Deep Creep

Dear Deep Diving Frog,

I was reading a paper on your web site “Silicone Injection: Better with Pressure” that was discussing fluid pressures that different cable insulations could withstand. The testing was done at Florida Power and Light and showed that XLPE cable could withstand up to 750 PSI before bulging and approximately 650 PSI before a point of inflection was reached where deflection accelerates with further pressure increases. The pressure was increased 50 PSI every 15 minutes. Have any sustained pressure tests been performed on XLPE cables under the pressures that will be used for submarine cables, since the pressure will be sustained for months?  Also, I assume that shore ends will be a bigger concern for pressure impacts than deep water sections where the weight of the water will be pushing back on the cable?

Regards,

Concerned about Creep

Dear Concerned-

Editors note:  I had to fight my froggy urge to respond "Dear Creep."

Nearby, I have reproduced Figure 5 from the “Better with Pressure” paper, to which you refer, except I embellished it with my lovely image.  I would encourage my other readers to immerse themselves in the entirety of that paper.  First, I must make an important correction to your question.  The insulation of the cable in Figure 5 was uncrosslinked HMWPE or high molecular weight polyethylene.  Cross-linked polyethylene or XLPE has significantly better mechanical properties.  In fact, similar sized XLPE cables were injected “on-the-reel” by Hendrix Wire & Cable in the late 1980’s at pressure of 750 to 1000 psig.  See Table 1, the accompanying text on page 2, and references [5] and [6] of the “Better with Pressure” paper.

The inflection point at 650 psig is labeled as such in the figure. Up to 650 psig the difference in the inside pressure and outside pressure increased the diameter less than about 1.5% – this is less than the diametrical deflection caused by a temperature cycle to the cable’s design temperature.  However, once this inflection point is reached, polymer bonds are actually broken and the diameter change is not entirely reversible. That is, the diameter does not return to its original value when the pressure is removed. Of course, this frog would never get close to the inflection point … we stay below this point by a factor of at least three!

We have not done laboratory experiments with multi-month injection periods, but we have something even better – multi-month operational experience.  At a meeting of the Insulated Conductors Committee (ICC) on May 19, 2009, my colleague, Glen Bertini, made a presentation titled “Lessons in Submarine Cable Rejuvenation” in the C11 discussion group.  Slide 14 of that presentation describes an injection of a 14,432 foot, 1/0 compact, 25kV XLPE cable crossing Desolation Sound in beautiful British Columbia.  Desolation Sound is about 1,500 feet deep at that location.  The fluid took about 100 days, or over three months, just to reach the other end. The injection pressure was about 300 pisg. Several years later the cable remains in operation.

Willing to dive deep, but never creepy,

Thermonuclear

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

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

Catalytic Considerations – Component I

In my December 29, 2010 post at …

Crazy-Competitor-Claims

Wonderer in the Wilderness inquired …

1. How can Novinium get the same cable life extension without a soak period?  It would seem to me that Novinium puts less fluid into the cable than one would get with a soak period.

In the previous post, I provided an abbreviated answer; in this post I will provide a more comprehensive answer.  We learned from the abbreviated answer that when Novinium founders conceived of the first generation of treatment fluid over two decades ago, we failed to check the relative diffusion rates of the phenylmethyldimethoxysilane (PMDMS) monomer and the condensation catalyst we chose to provide long life.  In the figure nearby, I show diffusion data that demonstrate that the monomer diffuses about six times faster than the catalyst.  I also show two-dimensional scale representations of these two molecules.   From what we learned in Size Does Matter, one can see that the larger and less flexible titanium(IV) isopropoxide (TIP) molecule would diffuse slower than the PMDMS and it does.

This diffusion mismatch was a tragic mistake, because the monomer does not condense to a longer molecule in the absence of a catalyst.  As a consequence, a substantial portion of the PMDMS diffuses out of the cable shortly after injection without adding to the long-term reliability of the cable.  In fact, about 39% diffuses out prematurely.  This premature exudation is caused by catalytic inefficiency.  We cleverly fixed that problem with U.S. Patent 7,700,871, and I will explain the elegance of that solution in a subsequent post in this series …

Catalytic Considerations – Component II

It isn’t just how much fluid is delivered to the cable strands.  Even more important than the fluid quantity injected are:

1.    The amount of fluid that persists in the cable insulation over its post-injection life, and

2.    The capabilities of the molecules that are delivered to …

a.    interfere with the growth of water trees,

b.    interrupt the conversion of water trees to electrical trees, and

c.    disrupt the inception of partial discharges.

However, it is true that when using Unsustained Pressure Rejuvenation (UPR), more fluid can be delivered into the cable strands with longer soak periods.  Novinium is not dead-set against soak periods.  We employ soaking for special cases.  For example, we sometimes employ a soak period on submarine cables with constrained geometries.  A soak period, however, to compensate for a catalyst error is unforgiveable.  Soak periods compromise safety and operational efficiency and should only be utilized where technical or economic considerations preclude the use of sustained pressure rejuvenation or for unusual cases such as the aforementioned constrained geometry submarine cable.  The figure nearby provides a summary of laboratory measurements of the amount of PMDMS fluid that is supplied during a typical 60-day soak period for 1/0 AWG and No. 2 AWG cables.  Each experiment was performed in triplicate.  The amount of PMDMS provided during the soak period is about the same as the amount of fluid lost from catalytic inefficiency.  Perficio™ 011 fluid uses a patented catalyst system that enjoys a 2% catalytic inefficiency compared to the 39% inefficiency suffered by the TIP catalyst.  Therefore, Perficio fluid delivers about the same amount of active ingredient in the cable insulation without a soak as the older technology delivers with a 60-day soak period.

An even better option is to use Ultrinium™ 732 fluid, which not only uses the same state-of-the-art catalyst used by Perficio, but also includes five other ingredient types (both water reactive and not water reactive), which all increase cable life well beyond that possible with the venerable PMDMS fluid utilized in the Perficio formulation.  In future posts, I will examine each of these ingredients in more detail to shed light on how they function to extend cable life.  The table nearby will be updated to provides the links to the post for each of the five ingredient types.

In the mean time check out Cable Rejuvenation Mechanisms: An Update from the 2010 CIGRÉ Canada Conference on Power Systems.

Smarter each day,

Thermonuclear

Cole Hammond - When Experience Counts

Dealing with high voltage cables demands rigorous training and lots of experience.  Injecting those same cables requires another layer of expertise layered on top of the medium and high voltage line experience.  Novinium is staffed with experienced experts … the best in the world.  What about the case where the injection is going to occur on the cable under several hundred meters of water.  Who are you going to call?  If its fresh water you should call me – I am as at home in the water as I am on land, but salt water irritates my sensitive skin.  A girl has to look after her skin.  Now most of my human friends prefer to stay in the boat when dealing with submarine cables, but my friend Cole Hammond is as likely in the water as I am!  I am not comfortable with the whole topic of interspecies relationships, but Cole gets me wondering.

Cole is a journeyman-lineman and has been injecting cables for over a decade.  He has had his Ocean Corporation Commercial Diving Certification even longer.  If you think electricity and water don’t mix you should spend some quality time with Mr. Hammond.

The world’s most experienced and capable rejuvenation teams are at Novinium, because that is where the latest technology is practiced.  Only Novinium can supply the older unsustained pressure rejuvenation (UPR) process and the newer sustained pressure rejuvenation (SPR) process.  Only Novinium can supply older fluid injection technologies and the most modern formulations that are tailored to the unique needs of each circuit.  Cole and his colleagues are the most experienced team to deliver the full range of injection technologies in the world.

Cole used to work for the other rejuvenation supplier, so I asked him what the big differences he perceived between the two approaches.  Cole said, “First – if all you have is a hammer, everything starts to look like a nail.  The one-size-fits-all-model I practiced at the old firm is quaint in comparison to the way I tailor the chemistry and the process to the needs of my customers.   Second, the old process was invented over two decades ago and has not changed appreciably since then.  Compare that same-old-same-old stasis to my experience here, where we are introducing new products, improved chemistry, and new injection methods at a dizzying pace.  Improvements come continuously … that makes working at Novinium much more enjoyable because I keep learning and learning.”

Experience does count,

Thermo