now let’s jump to the uppermost stratum left clear in the illustrations.  In this stratum there may be some molecules of evaporated fluid, but there simply is not enough to ignite in a self-propagating chain reaction. It’s the red stratum, the “Goldilocks” zone, where there is just enough (not too much and not too little) fuel (vaporized fluid) and just enough (not too much and not too little) oxygen to support combustion. Because the transformer enclosure is not well ventilated and because the flammable vapors are heavier than air, these strata form at the bottom as illustrated. When a fluid vaporizes, its volume increases about 1000-fold, so even a small spill has the potential to create a large Goldilocks stratum. The rate of fluid evaporation is related to the difference between the temperature at the bottom of the enclosure and the flash point. The higher the flash point, the lower the rate of evaporation will be. There are three things that mitigate an increase in depth of the Goldilocks zone. Gravity will draw the spilled fluid into the soil. Secondly, enclosures are not air-tight and hence restrained convection will remove some of the vapor. Thirdly, my favorite law of thermodynamics, the 2^nd law or entropy, helps disperse the spill. Both liquid and vapor diffuse through air and soil acting to reduce the concentration of the fluid vapors. The Goldilocks stratum is checked by these three phenomena. For a given spill, the depth of the Goldilocks stratum will be determined by the difference between the temperature at the bottom of the enclosure and the flash point.

In Frogograph 3 the temperature is well above the flash point and the Goldilocks stratum is much larger. In this illustration, we imagine that the neutral bleed wire to the elbow does not make an adequate electrical connection and discharges occur at that point. As the Goldilocks stratum enlarges it eventually reaches this discharge and the Goldilocks volume ignites. Because the transformer provides mechanical confinement an explosion occurs and the lid is blown open violently.  That is precisely what happened in the photograph nearby to an Ohio circuit owner. Fortunately, no tadpoles were playing nearby.

Now go back to the flash point table above. Does the temperature in your transformer enclosures ever exceed 55°F (13°C)? Unless you are on the North Slope of Alaska, the answer is probably yes. If Alaska Airlines asks if they can store one gallon of jet fuel A in each of your enclosures, would you say yes? The jet fuel would be safer than the low flash point injection fluids.

How many fires and explosions would be too many on your system? Some may be stammering, “But, … but, we have never had a fire or explosion with the flammable rejuvenation fluid we have used in the past.” Lucky you … others have! As a standards engineer you should demand that all suppliers provide a complete accounting of all fires and explosions its process and fluid have ever experienced. If a vendor is unwilling to comply with this most reasonable request, you can disqualify that supplier. Let me preemptively supply the Novinium list … boring as it may be.

A partial compilation of fires and explosions suffered by circuit owners utilizing flammable rejuvenation fluid can be found at …

http://www.novinium.com/pdf/papers/Rejuvenation_Hazards_Analysis.pdf

... in Addendum C of the Rejuvenation Hazards Analysis, beginning at section 2.3.3. Specific examples are illustrated at 2.3.3.1.3b, 2.3.3.1.3.1.2c, 2.3.3.2.1c, and 2.3.3.2.2c. There are many more.

Thankfully, most of us have never been in a head-on auto accident, but we take comfort in the PPE designed into our cars, namely the seat belts and air-bags. We pay more for these features on our cars, not because we have had a serious accident, but because we wish to avoid the terrible consequences of such an event should it occur. Even better than seat belts and air bags, imagine a system that eliminated the risk of collision altogether.

Such a system is available to circuit owners enjoying the capital efficiency of rejuvenation. My final illustration in this post is the “Hierarchy of Control” nearby. The upside-down pyramid illustrates that the most effective way to deal with safety risks is to eliminate them. At Novinium we embrace this hierarchy and you should too. Eliminate known risks, substitute safer materials and processes for those that are less safe. Apply concentrated engineering effort to prevent occurrences and mitigate the impact when unfortunate and inevitable incidents do occur. Implement, but depend the least on administrative, behavior-based, and PPE controls.

With flash points greater than 142°F for Novinium’s Perfico™ 011 fluid and Ultrinium ™ 732 fluids (both of which enjoy patented methods including U.S. patents 7,658,808, 7,700,871 and 8,101,034 together with their foreign equivalents), fires are extraordinarily unlikely. But we don’t stop there. With our improved unsustained pressure rejuvenation (iUPR) we eliminate the 60 to 90 day soak period employed by the two-decade-old approach altogether. That’s about a 60-fold reduction in the exposure to a leak in the first place. With our patented sustained pressure rejuvenation (SPR) process (U.S. patents 7,615,247 and 8,205,326 and foreign equivalents) and associated injection adaptors (U.S. patents 7,195,504, 7,538,274 and 7,683,260 and foreign equivalents), the possibility of a leak is entirely eliminated. There’s more – a lot more. To understand how technology has vastly improved the safety performance of rejuvenation technology, see …

So here is the bottom line in my longest ever post.  Flash points and the impact they have on safety are in the public domain.  What will you say on the witness stand in defense of your firm when somebody or some frog is hurt by using the least safe technology?  To help you on the stand, cut out the handy cheat-sheet below and check all that apply.

Better safe than sorry,

Thermonuclear Bull Frog

Dielectric IV

In Dielectric I, I provided the first part of a four-part answer to a query from Alabama – the summary question: To what extent does the introduction of injection equipment into energized devices impact the safe operation of medium voltage circuits? We learned that there are great differences in the extent of this risk depending upon the injection paradigm employed. In fact there are three injection paradigms and at Novinium we use only the safest processes. With Novinium’s patented SPR (sustained pressure rejuvenation) there is zero additional risk. With Novinium’s iUPR (improved unsustained pressure rejuvenation) process the risk is many times less than the legacy approach used by others. The legacy paradigm is called UPR (unsustained pressure rejuvenation). In Dielectric II, I provided data and analysis that showed why the feed end of an iUPR injection is simply not a safety issue. In Dielectric III, I examined the design issues associated with the vacuum tank utilized for iUPR and the features that make iUPR the second safest injection approach, just behind Novinium’s SPR method. Both SPR and iUPR are available only from Novinium and our partners, as these injection paradigms require the application of patented technologies.

Alabama, you asked the eight questions below. Direct answers are provides below. The answers for (1) through (5) are taken from the previous posts.

(1) What is the insulation rating of the fluid(s) that you use for injecting?

Answer:  Several inches of Ultrinium™ fluid are enough to prevent substantial leakage current. The minimum amount of fluid between an energized device and a potential ground plane is 36 inches. There is at least a two order of magnitude overdesign.

(2) What is the insulation rating of the hose(s) you use from your canisters to the injection point?

Answer: The AC breakdown strength of the tubing we use is greater than 80 kV.

(3) What is the insulation rating of the canisters themselves?

Answer: The AC breakdown strength of the Novinium’s iUPR feed tank and iUPR vacuum tank is greater than that of the tubing in question (2).

(4) What is the insulation rating for the combination elbow/canister?

Answer: The tubing has the lowest AC breakdown strength at about 80 kV.

(5) Do you have the test data for these pieces of equipment? Will you share the test data with the group?

Answer: Novinium is all about transparency. We will share the relevant test reports with the writing group. The most important data has been provided in the previous posts.

(6, 7 & 8) Have you looked at the electrical separation distance from your canisters to the cover or live bushing?  Have you looked at the electrical separation distance from your canisters to ground wires in the equipment? Have you looked at the electrical separation distances from your canister connected to one phase and to the other phases in a three phase installation?

Answer: Of course, all of Novinium’s iUPR equipment is designed to be placed in dead-front enclosures and live-front applications – enclosed and exposed. As you look at the photographs of the iUPR equipment you will notice that they are made up of mostly dielectric materials. There are a few conductive brass fittings, but no conductor length is greater than an inch or two. With that design feature the components can be set into any high voltage environment without having a material impact on safe separation distances. Furthermore the equipment is typically deployed for only 12 to 48 hours.

Summary

Novinium’s SPR method completely eliminates the risks we have been discussing in these four posts. Novinium’s iUPR is a substantial improvement over the older UPR method. The elimination of the soak period reduces the exposure of potentially energized equipment over sixty-fold. On the feed side, iUPR equipment is inherently unable to become energized beyond a nominal static charge. On the vacuum side, iUPR equipment is designed to contain within its bowels at least 80 kV. Even with these inherent advantages and engineered safety factors Novinium assumes that the equipment is “potentially energized” and we handle the iUPR injection equipment with hot sticks. With Novinium’s iUPR process we have observed exactly zero occasions where the equipment is energized. Many of the Novinium masters of reliability have over a decade of field experience, some have over two, and have been involved in operations with the legacy UPR process. Those masters have witnessed events where equipment was actually energized. This safety issue with UPR is explicitly acknowledged by the sole purveyors of the UPR process in their U.S. Patent 7,704,087 dated April 27, 2010. Read the patent yourself if you doubt this frog, or check out the excerpt in my April 15, 2011 post, “Soaking II: Safety First.”

What remains confusing to me is why anyone would accept the risks inherent in the UPR process. I wouldn’t want to be the defendant explaining why I chose the least safe approach. A comprehensive analysis of the safety differences between the various injection paradigms and fluid choices are presented in “A Comparison of Rejuvenation Hazards.” Click here for the straight scoop.

Better safe than sorry,

Thermonuclear Bull Frog

Dielectric III

In Dielectric I, I provided the first part of a four-part answer to eight questions from Alabama. The eight questions can be summarized thusly: To what extent does the introduction of injection equipment into energized devices impact the safe operation of medium voltage circuits? We learned in the first installment that there are great differences in the extent of this risk depending upon the injection paradigm employed. There are three injection paradigms and at Novinium we use only the safest processes. With Novinium’s patented SPR (sustained pressure rejuvenation) there is zero risk associated with the interaction of energized circuits and injection equipment. With Novinium’s iUPR (improved unsustained pressure rejuvenation) process, the risk is many times less than the legacy approach employed by others. The legacy paradigm is called UPR (unsustained pressure rejuvenation). In my second post, Dielectric II, I provided data that demonstrated why the feed end of an iUPR injection is not a safety issue – unfortunately the same conclusion is not true for the legacy UPR process. The purveyors of UPR acknowledge safety shortcomings of UPR in their U.S. Patent 7,704,087. I provide a relevant excerpt in my April 15, 2011 post, “Soaking II: Safety First.”

In the illustration nearby I am propped up against iUPR vacuum equipment. When the iUPR injection method is utilized, fluid flows unidirectionally from the iUPR feed tank through the cable and into the iUPR vacuum tank. While the dielectric properties of the fluid flowing into the cable are well known and stable, there is no way to be certain what will come out the other end. From a design perspective the Novinium engineering masters must assume that conductive water will flow from the outlet termination and into the iUPR vacuum tank.  The same 80 kV rated tubing is used on the vacuum side as was described in the previous post. The rating of the vacuum tank itself is higher still.

Of course, 80 kV is more than enough over-design for medium voltage applications, but there are other factors which provide the iUPR process a “belt and suspenders” robustness. Consider these three …

(1) It is very unusual for water to be in the strands of URD cables with 19 or fewer strands. I know that many believe the opposite is true, but the masters at Novinium have been injecting cables for over 25 years. If liquid water in URD cable strands were common we would see it – we don’t!  The occurrence is less than 1%. Where water is found in the strands is on pole terminated cables where the terminator design has a leak so that every time there is precipitation, water finds its way into the strand interstices. Don’t purchase pressed lugs – buy only solid lugs. If you want to know why there generally is not water in cable conductors, read “Molecular Thermodynamics of Water in Direct-buried Power Cables” from the Nov/Dec issue of IEEE Electrical Insulation Magazine. Click here to check it out.

(2) In the rare case where there is water, the time in which water will be in the tube is very limited. While cables are designed for continuous operation at operating voltage, the iUPR vacuum equipment is exposed for zero to perhaps sixty minutes. Any short duration exposure is eliminated when dielectric fluid flushes the last of any water from the strands and tubing.

(3) 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 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 length. As the pressure decreases CO₂ is liberated. The viscosity of 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.

iUPR has simply never had issues arise in thousands and thousands of field applications. iUPR is not as safe as SPR, but it comes in second place.

In my final post, Dielectric IV, I will address the equipment separation issues Alabama raised in his questions, 6 through 8.

Never in a vacuum,

Thermo B. Frog

Dielectric II

In Dielectric I, I provided the first part of a four-part answer to a query from Alabama – the summary question: To what extent does the introduction of injection equipment into energized devices impact the safe operation of medium voltage circuits? We learned that there are great differences in the extent of this risk depending upon the injection paradigm employed. In fact there are three injection paradigms and at Novinium we use only the safest processes. With Novinium’s patented SPR (sustained pressure rejuvenation) there is zero additional risk. With Novinium’s iUPR (improved unsustained pressure rejuvenation) process the risk is many times less than the legacy approach used by others. The legacy paradigm is called UPR (unsustained pressure rejuvenation). In this post I provide data to show why the feed end of an iUPR injection is not a safety issue – unfortunately the same conclusion is not true for the legacy UPR process.

In the illustration nearby I am standing next to iUPR injection equipment. From left to right are …

A CO₂ cylinder enclosed in a PVC bag provides energy to urge fluid into the cable strands.  A polyethylene CO₂ supply tube provides about 20 psig of pressure to the predominantly plastic feed tank. At least three feet of polyethylene fluid supply tube with a wall thickness of 100 mils delivers fluid to an injection adapter and a mated injection elbow. In another case not illustrated, the fluid might be supplied to a live-front injection adapter. Whether dead-front or live-front, the fluid comes in direct contact with an energized conductor. The fluid is a dielectric, and with Novinium’s improved unsustained pressure rejuvenation process, the flow is one way – toward the termination. This one-way flow provides assurance that there is no fluid contamination from backward flow as suffered by legacy approaches. At Cable Technology Labs (CTL) the leakage current in a column of Ultrinium™ 732/40 fluid was measured between two electrodes at 15, 25, and 35 kV. The leakage current was steady at about 0.03 mA, 0.04 mA, and 0.05 mA for 15, 25, and 35 kV respectively from 14 feet of electrode separation down to less than 1 foot.

With the Novinium iUPR process there are no ground electrodes ever in direct contact with the fluid. The fluid flows though several feet of PE tubing with a wall thickness of 100 mils. The AC breakdown strength of the PE is at least 800 volts/mil and hence the AC breakdown strength of the tubing is greater than 80 kV. The fluid flows from a polypropylene/acetal tank with even thicker walls than the tubing. The closest ground plane is typically the concrete or earth on which the feed tank rests. Novinium has deployed these iUPR systems thousands and thousands of times and there have been zero issues. We wrap the CO₂ cylinder in a PVC bag to prevent accidental contact with exposed secondary voltages.

In my third post in the series, Dielectric III, I will discuss the design issues of the vacuum tank designed for iUPR and the features that make iUPR the second safest injection approach. Finally, in Dielectric IV, I will address the equipment separation issues Alabama raises in his questions, 6 through 8.

Dielectrically delighted,

T. B. Frog

Dielectric I

Dear Wisest Webbed one,

I am working on my comments/concerns for the Safety Section for the C30 Draft Guide [Editors note: C30 is a group within the IEEE/PES/ICC working towards the writing of a “Draft Guide for Rehabilitation and Rejuvenation of Extruded Dielectric Cable Rated 2.5 kV through 46 kV.” While that Draft is being crafted, interested readers may wish to review a Novinium published early version undertaken at the behest of the group’s chair, which is available at www.novinium.com/Standards.aspx.], and have a few questions. Just because the equipment is all or mostly plastic materials, these questions still need to be explored and discussed.

1. What is the insulation rating of the fluid(s) that you use for injecting?
2. What is the insulation rating of the hose(s) you use from your canisters to the injection point?
3. What is the insulation rating of the canisters themselves?
4. What is the insulation rating for the combination elbow/canister?
5. Do you have the test data for these pieces of equipment? Will you share the test data with the group?
6. Have you looked at the electrical separation distance from your canisters to the cover or live bushing?
7. Have you looked at the electrical separation distance from your canisters to ground wires in the equipment?
8. Have you looked at the electrical separation distances from your canister connected to one phase and to the other phases in a three phase installation?

Your froguidance would be appreciated.

Alabama detailed draft

Dear Alabama-

I don’t know about you, but the fact that the first three letters in dielectric spell “die” makes me want to take extra measure to assure the safety of all who use dielectric enhancement technology. The heart of your eight questions can be summarized thusly: To what extent does the introduction of injection equipment into energized devices impact the safe operation of medium voltage circuits? Before I answer that question generally and some of your more specific questions, it is important to recognize that there are three distinct methods of dielectric enhancement fluid injection and two conductor realms in which those methods are deployed. Ordered from oldest to most advanced, the three methods are:

    UPR ♦ Unsustained Pressure Rejuvenation,

    iUPR ♦ improved Unsustained Pressure Rejuvenation, and

    SPR ♦ Sustained Pressure Rejuvenation.

To learn more about the details of these rejuvenation methods, check out my June 18, 2010 post titled “How to Inject.” Novinium is synonymous with safety, so we use the two most advanced processes almost exclusively. In the very unusual cases where Novinium leaves injection devices attached to energized devices for more than a couple of days, equipment designed specifically for that case is deployed. Because it is a rare case, I refer interested readers to my April 15, 2001 post, “Soaking II: Safety First” for more details.

In this series of posts, I focus on the cases most important to circuit owners. In the table nearby the implementation of the three injection methods are compared for the two conductor cases, namely small conductor and large conductor. Small conductors include stranded conductors, generally with 19 or fewer strands. Note that for large conductors, cables are injected de-energized whichever injection method is utilized, and hence your questions are moot for these large conductors. Further, SPR is applied over 99% of the time to deenergized cables, and hence the questions are again largely moot. The only firm in the world that can deliver iUPR and SPR is Novinium, because we own the intellectual property on the methods and chemistry that make those processes possible. For most injection work we undertake, we operate in the green … my favorite color.

When we do inject into energized devices we mitigate the risks about which you are inquiring by limiting the period that injection equipment is connected to energized components. In the red portion of the table, older technology requires extensive soak periods spanning several months. At first glance you might assume that reducing the period of time by sixty-fold would reduce the exposure to the risk by sixty-fold, but you would be underestimating the impact. In the iUPR process, fluid flows in only one direction. A feed bottle with a positive pressure, typically about 20 psig, is attached to one cable end and a vacuum bottle with a negative pressure of around -10 psig is attached to the other cable end. Fluid flows from high to low pressure. Both the feed tank and the vacuum tank are removed concurrently. Thus on the feed side, fluid with a high dielectric strength flows through tubing made of a high dielectric polymer and there is a negligible probability of substantive current flow. I’ll provide some data in my second post, Dielectric II.  With iUPR the only substantive design issue is on the vacuum or outlet side, there is no way to be certain what will come out of the outlet, so we have to assume that it will be water. In practice, water seldom comes out of 7-strand or 19-strand cables (To learn why, click here.), but from a design perspective this is the worst-case assumption.

UPR has the same worst-case on the outlet end, but it also suffers from a more insidious issue on the inlet end. I examined this issue in some detail in my April 15, 2011 post, “Soaking II: Safety First.” You should read that post, but in summary, UPR suffers a risk that conductive contaminants will render the feed fluid conductive. The worst-case assumption on the inlet side is about the same as the on the vacuum side, but the feed is connected for 60 days or more. This risk is recognized by the practitioners of UPR, because they explain the risk and a potential solution to mitigate the risk in U.S. Patent 7,704,087 of April 27, 2010. Amazingly after exposing the risk those practitioners have not implemented their mitigation strategy. I usually speak only of technical matters, but you don’t have to have a law degree to recognize that if you know about a safety problem, but do nothing to mitigate the issue – your liability undoubtedly increases. Risk managers should take this knowledge into account as they make their choice between the various injection processes. If your firm believes in safety as the most important criteria, don’t utilize UPR.

In my next post (Dielectric II), I will provide some data to show why the feed end of an iUPR injection is not a safety issue. In my third post in the series (Dielectric III), I will discuss the design issues of the vacuum tank designed for iUPR and the features that make iUPR the second safest injection approach. Finally, in Dielectric IV, I will address the equipment separation issues you raise in your questions, 6 through 8. For a thorough description of all of the rejuvenation dimensions of safety check out the 89-page treatise, “A Comparison of Rejuvenation Hazards & Compatibility.”

Practicing safe rejuvenation,

T. B. Frog

LIPA

Dear Felicitous Frog-

I have read a paper from the conference record of the 2008 IEEE International Symposium on Electrical Insulation (ISEI) by some folks at Powertech Labs from my home province of British Columbia. The paper was titled: “Condition Assessment of 15 kV Rejuvenated Underground XLPE Cables.” The cables in question are operated with AC, but the testing method is with DC.  Does a DC test have validity on an AC cable? The paper shows results of before-and-after diagnostic testing on two treatment methods, referred to as “method A” and “method B.” Are these results representative of Novinium’s post injection experience?

Currently,

AC in BC

Dear AC-BC:

Other frog fans may wish to review the full text of the paper to which you refer. The paper is available for a small charge from the IEEEXplore^® digital library; click here to view the abstract and full citation. The test method utilized in the paper is the LIpATEST™ technique, proprietary to PowerTech Labs. PowerTech is primarily owned by BC Hydro. The LIPA technique measures the DC leakage current through the cable insulation as a function of applied DC voltage. The 15 kV-class cables described in the paper are subjected to a negative voltage, increased in 4 kV steps of 1-minute duration, to a maximum of 16 kV. The leakage current is recorded at each step. The purveyors purport that the magnitude of the leakage current and its rate of change with applied voltage provide an indication of the quality of the cable insulation.

You asked two questions: Is the test valid and are the results representative? I provide answers to both in four parts, entitled: DC Testing, LIPA Validation, Rejuvenation Methods Tested, and Representative or Not?

DC Testing

The 2001 version of IEEE 400™, “Guide for Field Testing and Evaluation of the Insulation of Shielded Power Cable Systems,” provides some guidance and is available from ANSI. Click here to view the abstract and complete citation. Paragraph 4.2 states in part …

“Whenever dc testing is performed, full consideration should be given to the fact that steady-state direct voltage creates within the insulation systems an electrical field determined by the geometry and conductance of the insulation, whereas under service conditions, alternating voltage creates an electric field determined chiefly by the geometry and dielectric constant (or capacitance) of the insulation. Under ideal, homogeneously uniform insulation conditions, the mathematical formulas governing the steady-state stress distribution within the cable insulation are of the same form for dc and for ac, resulting in comparable relative values; however, should the cable insulation contain defects in which either the conductivity or the dielectric constant assume values significantly different from those in the bulk of the insulation [Editor: That would be all aged cable!], the electric stress distribution obtained with direct voltage will no longer correspond to that obtained with alternating voltage. … Furthermore, the failure mechanisms triggered by insulation defects vary from one type of defect to another. These failure mechanisms respond differently to the type of test voltage utilized. For instance, if the defect is a void where the mechanism of failure under service ac conditions is most likely to be triggered by partial discharge, application of direct voltage would not produce the high partial discharge repetition rate that exists with alternating voltage. Under these conditions, dc testing would not be useful. However, if the defect triggers failure by a thermal mechanism, dc testing may prove to be effective. For example, dc can detect the presence of contaminants along a creepage interface.

In the case of joints and accessories, their dielectric properties may differ from that of the cable with regard to conductivity. This may result in a dc stress distribution at the interfaces between the cable and the accessory that is very different from the stress under ac voltage. A careful examination of the system is necessary prior to a dc test in order to avoid difficulties.

Testing of cables that have been service aged in a wet environment (specifically, XLPE) with dc at the currently recommended dc voltage levels (see IEEE P400.1) may cause the cables to fail after they are returned to service (see Fisher, et al. [B23], and Steennis, et al. [B48]). The failures would not have occurred at that point in time if the cables had remained in service and not been tested with dc (see Eager, et al. [B21], and Srinivas, et al. [B47]). Furthermore, from the work of Bach, et al. [B7], we know that even massive insulation defects in extruded dielectric insulation cannot be detected with dc at the recommended voltage levels.”

In short, …

1.    DC testing does not measure the same defects to which the subject cable is exposed in its AC environment.

2.    There is little or no relationship between DC test results and likely AC performance.

3.    DC testing damages the aged cable it seeks to diagnose.

LIPA Validation

If the purveyors of the LIPA test wish to validate their test they simply need to run an experiment with a suitable control. To wit, divide a population of, say 100, homogenously aged cables into a control group of 50 and a test group of 50. Monitor the performance of the control group for future failure history. Submit the 50 cables in the test group to LIPA, and then monitor that group for future failure history. If the purveyor’s claims are accurate, there will not be a significantly higher failure rate in the test group compared to the control group and the failure rate in the subgroup of the test group that tested “bad” should be significantly higher than those of the test subgroup that did not test bad. Since PowerTech is a subsidiary of a utility with a sizable population of appropriately aged cables, it should be a simple matter to arrange such a test. This frog is unaware of any such test. Without the simple application of the scientific method the claims of efficacy cannot be confirmed by this, or any other frog.

Rejuvenation Methods Tested

Novinium can and does utilize both method A and method B. Method A is properly called unsustained pressure rejuvenation or UPR. Novinium has made improvements to the UPR method. The improved UPR method is called iUPR. Method B is sustained pressure rejuvenation or SPR. SPR outperforms UPR and iUPR by any measure of post-injection reliability.

Representative or Not?

Not – for two reasons. First, as mentioned above, the LIPA test should not be used to judge AC reliability. Second, even if LIPA were a valid test, 13 samples for UPR and 4 samples of SPR are not statistically significant.

Novinium is the only rejuvenation vendor in the world that performed a full third-party, side-by-side controlled experiment of rejuvenation technology. The work was executed by NEETRAC and the results are extraordinary. As soon as those results become public you can read about them here. In the mean time, actual post-injection performance of better than 99.6% on millions of feet of cable can be viewed at …

www.novinium.com/Lessons.aspx

Always skeptical of claims without data,

T. B. Frog

The Color of Capital

Dear Gregarious Green One,

My firm uses Ultrinium™ and Sustained Pressure Rejuvenation to treat cables after they fail. The ability to capitalize single section injection with Novinium technology means we can earn a regulated rate of return on the capital thus expended. I read your four-part blog, “The Color on Money” and was wondering if you could do a similar analysis to help us quantify the benefit of our approach.

Considering Capital in Colorado

Dear CCC-

I am pleased that you appreciated my “Color of Money” posts. Click on I, II, III, and IV to review that work. Many of the concepts in the “Color of Money” apply to the “Color of Capital.” In fact, Parts II and III are prerequisites if you need a primer on depreciation and the time value of money respectively.

The ability to capitalize single sections of injected cable is available only from Novinium. In FERCs (Federal Energy Regulatory Commission) Letter order dated January 18, 2000, John Delaware, the Chief Accountant, wrote to the petitioner, Georgia Power:

“You indicate that CableCURE is used to rehabilitate entire segments of your underground distribution system (e.g. entire residential subdivisions as opposed to individual runs of cable between two terminal points).”

The only way you can capitalize CableCURE is if the entire subdivision is rejuvenated. The letter order is attached to this post for the interested reader. Novinium’s technology has no such limitation. The Letter Order promulgated by FERC’s Chief Accountant on September 4, 2008 and associated submittal information removes that limitation and can be accessed by clicking here. All of the above discussion is also true for RUS-funded circuit owners. Click here is view the RUS order of April 3, 2009.

That takes care of the regulators; now the analysis. We will compare two cases. All of the inputs are shown on the worksheet nearby. Parenthetical references to the worksheet cell designations appear in the following text.

Case 1

The cable fails, is repaired and put back in service. In our model the user can indicate how many faults are tolerated before the cable is replaced, together with an estimate of the time between faults. For this example, we assume the cable will fault twice over a two year period before it is replaced. The capital cost to replace is a modest $33.00/ft (Cell B7) and the O&M cost of a fault is $13.72/ft (Cell D13) in today’s dollars. That’s $4,500 (Cell B11 + Cell B12) divided by as assumed segment length of 328 ft (Cell B13).

Case 2

The cable fails, is repaired and injected in a single integrated operation. In our model the bundled unit capital is $20.06/ft (Cell D23). The model user can change any of the costs inputs and an assumption of the post-treatment reliability. For this example, the post-treatment failure rate is assumed to be 2% (Cell B26), which is about twice Novinium’s actual post-failure experience of about 1%.  To put this 1% failure rate in perspective consider that it is three-times higher than Novinium’s non-post-failure experience of about 0.34%. This higher-than-typical post-treatment failure rate is inherent in post-failure treatment. The post-injection fault is assumed to occur two years (Cell B27) after injection. Again the model user can adjust any of these assumptions.

Other Assumptions

Warranty remittances of $10/ft (Cell B23) are negative capital expenditures, that is, the remittances are subtracted from the subsequent replacement capital. Upon post-injection failure, the book value is written off, terminating the ratemaking-allowed return and providing a lump sum tax benefit of the book value. Cash flows are calculated for two rehabilitation cycles, up to 100 years. This approach allows residual values to be properly ignored as de minimis. Finally, replacement is assumed to have a zero-percent failure rate. At least one major investor owned utility has reported that new installations suffer a 0.6% “infant mortality” failure rate, and hence this assumption results in a slight understatement of the incremental value of Novinium^® post-failure rejuvenation.

Bottom Line

The cumulative net present values (NPVs) for the two cases are plotted nearby. Since the revenue or sale of electricity is the same in all cases, those revenues are ignored and only capital and O&M costs are depicted. This cost-only analysis is why all of the NPV values are negative. Nonetheless, the higher the cumulative NPV value is on the graph, the more advantageous to the circuit owner.

The blue line is for Case 1, and in the short run it is the superior choice. The problem is that once a cable begins to fail, it will re-fail. Sooner or later the ratepayers will be very upset with deteriorating reliability. Capital inefficient replacement is executed after the second fault (Cell B14) and the NPV plummets.

The orange line is for Case 2, and it represents an investment in reliability. The initial cost is about twice as great, but because the investment is capital, the circuit owner begins to earn a regulated rate of return. In the end, the incremental NPV advantage of Novinium post-failure rejuvenation is $18.42/ft. If your replacement cost is higher, say $44/ft, the difference becomes $21.15/ft. If in Case 1, the cable is allowed to fault a total of three times, the difference rises to $24.56/ft. Even if the cable is replaced after a single fault, the best alternative to rejuvenation, rejuvenation still enjoys an $11.45/ft advantage.

If you would like to run this model on your specific circumstances and execute “what if” scenarios, contact us at novinium.com/Contac.aspx.

Always conserving capital,

T. B. Frog

70-20120322_FERC_Letter_of_Approval.pdf (78.87 kb)

The Color of Money – Part I

Dear Gregarious Green One,

My firm purchases rejuvenation services from both Novinium and UTILX. While we have a preference for the mastery displayed by your team and your inherently safer process and fluids, it is difficult for us to settle on Novinium as our sole vendor, because the UTILX price is lower. Can you help me understand your value?

Capital Concern

Dear Cap-

I’ll bet that you thought my FrogBlog tagline, ”It’s easy to be green™” focuses upon the environmental benefits of using Earth-friendly cable rejuvenation technology. Others might believe that the tag line is a play on the lyrics to that other famous frog’s song, “It’s Not Easy Being Green.” This frog is a master of the triple entendre. It’s easy to be green, while you are saving some green, and … I am not above poking fun at Kermit! Notice in the image nearby how nicely my complexion matches the color of money! That’s money that you earn when you employ superior technology.

We can provide a lower price by lowering the quality of the products and services we deliver to more closely match those of the two-decade-old approach, but we will not compromise on safety. For example, we will not use flammable fluids. But hey, there is no need to compromise safety or performance. The value of the longer post-injection reliable life and the longer warranty periods enjoyed by the patented Novinium processes and fluids can be calculated. Let’s consider two general cases.

In the first case, compare the 20-year life expectancy, warranted by the other guys, versus the 25 years enjoyed by the improved unsustained pressure rejuvenation (iUPR) process together with Ultrinium™ 732 fluid. At first glance 25-year life extension suggests a 25% increase in value, but there are the matters of the time value of money, regulated rates of return on capital, and distortions caused by the tax code. In the graph nearby I show the difference in net present value (NPV) between the two choices as a function of the post-injection reliable life. The actual value waxes and wanes depending upon the life of the cable, but for the most common case, where the life meets the expectations, iUPR enjoys more than a 10% value advantage. For other cases the value may be higher or lower, but it is generally positive.

In the second case, compare the 20-year life expectancy, warranted by the other guys, versus the 40 years guaranteed by the sustained pressure rejuvenation (SPR) process together with Ultrinium™ 732 fluid. Doubling the life extension does not double the value, because of the aforementioned time value of money, regulated rates of return, and tax code considerations. In the second graph I show the difference in net present value (NPV) between the two choices as a function of the post-injection reliable life. The actual value varies depending upon the life of the cable, but for the most common case, where the life meets the expectations, SPR has about a 16% value advantage. For other cases the value may be higher or lower, but it is always positive. For cases where the post-injection life is greater than 3 years, but the cable fails within the warranty period, the SPR/Ultrinium 732 fluid combination provides up to a 32% value advantage.

In subsequent posts, this frog will again crack open her Frogonomics 101 textbook and explain each of the factors that influence this dispassionate economic analysis. Friends of Frog (FoF) may request a copy of the MS Excel worksheet so that they can adjust the parameters of the model to calculate their unique incremental value of using state-of-the-art technology.

Always in the green,

Thermo B. 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