On-line Diagnostic Testing

Dear Ms. Conducting-

Thank you for your comment of May 13, 2011 to Middle East Query – Diagnostic Testing Timing.  Click here to see the original post and comment.  In short, Ms. Conducting wanted to dive deeper into the data. Below I have reproduced slide number 281 from the CDFI (Cable Diagnostic Focused Initiative) Regional meeting presented by NEETRAC (The National Electric Energy Testing Research & Application Center at Georgia Tech’s College of Engineering) and hosted by American Electric Power (AEP).  The meeting was held on October 13-14, 2009 in Columbus, Ohio, U.S.A. The entirety of the presentation slides are available by clicking here. The figure below (from slide 278) shows the failure results tracked for over three years on 114 feeder cable miles tested using online PD on cables that included EPR, XLPE, and PILC cables. After the testing was completed, the cables and attached accessories were allowed to fail – that is, no rehabilitation actions were taken.  There were about 85 accessory failures; there were about 90 cable failures.

 The online PD testing indicated the need for action (i.e. imminent failure) on 45 accessories.  Of the identified 45, 14, or 31%, actually failed.  The false positives were 69%. The results on the cable were marginally better. Of the 52 cables, which were diagnosed as “bad,” 23 actually failed or about 44%.  The false positives were 56%.  For both accessories and cables the number of faults that occurred on plant, that had been deemed “good” by the testing firm, far outnumbered those identified as “bad.”  There were about 71 and 67 false negative failures for accessories and cable respectively.

Not only did the observations show that the testing was unable to provide reasonable discrimination between bad and good, the raw number of failures that occurred in the presumably “good” sub-population was about 3 to 5 times higher. Because the researchers did not provide population statistics beyond the total mileage of cable installed, it is not possible to determine with precision the relative false negative performance. However, I can make some frogstimates. If the average three-phase feeder run length were 1760 feet (typical for North America) and there were 2.2 components per cable segment (also typical), there would have been approximately 343 cable segments (or about 114 three-phase cables, termination to termination) and about 750 accessories.  The relative failure rate over the three-year period would have been 11% (i.e. 85/750) for accessories and 26% (i.e. 90/343) for cables. My frogstimate of the false negatives are 9.5% (i.e. (85-14)/750) and 19.5% (i.e. (90-23)/343) for accessories and cables respectively.

Amazingly, these profoundly dismal results are spun by testing proponents as proof that a testing program is a fruitful endeavor. It’s no wonder to me why humans get sucked into tulip and real-estate bubbles and Ponzi schemes – no frog has ever been so duped.  There have been a few would-be-princesses that have been duped by a frog, but never the other way around.  Alas, wishing that a frog is a prince does not make him so. Wishing that a diagnostic provides useful information does not make it so.

There are two immutable reasons and their “anti-synergy” that explain why the current generation of diagnostics cannot work. These two reasons are:

1.   The economics of aged circuit rehabilitation, and

2.   The second law of thermodynamics.

Further, without some technological breakthrough that reduces the cost of applying diagnostics by an order of magnitude, it is unlikely these immutable and anti-synergetic forces will ever be reconciled. To inoculate yourself from these ill-conceived schemes, read and understand the DEIS (Dielectric and Electrical Insulation Society) feature article, “Diagnostic Testing of Stochastic Cables” published in the March/April 2009 pages of IEEE’s Electrical Insulation Magazine.  Click here to learn.

Data and Frogs don’t lie (unless you’re a fly),

T. B. Frog

Middle East Query – Novinium Splices & Terminations

Dweller of the Desert asked 22 questions in his post …

Middle East Query – 22 Questions.

In this final installment, I address questions 18 through 22 as they are all related to the splices and terminations utilized for sustained pressure rejuvenation or SPR.  Here are the questions my dry friend posed …

18. If a cable were to fail after injection, can the customer use ordinary splices? Or should he use the “Novinium” specified splice? Can we use the traditional splices and terminations if a fault took place after treatment? In other words, do we have to use your splices and terminations on any treated cable all the time or that is only during treatments?

The probability of post-injection failure is quite low, but no rehabilitation approach is perfect.  In the event that a post-injection failure does occur there are Novinium Rejuvenation Instructions (NRI-99) for “Cutting a treated cable.”  Click here to see NRI-99. Step 9 of NRI-99 encourages the circuit owner to send a failure sample to Novinium so that we may learn from the experience. There are another set of instructions, NRI-93, which describe the best way to handle the failure sample.  Click here to see the NRI-93 “Failure Sample Handling” instructions.

Once the failure is dispatched, it is time to repair the cable. Step 10 in NRI-99 encourages the use of Novinium^® brand injection adaptors (IAs) to seal any remaining fluid in the cable. These IAs are inexpensive and provide a fluid-tight seal so that rejuvenation fluid does not come in contact with the new splice body and so that water can never enter the cable strands. At Novinium, we use only “ordinary” splices.  In fact, Novinium injection technology is compatible with most splices. Click here to view two lists of Novinium Certified components. On that web page Table 1 provides a comprehensive list of dead-front terminations and Table 2 does the same for splices. If your splice of choice is not found in the table let me know and we can initiate the certification process.

19. Do the existing cable terminations need to be replaced? Will this introduce new splices?

Rehabilitation of a circuit is best accomplished if all the accessories are rehabilitated too.  It makes little sense to extend the life of a cable by decades and leave 30-year-old terminations or splices in place.  A chain is only as strong as its weakest link. For this reason, all terminations and splices are normally replaced to install Novinium injection adaptors and to ensure that proper craft work accompanies the rejuvenation of the cable.  Twenty-plus-year-old-terminations and splices cannot be expected to last several more decades.   If there is no slack in the cable, each cable lug is split off, so that no cable length is lost.

20. Are your splices and terminations available in the market or it is unique to Novinium?

Novinium only uses commercially available splices and terminations.  However, we qualify each commercially available termination and splice before use to insure that it will allow Novinium to also install an injection adaptor and still remain inside of the conductive insert of the accessory.  Once this is completed, we develop and publish an installation template for that accessory.  Click Templates for a listing of certified components.

21. If we have to use your splices and termination all the time, do we need special training for our technicians and if yes can you provide such training and at what cost?

Novinium does not require special splices and terminations for future repairs.  We only require that accessories we use will work properly with our injection adaptors — not all qualify.  If you replace anything that Novinium installed, you can replace it with any standard accessory you may normally use.  Any information you require to be confident of what action to take is provided in detail within the Novinium Rejuvenation Instructions or NRIs. Novinium sets the standard for craftsmanship and we will soon be sharing our expertise with the world.  Watch for an announcement soon of an online craftsmanship training course at www.knovinium.com.  Even if you don’t rejuvenate your cable, you should be learning from the world’s foremost reliability experts the best way to install components.

22. Did you type test your splices and terminations and are they certified to be used in such applications?

Yes, the accessory manufacturer has type tested all splices and terminations certified by Novinium. Further, Novinium tests each splice and termination to be certain that they will work with the Novinium injection adaptor. Once this testing is complete, Novinium publishes a template for that accessory at Templates. Many of the accessory manufactures have also reviewed the Novinium templates and procedures and have issued letters indicating that the Novinium technology is compatible with their components.  See Certified and click on Hubbell, Cooper Power Systems, 3M, Richards Manufacturing, Prysmian, or Tyco/Raychem to view letters from the component manufacturers.

T. B. Frog

Middle East Query – Ampacity Impacts

Dweller of the Desert asked 22 questions in his post …

Middle East Query – 22 Questions.

In this installment I address question 17.

17.   Does injection have any impact on cable ampacity?

Cable injection, per se, has no effect on the cable ampacity.  Filling the small interstitial spaces between the strands with a liquid has no measurable effect.  However, the swaging technique utilized by Novinium crews and our partners is state-of-art and the terminations and splices will run cooler than those they replace.  The summary conclusions above were confirmed by testing performed by the National Electric Energy Testing, Research & Application Center (NEETRAC) at the Georgia Institute of Technology U.S.A. Click here to view the full report for NEETRAC Project Number 09-019 of April 2009, “NEETRAC Thermal Testing of Novinium Feeder Cable Splices on Service Aged 750kcmil XLPE Cable Extracted from the Georgia Power System.”

For now, Ma’a salama (مع السلامة/Good bye)

T. B. Frog

Middle East Query – Water-Block and Rejuvenation

Dweller of the Desert asked 22 questions in his post …

Middle East Query – 22 Questions.

In this installment I address question 16.

16.   What if my cable strands have water block design elements?

If a cable has thermoplastic strand fill material or has water absorption powder, it probably cannot be injected.  However, these materials were not generally adopted until about 1985.  It is unlikely that cables, which are suffering reliability issues, have strand-blocking features.  When the Novinium process is used to inject cables, the Novinium Injection Adaptor is used to tenaciously seal the ends of the cable and each splice.

For those circuit owners that specify strand-blocked cable – stop!  The cable manufacturers charge you more, but for what benefit? An understanding of how water distributes itself in a cable provides no justification for the additional expense.  Click here to read an article in the November/December Issue of IEEE Electrical Insulation Magazine, “Molecular Thermodynamics of Water in Direct-buried Power Cables.”  The “Molecular Thermodynamics” article provides data and a theoretical framework to understand the negative impact of stand-blocked conductor designs.

For now, Ma’a salama (مع السلامة/Good bye)

T. B. Frog

Middle East Query – Certification & Standards

Dweller of the Desert asked 22 questions in his post …

Middle East Query – 22 Questions.

In this installment I address question 15.

15.   Does Novinium have any type/kind of certification?

Novinium is a leader in creating a rejuvenation industry specification. I wrote about our effort in my 2010, December 16 post:

Draft Guide for Rehabilitation and Rejuvenation of Extruded Dielectric Cable Rated 2.5 kV through 46 kV

Click here to go to the gateway to the Draft Guide. Novinium also provides detailed Novinium Rejuvenation Instructions (NRI) at:

http://novinium.com/Instructions.aspx

… and accessory templates at:

http://novinium.com/Templates.aspx.

These detailed instructions and templates must be followed on each injection project to insure that the work is carried out correctly. This is how Novinium insures work quality.  Novinium also certifies each injection technician before allowing them to work alone.

Finally Novinium’s patented (U.S. Patents 7,195,504, 7,538,274 and 7,683,260) Injection Adaptors (IAs) have been tested to ANSI C119.4.  Click here to see “NEETRAC ANSI C119.4 tests of Novinium Injection Adaptor.”

For now, Ma’a salama (مع السلامة/Good bye)

T. B. Frog

Middle East Query – Novinium Research Papers

Middle East Query – Diagnostic Testing Timing

Dweller of the Desert asked 22 questions in his post …

Middle East Query – 22 Questions.

In this installment I address question 13.

13.   Can the customer test the cable right after injection? Could it be done immediately? If not, after how many days, weeks or months?

You are not going to like my answer, but this frog is incapable of subterfuge. There are no cable testing methods that will tell you when a cable will fail, which is what you really want to know. At best, testing will provide you a number you can track over time. An extensive U.S.A. study, the Cable Diagnostic Focused Initiative (CDFI) led by NEETRAC (The National Electric Energy Testing Research & Application Center at Georgia Tech’s College of Engineering) of commercialized cable testing methods came to this conclusion—see CDFI slide 41. The CDFI is the largest and most comprehensive study ever undertaken. All cable testing methods, except online PD testing, can cause damage to the cable insulation and shorten cable life.  Some cable testing methods such as Tan Delta or Power Factor are not comparable before and after injection, because cable injection alters the chemistry and physics of the cable, changing the measured parameters in ways counter to the claims of the diagnostic supplier.  See my 2010, September 10, post, “Cable Rejuvenation Impact on Loss Factor (tan-Delta).” In one example from that post, the tan-Delta at 0.1Hz increased after treatment, even though dielectric strength increased substantially – just the opposite of what the proprietors of the test predict. Because available diagnostics do not provide useful information and/or the tests are inherently destructive, Novinium discourages cable testing before or after cable injection. If a circuit owner chooses to test its cable despite overwhelming evidence of futility and counter productivity, before or after injection, Novinium will suspend, but not extend, any warranty for 120 after the test. Make sure you check out my 2010, November 12 post: Diagnostic Testing – Should I do it? One sneaky way to test the veracity of diagnostic firms’ claims is to request a warranty for cables which test as good, but fail. And when I say warranty, I don’t mean a credit for future diagnostics – I mean money back.  In a three-year experiment undertaken as part of the CDFI to measure the accuracy of online partial discharge testing, false negatives were about 9.5% and 19.5% for accessories and cable respectively.  False positives were 69% and 56% respectively.  I can do better than that with a role of the dice!

For now, Ma’a salama (مع السلامة/Good bye)

T. B. Frog

Neutral Corrosion Progression

Two of my disciples inquired of my July 7, 2010 post, Neutral Corrosion – How much is too much?

Dear Sheila and Kurt-

There are several different mechanisms for cable neutral corrosion.  The mechanisms are enumerated in Section 6 of IEEE 1617-2007 "Guide for Detection, Mitigation, and Control of Concentric Neutral Corrosion in Medium-Voltage Underground Cables." My colleague, Glen Bertini, was one of the participants in the ICC C7 working group that developed that document. The identified mechanisms of cable neutral corrosion in section 6 are:

1.   Galvanic corrosion

2.   Single metal corrosion

3.   Soil corrosion

4.   Differential aeration

5.   Stray currents

6.   Galvanic corrosion resulting specifically from tin coated neutral wires

Of these possible causes of neutral corrosion, soil corrosion and differential aeration are by the far the most predominant and problematic.  In both cases differences in soil chemistry along the path of the cable lead to differences in potential on exposed neutrals. Current flows in a loop through the soil and along the neutral. Copper is oxidized where the electrons leave the neutral and enter the soil and where there is oxygen (or sulfur) present. The rate of corrosion is a function of the current flow and is constrained by the availability of oxygen. Current flow, in turn, is proportional to the potential difference caused by the local differences in soil chemistry and inversely proportional to the resistance of the loop.  In the illustration nearby I show how this all works. Either from differential aeration or differences in the local soil chemistry the electrochemical potential is higher at point A than it is at point B.

As the neutral corrodes, the resistance in the loop goes up, which slows the rate of corrosion. The loss of the metallic copper itself leads to an increase of resistance. Less obviously, the non-conductive corrosion by-products (i.e. copper oxides) coat the copper surface and increase the resistance between the neutral and soil. Another set of chemical processes determine how quickly the copper oxides are transported off of the native copper surface below them. This copper-oxide transport mechanism is typically very slow in direct buried environments as the oxides are not appreciably water soluble.

At the same time the resistance is increasing, the second law of thermodynamics is at play reducing the chemical potential difference between A and B. The homogenization of chemical potential over time would occur whether or not a cable was present. Nature abhors chemical potential differences so chemical species migrate through the soil toward equilibrium – zero chemical potential difference.

Corrosion of bare concentric neutrals is highest when the neutrals are new and the soil was disturbed when the cable was installed. As some corrosion occurs and the second law reduces the chemical potential, the rate of corrosion decreases over time. In practice if the neutral has at least partially survived for several decades the rate of continuing degradation is trivial.

The other causes of neutral corrosion are much less prevalent. With the possible exception of stray currents impressed upon neutrals by active cathodic protection systems of neighboring structures (e.g. gas pipelines), all are similarly mitigated by the partial corrosion of the neutral and the equilibration of chemical potential due to the inexorable second law of thermodynamics.

If cows dragged their bulging bellies across the ground as I do they would be safe from stray current. Even with a substantial potential at the ground surface, I remain equipotential. If cows or other mammals are getting electrocuted the neutrals are entirely destroyed either locally or systematically. If the corrosion is systematic, the cables must be replaced. The source of the systematic corrosion should also be identified and eliminated – it’s not a natural phenomena; it’s man-made. Dead cows are the odd cases, but these cases get media attention, so the anecdotes are oft repeated.

In the real world, most concentric neutral corrosion is incredibly local. One or two feet of neutral become corroded. It turns out this problem is easy to diagnose and easy to repair. Diagnostic techniques are described in the aforementioned IEEE 1617-2007. A step-by-step and state-of-the-art procedure is available for free from Novinium Rejuvenation Instruction 12 (NRI 12), Electronic Cable Diagnosis and Pinpointing. Also free are step-by-step instructions (NRI 80), Neutral Corrosion Repair, that make fixing local corrosion a piece of cake. Once a local corrosion site has been pinpointed, chemistry can be employed to protect the location of the identified chemical potential difference. A suitably sized magnesium anode that has a chemical potential well above that of copper is installed as a sacrificial anode. The anode size can be adjusted to prevent neutral corrosion for any desired life.

Over twenty years of rejuvenation experience with a dearth of warranty claims in general and even fewer neutral corrosion issues specifically, provide direct evidence that whatever post-injection progression of neutral corrosion that does occur is of little practical significance.  At Novinium we have had zero failures and zero warranty claims that involved an increase of neutral corrosion after the cable was treated.

Equipotentially yours,

T. B. Frog

Middle East Query – Rejuvenation Saves Capital

Dweller of the Desert asked 22 questions in his post …

Middle East Query – 22 Questions.

In this installment I address question 12.

12.   What is the expected cost of curing compared to cable replacement?

Typical costs for injection are one-half to one-third of the cost of cable replacement.  For submarine cables and armored cables, cable injection can be only one-sixth the cost of replacement.  With soaring costs for copper, aluminum, and petroleum-based polymers the economics of injection only get more compelling.  In addition to raw material costs, skilled craftsman to replace cables are becoming increasingly scarce and more costly.  Rejuvenation requires one-half to one-third of the labor-effort to replace a length of cable, so the cost to rejuvenate will always be proportionally less than replacement.  With the state-of-the-art sustained pressure rejuvenation process, even cables in ducts, conduits, or trays enjoy the cost advantage of rejuvenation. Because splices are either non-existent or easily accessible in these systems, the rejuvenation productivity remains two to three times higher than replacement. Hence the cost to deliver rejuvenation remains below the cost of replacement.  Finally, the funds expended for cable rejuvenation are capital cost – just as cable replacement is a capital cost.  In fact, Novinium technology is the only cable rejuvenation that the FERC (U.S. Federal Energy Regulatory Commission) and the RUS (Rural Utility Services) have approved to be capitalized for post-failure treatment.  Check out the FERC Letter Order and the RUS Letter Order for more details.  Saving capital is what we do.  Technology invented by Novinium founders has saved circuit owners around the world over one billion U.S. dollars!

For now, Ma’a salama (مع السلامة/Good bye)

T. B. Frog

Middle East Query – Reinjection? Re-rejuvenation?

Dweller of the Desert asked 22 questions in his post …

Middle East Query – 22 Questions.

In this installment I address question 10.

1.   Can injection be carried out twice on the same cable after 10-20 years of the first injection?

When Novinium^® Ultrinium™ brand fluid is used there is no need to reinject after 10-20 years. Even in the most demanding conditions, including the hyperthermic soils of the Saudi Arabian desert, Ultrinium fluid will extend life for four decades or more. Ultrinium technology enjoys a patented Novinium innovation (U.S. Patent 7,611,748), which involves the tailoring of the fluid formulation to the specific and unique requirements of the each circuit. Older generations of injection technology such as Perficio™ fluid, which cannot be tailored to demanding hyperthermic conditions, would need to be replenished after a decade or so.  Novinium has successfully re-injected cables after 10-15 years that were previously injected with CableCURE^®/XL fluid. Novinium developed the patent pending N-Ter™ process to facilitate the re-injection of cables. Check out a case study at Littleton Electric Light in Massachusetts, U.S.A.  The procedures for N-Ter injection are available online at N-Ter™ Technology.  In short, the conductor is warmed with a low voltage current source.  The warmer conductor reduces the viscosity of the old fluid remaining in the strands and expands the conductor strands creating more interstitial space.  Innovation makes all things possible – safer, faster, better.

For now, Ma’a salama (مع السلامة/Good bye)

T. B. Frog

CableCure is a registered trademark of UTILX Corporation.