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

Reflections on a TDR

Dear Thermo,

The blog entitled "Neutral Corrosion - How much is too much?" includes a waveform from a TDR (time domain reflectometer, often called a radar) that is used to pinpoint bad sections of cable neutral. The TDR is also used to pinpoint splice locations on the cable. Please provide the details of how the TDR determines the neutral corrosion and splices on the cable and how the wave form is read to tell them apart and to pinpoint their locations.

Reflective in MD 

Dear Reflective-

Step-by-step instructions for how to identify and pinpoint neutral corrosion and splices on concentric medium voltage power cables are provided in Novinium Rejuvenation Instruction 12 entitled, “Electronic Cable Diagnosis and Pinpointing.” Click NRI-12 to view the document as a PDF. The TDR sends a low voltage (10-20 volts), short wave length (1-20 nanoseconds) pulse down the cable. A portion of the wave is reflected when it encounters a change in impedance. There are four main types of impedance changes encountered along the length of a test cable.  Remember – impedance includes three elements, resistance, capacitance, and inductance. 

(1)       Instrument-Cable Interface

The first impedance change that is encountered results from the mating of the test instrument lead, an RG59 coaxial cable, which has a characteristic impedance of 75 ohms, with the power cable, which has a characteristic impedance of 8 to 38 ohms depending upon its geometry and polymer system. To minimize the reflection from this unavoidable impedance change, the masters of reliability at Novinium use a proprietary impedance streamliner. This is akin to an aerodynamic sports car versus a squarish pick-up truck. The impedance streamliner is like the smooth curves of the sports car, reflecting less of the input pulse, minimizing signal attenuation and dispersion. Attenuation is the reduction of signal amplitude and dispersion is the smearing of narrow pulse into a broader, less discrete pulse. Both are undesirable. Some reflection is unavoidable. The signature of Novinium’s impedance streamliner shown in red is superimposed upon the green signature of an older impedance technology device (ITD) in the image nearby. Untoward noise and reflections avoided improve the usability and hence the sensitivity and accuracy of the TDR.

(2)       Splice 

In the image nearby I am standing next to a very typical splice during a recent coffee break. The neutrals are all dirty as they are prone to be in a pit, but if you look carefully along the orange annotation, you can see how the neutrals are close to the conductor on the cable, then are pig-tailed together and lay farther from the conductor as they jump across the molded splice body. On the far end of the splice the neutrals again come back to intimate proximity. This change in the separation of the two signal conductors – the conductor and the neutral – changes the circuit impedance. The resistance is not significantly changed, the already low capacitance decreases with increasing distance, but that capacitance change is trivial compared to the change in inductance. The inductance and hence the impedance skyrockets as the neutrals leave the insulation shield and then plummets when the neutrals return to the cable. I have superimposed the actual TDR image of a splice, a characteristic sine wave, in the lower-right-hand corner.

(3)       Neutral Corrosion

The physics are even simpler for neutral corrosion. The capacitance and inductance components are insignificant. A good old-fashioned resistance increase is displayed as an impedance increase. Check out the nearby image.

(4)       End-of-cable

Simpler still, the end of the cable is characterized by either an infinite impedance increase if the circuit is open or an infinite impedance decrease if the conductor is grounded to the neutral. When used, grounding devices add some more color to the wave shape, but the basic idea remains the same.

The TDR signal is reflected by each of the above impedance changes and the time the signal takes to travel to and then from the impedance change can be used to estimate the distance to that change. Note that the TDR is not a pinpointing technology, it provides a location estimate. To pinpoint splices and corrosion a second technology, radio-frequency (RF) locating, is utilized. If you desire, I will be happy to explain how that works too. NRI-12, described earlier, provides step-by-step instructions to accomplish RF pinpointing.

Your adroit amphibian,

T. B. Frog

Flowing Through Splices

Dear Wisest of Frogs,

We have been proactively injecting cables with the unsustained pressure rejuvenation for years.  Many of the cables we seek to treat have existing splices and we have always attempted to flow through the encountered splices. I understand that Novinium will use the same approach if required by the circuit owner, but you seem to frown upon the practice. Why the frowning face? Why will you inject through splices if you don’t think it a productive practice?

Seeking the easy way,

Qui Transtulit Sustinet

Dear Sustinet-

Any state that has a Latin motto is a state near and dear to me! The most common translation of the Connecticut state motto is, “He who is transplanted still sustains.” And what the heck is that supposed to mean?  The origin of that motto is uncertain, but with my skills in Latin, I have an alternate translation that better captures what its framers had in mind – to wit, “A splice replaced is more reliable.”

There are three inherent uncertainties about flowing through unexcavated direct buried splices.  The first uncertainty: One seldom knows what kind of splice is there. Design and compound chemistry are the most common uncertainties. Splices might fall into one of three categories – okay, bad, and ugly.

The second uncertainty is the quality of the craftsmanship that went into the splice.  Some circuit owners have had very few component failures.  Is your firm one of the lucky few?  Novinium’s master craftsmen are all trained and certified to exceed the emergent IEEE P1816™, “Guide for Preparation Techniques of Extruded Dielectric, Shielded Cable … and the Installation of Mating Accessories.”  Novinium had a hand in the creation of the P1816 Guide and is the only firm in the world that offers training and certification to the Guide. Novinium shares this knowledge on its eLearning website at www.knovinium.com.

Finally, while air pressure tests are typically employed to confirm that a splice or splices in a cable will support a minimum anticipated pressure, it is not possible to know with certainty whether rejuvenation fluid, with its inherently low surface tension, will leak across the splice-cable interface. The leaking of a dielectric fluid across an interface has one certain issue and two potential issues.

• Certain issue: The quantity of fluid intended to treat the cable insulation polymer will be less than planned. If the leakage is significant, such a leak will reduce the anticipated post-injection life of the cable.
• First potential issue: Leaking fluid may carry particles, such as suspended carbon black or aluminum oxide, along the splice-cable interface. Such particles may contribute to interfacial tracking.
• Second potential issue:  Rubber splices absorb a substantial amount of treatment fluid intended to treat the cable.  This phenomenon was described in the November 1, 2005 paper “Improving Post-Treatment Reliability: Eliminating Fluid-component Compatibility Issues” presented at the ICC C26 Discussion Group. Click here to get a complete picture of this issue.

The Novinium masters of reliability seek the unattainable – perfection – 100% post injection reliability.  We are at 99.4% today and climbing. See Crow for the data. If you are attracted to the idea of kicking today’s problems down the road for your successors to deal with, you might want to consider a career in U.S. national politics. The electorate has a proclivity to elect folks that are unwilling to deal with problems, even when they are easy to recognize. Unlike the beltway crowd in D.C., this frog doesn’t believe in kicking today’s issues down the road only to address them again later – fix it, fix it right, and fix it right now!

To circuit owners, I dispassionately explain the economics of the two approaches and do a little cheer for the most economical approach.  The circuit owner decides and I say, “Yes, ma’am!” At the end of the day, some circuit owners are devoted to a less enlightened path. I believe this is generally so because of inertia.  That is, flowing through splices has been practiced for two decades, and it works decently enough. The economics are more favorable than replacement alone. Once circuit owners experience the more enlightened Sustained Pressure Rejuvenation (SPR) approach and get a chance to enjoy its benefits, it is generally embraced.

In a future post I will explain Integrated Rehabilitation, which is the ultimate approach to rehabilitating underground cables.

Reliably Enlightened,

T. B. Frog

 Splice Quandary

 Dear All-knowing Frog,

My firm’s cable system consists of cable segments with existing hand-taped splices and “Dutchmen” type splices.  Describe how your company would inject cables with both these types of splices and the benefits\cost savings.

Can you help me with my splice quandary?

Al Berta

Dear Al-

You came to the right Frog.  Many circuit owners reflexively think about replacing the entire cable run when a single blocked splice is encountered. Replacement of the entire run is the least capital efficient approach.  To understand why this is so, check out my August 31, 2010 post “Of Splices and Prices.”

Dealing directly with splices is definitely the way to go. Novinium is the only rehabilitation supplier that offers three solutions – a good solution, a better solution, and a best solution.

Good

Traditionally, when blocked splices (or splice pairs a.k.a Dutchmen) are encountered they are excavated and replaced.  They may be replaced with a molded repair splice, where the repair splice length is great enough to span the gap between the two cable ends, or a pair of regular length molded splices together with a length of stranded and non-strand-blocked cable. Hose clamps are included on the molded splices to provide added hoop strength and improve their pressure holding capability.

Better 

Using Novinium’s patented (U.S. Patents 7,615,247, 7,195,504, 7,538,274, 7,683,260, and their non-U.S. equivalents) sustained pressure rejuvenation (SPR) process, splices are replaced with almost any kind of splice and the cable is injected from the splice pit in both directions, back to the next cable end.

Best

Combining the “pros” and eliminating all but one “con” of the good and better splice solutions is the Novinium flow-through splice. Shown in the drawing nearby a simple modification of a standard 3M compression connector makes for a flow-through splice without any pressure limitations. With the Novinium flow-through splice the cable can be treated with UPR or SPR methods and there is zero loss of fluid to the component.

Benefits and Savings

Novinium is the only firm with all three of these tools in its toolbox.  I’m reminded of Maslow’s hammer, popularly phrased: “If all you have is a hammer, everything looks like a nail.”  If Novinium had only the “Good” approach, the circuit owner would have to accept the “Cons” associated with that approach. Instead, Novinium chooses the right tool for any circumstance – the tool that minimizes the time required to inject (i.e. saving money) and maximizes the post-injection reliability.

With options that can be tailored to your needs,

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

Dweller of the Desert asked 22 questions in his post …

Middle East Query – 22 Questions.

In this installment I address question 8.

8.   How do you rejoin cable ends after an old splice is removed?

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.  Depending on the circumstances there are several ways to replace existing splices:

a.   Carefully remove the current splice body covering and split off the current connector.  Using our special connector cut-off tool it is possible to preserve the existing conductors.  In many cases a non-repair connector and splice can be installed to replace the old.  If some slack is needed to complete the repair a longer repair connector and a repair length spice can be installed.

b.   Cut out the current splice and replace it with two splices and a short piece of cable in between. This method is generally required for hand-taped splices, where there is legacy damage to the cable within or near the splice, or where a significant amount of slack is desirable.

c.    I-Joints, J-joints, and H-joints are available for multiple cables spliced at one point.  Such modular joints are inherently longer than other splice types.

No matter which of the choices above are executed the cable-connector interface is permanently sealed to keep rejuvenation fluid in and water out with Novinium’s injection adaptor or IA.  The IA enjoys three U.S. Patents (7,195,504, 7,538,274 and 7,683,260) and their non-U.S. equivalents.

Pride is a sin unless you are a craftsman.  Novinium’s craftsmanship is without peer.  We were leaders in the pending IEEE P1816™ “Guide for Preparation Techniques of Extruded Dielectric, Shielded Cable Rated 2.5 kV through 46 kV and the Installation of Mating Accessories.” We are the only source in the world for training compliant to the emerging P1816 guidelines.  Check out our e-learning site at knovinium.com.

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

T. B. Frog

IEEE P1816 is a trademark of the Institute of Electrical and Electronic Engineers.

Dweller of the Desert asked 22 questions in his post ...

Middle East Query – 22 Questions

In this installment I address questions 4 and 5.

4.   How much time does it take to inject a certain length of cable?  What is the maximum cable length that can be injected?

The longest cable to date that Novinium has injected was 4,400 meters.  This was a 53 mm² compact strand submarine cable out to an island.  Check out the aerial photograph.  The cable path was at a maximum depth of 500 meters.  We know how to go much longer.

Injection times are dependent on:

a.   Insulation material—XLPE injects faster than EPR

b.   Strand compaction—round strands faster than compact or compressed strands

c.    Cable size—larger cables inject faster than smaller ones, because there is more space between the strands

d.   In general, a 100 meter piece of cable injection requires less than 30 minutes.

If you have a specific long cable in mind, give me the particulars and I can show you how we calculate how long it will take.  There is also a June 27, 2007 paper, “Advances in Chemical Rejuvenation of Submarine Cables” that explains the basics.

Novinium provides the technology to identify the number and location of buried splices.  The number and approximate location of splices can be determined in less than 15 minutes with a time domain reflectometer or TDR.  Buried splices can be accurately located in 1-2 hours depending on access to the cable path and the number of other cables in the same area with a radio frequency locator or RF locator.  We describe how this is accomplished in Novinium Rejuvenation Instruction 12 (NRI12).

A TDR sends an electronic pulse down the cable.  Changes in impedance create reflections that are displayed on the instrument as wave forms.  It is important to use an impedance streamliner (IS) to minimize the reflections at the connection between the TDR and the cable.  The photograph nearby shows a Novinium proprietary IS and a high resolution TDR.  The inset shows a TDR in use by a master craftsman.

The illustration below shows how a splice is pinpointed with a RF locator.  A signal is impressed between the conductor and the concentric neutral.  The two signals are 180° out of phase, so they tend to cancel each other out.  I say they tend to cancel, because the canceling is not perfect and some signal leaks through allowing the master craftsman to follow the cable path.  The signal strength typically skyrockets when the craftsman nears a splice, because the concentricity of the neutral is generally disturbed at the spice.

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

T. B. Frog