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

O-ring Evolution

Dear Erudite Amphibian,

If an O-ring equipped probe of an injection elbow were to break-off or otherwise fail, can we replace it with a standard probe?

Wondering in Washington

Dear Wondering-

The absolute best choice is to replace the damaged probe with an identical probe. Novinium would be happy to provide these probes to you with only a modest markup. If the Novinium masters of reliability are in town, just give them a call as they likely will have spares on their truck. This frog realizes that your question is probably targeting the case when there are none of these O-ring equipped probes nearby and you desire to put the cable back in service. To answer that question it is useful to explain how the O-ring-equipped probe evolved.

In the illustration nearby, I point at a fully evolved O-ring on a probe pin.  In this 2011 incarnation the O-ring is seated in a composite sleeve molded into the elbow throat. The very first injection elbows were invented by my colleague, Glen Bertini and his associate at Dow Corning, Dan Meyer, about 25 years ago.  I wish I had a picture to show you, but I don’t believe any exist of that dinosaur.  The very first injection elbow, used from 1987 to 1989, was a standard elbow with a capacitive test point.  Bertini and Meyer drilled and taped a hole through the capacitive test point and screwed an insulating nylon cap into the hole.  The elbow worked flawlessly, but was properly considered unreliable for long term operation and hence the elbow was treated as a tool.  After the injection was complete the modified elbow was swapped for an unmodified elbow of the same size. There was no O-ring in either elbow.  CableCURE^® 2-2614 fluid, which was (and remains) predominately phenylmethyldimethoxysilane (PMDMS) and has a flash point of about 66°C flooded the bushing on 100% of the applications.  There were no adverse consequences observed.

The next improvement in the injection elbow was the introduction of a dedicated interference fit injection port.  The collaboration between Bertini and Meyer of Dow Corning and Alan Borgstrom of Elastimold yielded two U.S. patents, 4,946,393 and 5,082,449 in 1989 and 1990.  This advancement meant that the injection elbow could be left in place indefinitely … only the injection cap had to be swapped. There still was no O-ring, hundreds of thousands of feet of cable were injected, and there was precisely one problem. Sometime in late 1989 a bushing failed because the CableCURE 2-2614 fluid had dissolved a plastic component within the bushing. Elastimold and Dow Corning immediately tested the fluid and bushing component compatibility and found no issues that detracted from the elbow-bushing compliance to IEEE 386™.  See Elastimold test reports 102-17-9011 and 101-17-9010, both dated January 1990.

168 1990 (102-17-9011) - IEEE 386 15kV with fluid.pdf (135.13 kb)

274 1990 (101-17-9010) - IEEE 386 25kV with fluid.pdf (134.51 kb)

It turns out the single bushing that failed was an anomaly – not a large production bushing. None-the-less, Dow Corning and Elastimold decided that even though incompatible bushings would be a rarity, it would be prudent to add a seal to the system to minimize the probability of adverse fluid interactions within the bushing.  An O-ring was added to the probe in about 1991.  The rubber O-ring was not seated in a rigid collar and hence a small deflection of the probe pin would allow a leak. This problem was minor, however, because when the elbow was seated on the bushing it was held in a perfectly centered position.

Two years later in about 1993, UTILX^® Corporation, after licensing CableCURE technology from Dow Corning, unveiled another Bertini inovation (U.S. Patent 5,372,841), which was called CableCURE^® XL fluid. While XL fluid brought significant dielectric performance gains, it suffered from a much lower flash point and it wasn’t too long before the imperfection of the O-ring seal lead to fires when a fluid-filled elbow was switched.  Over the course of the next decade, the seal was changed several times to improve its robustness.

Novinium fluids are not flammable. See my November 2, 2011 post “Fluid Flammability” for more on this subject. If you are using a flammable fluid from another supplier, this frog would highly recommend using only O-ring probes.  With Novinium fluids the risk is minimal.  There is a low risk that fluid will get into the bushing after the injection has been completed, and that risk decreases as time-since-injection advances.  There is an even lower risk that Novinium fluids in the bushing will create any safety or reliability issues.

In 2012 Novinium and our component manufacturing partner will be introducing an entirely new injection device suitable for both unsustained pressure rejuvenation (UPR) and sustained pressure rejuvenation (SPR).  It will be inherently leak-free. When the new injection device becomes commercially available, switch to it and your question will become moot.

Evolving to be safer, faster and better,

Thermo

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

Soaking I:  Diminishing Returns

Dear Greatest of Soakers,

It seems odd to me that for one who spends so much time soaking herself, that soaking cables is anathema to your firm’s culture.  When is it appropriate to soak a No.2 compressed URD cable?  If I do soak, for how long should I soak?

Geometrically constrained,

Alaskan Amber

Dear Amber-

You ask more questions than any of my other numerous fans.  I like that, except I have been told that some find the questions and the answers too technical.  My response to those critics is to ask your own questions.  If you ask a simple question, I will provide a simple answer.  This Amber guy is cool, his question is appropriate, and a proper answer it is going to require two posts.  Here is the first …

I can see why you might have been misled to believe that I am anti-soak, but that characterization is unfair.  Let’s set the facts straight:

1.   Novinium has a pile of patents that make soaking unnecessary, even for multi-decade life, for all but the most geometrically constrained cables.  I will define “geometrically constrained” later.  The following technological advancements, which I have expounded upon in past blogs, mean that even without a soak, Novinium technology will last longer than the two-decade old approach used by less enlightened purveyors of rejuvenation:

a.   Catalyst improvements were chronicled in Catalytic Considerations I and Catalytic Considerations II.

b.   Novinium Voltage Stabilizers are not present in older approaches.

c.    Our ultra-violet package, which retards the formation of electrical trees was laid out in “To UV or not to UV.”

d.   The tremendous power of effective anti-oxidants present only in Ultrinium™ brand fluids was described in “AO, AO … its home from work we go.”

e.   “Chain Entanglement” dramatically slows the exudation of treatment fluid from the cable and is another patented Novinium innovation.

f.     The “Really Long Term Life” afforded by still another patented Novinium innovation delivered by an ultralow permeability component.

2.   The folks at Novinium invented soaking over two decades ago.

3.   Novinium does soak cables under certain circumstances.

We do consider soaking as a last resort, however, because soaking has two drawbacks.  First, and in order of importance to us, there are safety compromises associated with leaving a hydraulic connection to an energized cable for a long period of time.  I enumerated these risks in my post:  “Greatest Rejuvenation Risks.”  For live-front applications, Novinium can greatly mitigate these risks with a piece of proprietary technology called an HVFI or high-voltage fluidic-interface.  Click here to view a HVFI test report.  Second, there are economic costs associated with a soak period.  In short, a soak bottle with an associated capital cost must be deployed for the duration of the soak period and the injection team has to be redeployed to the site to remove said soak bottle.

Despite these challenges we occasionally resort to soak periods.  The very first consideration is whether the cable to be rejuvenated has a severely constrained geometry.  The “Draft Guide for Rehabilitation and Rejuvenation of Extruded Dielectric Cable” defines constrained geometry in general and severely constrained geometry in particular as follows:

“When the available volume of fluid that can be held in the strand interstices at atmospheric pressure is less than the optimum quantity of fluid to treat the cable, the cable is said to be a constrained geometry cable.  Figure 3-1 [below] shows the three realms of geometry for round (or concentric), compressed, and compact strand cables, namely unconstrained (greater than 20 kg/km), moderately constrained (<20 kg/km and >10 kg/km), and severely constrained (<10 kg/km).”

In practice severely constrained cables are those with conductors of 7-strand and compact 19-strand construction.  If your cables do not have severely constrained conductors, four decades of life extension are possible without resorting to soak periods.

At Novinium we routinely employ soak periods on severely constrained geometry cables for high value circuits with live-front terminations.  Submarine cables provide an example of such high value circuits.  These cables can require 7-figures to replace, so the incremental cost of providing a soak is justified.  Can Novinium make soaking safe in the dead-front applications typical of residential distribution cable?  To answer that question check out my subsequent posts in this series:

Soaking II:  Safety First

Unconstrained by old paradigms,

Thermo

Fan the Strands

Dear Greatest Amphibian,

I have a question regarding a statement I heard one of your colleagues make at an ICC meeting recently.  Would you comment on the criticality that wire brushing of the conductor has when installing a connector?

Kindest regards,

JA at Xcel-lent

Dear JA-

You are indeed Xcel-lent because you are not afraid to ask the tough questions.  And I am Xub-erent, because I love to dispel myths.  When connectors are qualified to ANSI C119.4 do you think the manufacturers use old corroded conductors?  If you answered yes, stop reading here.  If you answered no, read on. More...