Third Party

Dear Alert Amphibian-

Can you provide third party data demonstrating that cable injection will extend the life cycle of underground cables? My colleagues and I are preparing for a rate filing with the OEB and we are looking for some firepower, facts and figures to bolster our case for additional cable injection monies for 2014 and beyond.

Seeking help,

Organizing in Ontario

Dear Organized-

I can think of four “flavors” of third-party data.

Flavor 1

Flavor 1 includes data gathered by third parties at the behest of a firm engaged in rejuvenation. The third party is independent, and is generally working for the technology supplier. There is an ample supply of this type of data, spanning over two-and-a-half decades. As an example of this type of data, consider Figure 3 of the paper published by my colleagues at the IEEE International Symposium on Electrical Insulation in September 2004…

New Developments in Solid Dielectric Life Extension Technology 

Figure 3 shows the substantial improvement in AC break-down performance seven days after injection at Cable Technology Laboratories. There is an abundance similar Flavor 1 third-party data. A compilation of that data can be found in the bibliography presented at the NETA Powertest Electrical Conference on March 17, 2008.

History and Status of Silicone Injection Technology with Bibliography

This paper provides 50 references including flavors 1, 2, and 3 of third-party data.

Flavor 2

The second flavor of third-party data are results reported by end-users. There have been several North American utilities that have reported their post-rejuvenation reliability over multiyear periods. The IEEE’s Insulated Conductor’s Committee (ICC) Discussion Group C30 is compiling several of these case studies as part of its efforts to craft a Guide entitled, “Extending the Life of Power Cables in the Field.” One exemplary data set was published by Northeast Utilities at the spring 2008 ICC. I have attached an excerpt of the ICC meeting minutes below. Over a nine year period from 1999 to 2007, the failure rate of the post-rejuvenated cable was 0.7% and the failure rate of the non-rejuvenated cable was 12%. Novinium’s failure rate is about half of the failure rate enjoyed with this older technology – see flavor 3.

R.Vencus. Cable Injection Program CL-P 2008.pdf (8.13 kb)

Flavor 3

The third flavor of third-party data is the overall failure rate of rejuvenated cables. Circuit owners have an incentive to report their post-injection reliability issues as they get cash for doing so! Novinium transparently publishes these statistics at …

http://www.novinium.com/Lessons.aspx

Novinium’s post rejuvenation failure rate is less than that of new cable! Check out my March 23, 2012 post, “Better Than New” to learn more.

Flavor 4

The fourth flavor of third-party data would be a Coke vs. Pepsi, side-by-side “taste test” of different rejuvenation technologies funded by electrical circuit owners and conducted by a third-party laboratory. There is good news, there is bad news, and some new that falls between good and bad. The good news is such a test was arranged by NEETRAC (National Electric Energy Testing, Research & Applications Center) sponsoring firms including: AEP, BG&E, ConEd, Oncor, FPL, Exelon, Southern Company, PEPCO, Southwire, and Snohomish Public Utility District. The bad news is that only Coke showed up for the taste test! The other technology supplier participated in the experimental design, but withdrew just as the testing was to commence citing, “Business and commercial reasons.” I will leave it for your contemplation why the other guys would not want to participate in a side-by-side test. The test proceeded with Novinium only. The news that is not bad, but not ideal is that even though the test was completed about two years ago, NEETRAC has not yet published the results in anything other than draft form. An excerpt of the draft NEETRAC report provides the bottom line of the testing:

“ … the stress at which the rejuvenated cables fail is higher than for the non rejuvenated cables: 26 kV/mm and 16 kV/mm, respectively. These stresses are taken at the 50^th percentile (median). Moreover, it would appear that the [Novinium] rejuvenated cables have a threshold for failure at 4.5 kV/mm whereas there is no threshold for the Non Rejuvenated cables."

The reported performance advantage was measured after about 18 months of accelerated aging – well beyond the originally planned twelve-month experimental plan. The electrical stress of a typical 175 mil insulated URD cable energized at about 8kV to ground is 1.8kV/mm. The treated failure threshold is 2.5-times typical operating voltages even after extended thermal and electrical accelerated aging.

Ready for any party,

Thermonuclear Frog

Failure Causes II

In yesterday’s post, “Failure Causes I,” I provided a partial answer to an inquiry from Colorado Querier. Colorado sought to understand if rejuvenation technology was appropriate for the “many types of aging factors” from which his firm’s circuits might suffer. In yesterday’s post we dealt with circuit failures caused by connected components, rather than the cable itself. Today we will focus on cable failures.  First a disclaimer – it is often difficult to determine with 100% certainty the cause of a cable failure in field conditions. A cable failure is a destructive event that usually vaporizes its own root cause. Those who analyze field failures can examine the cable near its fault for neighboring defects. If a defect or defects are found, the examiner may infer without certainty that a similar defect may have been the root cause of the actual fault. If no substantial defects are found the root cause will surely remain unknowable.

I emphasized “substantial” in the last sentence because at a small enough scale there are always defects. Water trees grow in all medium voltage solid dielectric cables exposed to moist conditions. Unless you have hermetically sealed metal sheaths, those would be your cables! Water treeing is an oxidative process, but even where there are no water trees, oxidation of the polymer occurs, because oxygen and other oxidizing agents are ubiquitous. Free radicals facilitate oxidation and are common in nature. Cosmic radiation, radioactive decay, and other natural processes spawn free radicals around the clock. On top of those chemical processes there are mechanical strains placed on the cable by thermal cycling driven by load cycling.  Such thermal cycling creates micro-voids in the middle radius of the insulation driven by the “Molecular Thermodynamics of Water in Direct-Buried Power Cables.” Click here to view the paper by the same name from IEEE Electrical Insulation Magazine (Nov/Dec 2006). The collection of voids formed this way are referred to as a halo.  I provide an illustration of a halo and water tree nearby.

What are the primary causes of failure and how is each addressed or not addressed by rejuvenation?

In the frogograph nearby, I show you a subset of field reliability data (Editors note: I have come to call this kind of data – “real, real world!”) gathered by Dr. Steennis of KEMA. The simple logarithmic equation explains 78% of the relationship between maximum water tree length, expressed as a percentage of the insulation thickness and reliability expressed as AC breakdown strength.  AC breakdown strength is not a perfect surrogate for cable reliability, but it’s a pretty good one!  Lightning bolts appear next to each cable sample that failed in service. Water tree length is the single best predictor of reliability. In the same work, Dr. Steennis and his colleagues demonstrated that the laboratory failure of the field aged cables always occurred at the longest water tree, just as a chain fails at its weakest link.

Well over three-quarters of solid dielectric cable failures are caused by water trees. Rejuvenation technology was originally designed to address water tree degradation specifically. In fact, rejuvenation has a proven track record of treating the biggest and ugliest water trees on the planet.  Click here, to check out my October 5, 2011 post, “Water Trees – Too Big to Fail?” In my third post of this series we will examine the other less important root causes of cable failure and consider whether or not those root causes can or cannot be addressed by the application of rejuvenation technology.

Master of Reliability,

T. Bull Frog