Dielectric II

In Dielectric I, I provided the first part of a four-part answer to a query from Alabama – the summary question: To what extent does the introduction of injection equipment into energized devices impact the safe operation of medium voltage circuits? We learned that there are great differences in the extent of this risk depending upon the injection paradigm employed. In fact there are three injection paradigms and at Novinium we use only the safest processes. With Novinium’s patented SPR (sustained pressure rejuvenation) there is zero additional risk. With Novinium’s iUPR (improved unsustained pressure rejuvenation) process the risk is many times less than the legacy approach used by others. The legacy paradigm is called UPR (unsustained pressure rejuvenation). In this post I provide data to show why the feed end of an iUPR injection is not a safety issue – unfortunately the same conclusion is not true for the legacy UPR process.

In the illustration nearby I am standing next to iUPR injection equipment. From left to right are …

A CO₂ cylinder enclosed in a PVC bag provides energy to urge fluid into the cable strands.  A polyethylene CO₂ supply tube provides about 20 psig of pressure to the predominantly plastic feed tank. At least three feet of polyethylene fluid supply tube with a wall thickness of 100 mils delivers fluid to an injection adapter and a mated injection elbow. In another case not illustrated, the fluid might be supplied to a live-front injection adapter. Whether dead-front or live-front, the fluid comes in direct contact with an energized conductor. The fluid is a dielectric, and with Novinium’s improved unsustained pressure rejuvenation process, the flow is one way – toward the termination. This one-way flow provides assurance that there is no fluid contamination from backward flow as suffered by legacy approaches. At Cable Technology Labs (CTL) the leakage current in a column of Ultrinium™ 732/40 fluid was measured between two electrodes at 15, 25, and 35 kV. The leakage current was steady at about 0.03 mA, 0.04 mA, and 0.05 mA for 15, 25, and 35 kV respectively from 14 feet of electrode separation down to less than 1 foot.

With the Novinium iUPR process there are no ground electrodes ever in direct contact with the fluid. The fluid flows though several feet of PE tubing with a wall thickness of 100 mils. The AC breakdown strength of the PE is at least 800 volts/mil and hence the AC breakdown strength of the tubing is greater than 80 kV. The fluid flows from a polypropylene/acetal tank with even thicker walls than the tubing. The closest ground plane is typically the concrete or earth on which the feed tank rests. Novinium has deployed these iUPR systems thousands and thousands of times and there have been zero issues. We wrap the CO₂ cylinder in a PVC bag to prevent accidental contact with exposed secondary voltages.

In my third post in the series, Dielectric III, I will discuss the design issues of the vacuum tank designed for iUPR and the features that make iUPR the second safest injection approach. Finally, in Dielectric IV, I will address the equipment separation issues Alabama raises in his questions, 6 through 8.

Dielectrically delighted,

T. B. Frog

Dielectric I

Dear Wisest Webbed one,

I am working on my comments/concerns for the Safety Section for the C30 Draft Guide [Editors note: C30 is a group within the IEEE/PES/ICC working towards the writing of a “Draft Guide for Rehabilitation and Rejuvenation of Extruded Dielectric Cable Rated 2.5 kV through 46 kV.” While that Draft is being crafted, interested readers may wish to review a Novinium published early version undertaken at the behest of the group’s chair, which is available at www.novinium.com/Standards.aspx.], and have a few questions. Just because the equipment is all or mostly plastic materials, these questions still need to be explored and discussed.

1. What is the insulation rating of the fluid(s) that you use for injecting?
2. What is the insulation rating of the hose(s) you use from your canisters to the injection point?
3. What is the insulation rating of the canisters themselves?
4. What is the insulation rating for the combination elbow/canister?
5. Do you have the test data for these pieces of equipment? Will you share the test data with the group?
6. Have you looked at the electrical separation distance from your canisters to the cover or live bushing?
7. Have you looked at the electrical separation distance from your canisters to ground wires in the equipment?
8. Have you looked at the electrical separation distances from your canister connected to one phase and to the other phases in a three phase installation?

Your froguidance would be appreciated.

Alabama detailed draft

Dear Alabama-

I don’t know about you, but the fact that the first three letters in dielectric spell “die” makes me want to take extra measure to assure the safety of all who use dielectric enhancement technology. The heart of your eight questions can be summarized thusly: To what extent does the introduction of injection equipment into energized devices impact the safe operation of medium voltage circuits? Before I answer that question generally and some of your more specific questions, it is important to recognize that there are three distinct methods of dielectric enhancement fluid injection and two conductor realms in which those methods are deployed. Ordered from oldest to most advanced, the three methods are:

    UPR ♦ Unsustained Pressure Rejuvenation,

    iUPR ♦ improved Unsustained Pressure Rejuvenation, and

    SPR ♦ Sustained Pressure Rejuvenation.

To learn more about the details of these rejuvenation methods, check out my June 18, 2010 post titled “How to Inject.” Novinium is synonymous with safety, so we use the two most advanced processes almost exclusively. In the very unusual cases where Novinium leaves injection devices attached to energized devices for more than a couple of days, equipment designed specifically for that case is deployed. Because it is a rare case, I refer interested readers to my April 15, 2001 post, “Soaking II: Safety First” for more details.

In this series of posts, I focus on the cases most important to circuit owners. In the table nearby the implementation of the three injection methods are compared for the two conductor cases, namely small conductor and large conductor. Small conductors include stranded conductors, generally with 19 or fewer strands. Note that for large conductors, cables are injected de-energized whichever injection method is utilized, and hence your questions are moot for these large conductors. Further, SPR is applied over 99% of the time to deenergized cables, and hence the questions are again largely moot. The only firm in the world that can deliver iUPR and SPR is Novinium, because we own the intellectual property on the methods and chemistry that make those processes possible. For most injection work we undertake, we operate in the green … my favorite color.

When we do inject into energized devices we mitigate the risks about which you are inquiring by limiting the period that injection equipment is connected to energized components. In the red portion of the table, older technology requires extensive soak periods spanning several months. At first glance you might assume that reducing the period of time by sixty-fold would reduce the exposure to the risk by sixty-fold, but you would be underestimating the impact. In the iUPR process, fluid flows in only one direction. A feed bottle with a positive pressure, typically about 20 psig, is attached to one cable end and a vacuum bottle with a negative pressure of around -10 psig is attached to the other cable end. Fluid flows from high to low pressure. Both the feed tank and the vacuum tank are removed concurrently. Thus on the feed side, fluid with a high dielectric strength flows through tubing made of a high dielectric polymer and there is a negligible probability of substantive current flow. I’ll provide some data in my second post, Dielectric II.  With iUPR the only substantive design issue is on the vacuum or outlet side, there is no way to be certain what will come out of the outlet, so we have to assume that it will be water. In practice, water seldom comes out of 7-strand or 19-strand cables (To learn why, click here.), but from a design perspective this is the worst-case assumption.

UPR has the same worst-case on the outlet end, but it also suffers from a more insidious issue on the inlet end. I examined this issue in some detail in my April 15, 2011 post, “Soaking II: Safety First.” You should read that post, but in summary, UPR suffers a risk that conductive contaminants will render the feed fluid conductive. The worst-case assumption on the inlet side is about the same as the on the vacuum side, but the feed is connected for 60 days or more. This risk is recognized by the practitioners of UPR, because they explain the risk and a potential solution to mitigate the risk in U.S. Patent 7,704,087 of April 27, 2010. Amazingly after exposing the risk those practitioners have not implemented their mitigation strategy. I usually speak only of technical matters, but you don’t have to have a law degree to recognize that if you know about a safety problem, but do nothing to mitigate the issue – your liability undoubtedly increases. Risk managers should take this knowledge into account as they make their choice between the various injection processes. If your firm believes in safety as the most important criteria, don’t utilize UPR.

In my next post (Dielectric II), I will provide some data to show why the feed end of an iUPR injection is not a safety issue. In my third post in the series (Dielectric III), I will discuss the design issues of the vacuum tank designed for iUPR and the features that make iUPR the second safest injection approach. Finally, in Dielectric IV, I will address the equipment separation issues you raise in your questions, 6 through 8. For a thorough description of all of the rejuvenation dimensions of safety check out the 89-page treatise, “A Comparison of Rejuvenation Hazards & Compatibility.”

Practicing safe rejuvenation,

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