by Thermo
12. September 2011 20:53
Concordance of IEEE 400.2™ & Warranty
Dear Astute Amphibian,
The definition of “Discouraged Diagnostic Testing” found in your warranty language does not seem to allow VLF testing in accordance with IEEE 400.2™.* In the unlikely event that a rejuvenated cable fails in service, we would want to repair the fault and test the cable with one of the approaches outlined in IEEE 400.2. Is there some reason we should not, or cannot, test using IEEE 400.2 protocols?
Signed,
Power Creek
Dear Creek-
Inscribed in stone on the Novinium warranty are the following words:
Discouraged Cable Diagnostic Testing includes any exposure of the cable Segment to (1) a voltage greater than 50 volts at any frequency below 50 Hz or above 60 Hz, (2) any exposure of the cable Segment to voltages at any frequency above the rated voltage of the cable, (3) any cable testing with duration greater than 2 minutes, or (4) any DC cable testing at a voltage greater than 1 kV.
Each word was chosen very carefully and the keyword to address your question is the first. The first word is “Discouraged,” not “Prohibited.” IEEE 400.2* points out in several places, such as the bottom of page 5, that …
“… when the cable system insulation is in an advanced condition of degradation, the diagnostic tests can cause breakdown before the test can be terminated.”
Most cables that are rejuvenated are in an “advanced condition of degradation.” In fact, most solid dielectric cable of vintages manufactured prior to 1985 is in an “advanced condition of degradation.” The diagnostic tests described by IEEE 400.2 may cause a cable to fail that otherwise would have provided reliable service. Novinium’s masters of reliability discourage activity that may exacerbate incipient reliability issues, but we do not presume to prohibit. In the case, where such testing is performed on rejuvenated and reliable cable the warranty is suspended for 120 days, not forever invalidated.
Furthermore, in your particular scenario the warranty situation is moot. When a Novinium rehabilitated cable fails, Novinium’s standard warranty provides money-back to the circuit owner. After Novinium disburses the refund, there is no further warranty obligation on that section of cable. The circuit owner is unencumbered from using any of a plethora of available destructive diagnostics.
Astutely yours,
Thermo
*IEEE 400.2™ is the IEEE Guide for Field Testing of Shielded Power Cable Systems Using Very Low Frequency (VLF). IEEE 400.2 is a trademark of the IEEE.
by Thermo
25. August 2011 20:47
Tanδ ex post facto
Dearest Amphibian,
I have sent you some before-and-after diagnostic data (0.1Hz tan-delta) on two cables treated with Novinium® Ultrinium™ 732 fluid? The results are extraordinarily positive. What say you?
Greater Chicago
Dear Greater-
The data you provided is reproduced in the chart nearby. A few of my historical postings provide evidence that I am not a big fan of diagnostics. For example check out the postings below ...
2010-11-12 Diagnostic Testing – Should I do it?
2010-12-12 Electrical Treeing and the Principle of Parsimony
2011-05-11 Middle East Query – Diagnostic Testing Timing
2011-05-19 On-line Diagnostic Testing
Check out the before-and-after dielectric spectroscopy data presented in another post when I addressed tan delta measurements specifically at …
2010-09-10 Cable Rejuvenation Impact on Loss Factor (tan-Delta)
The data from the University of Connecticut’s Electrical Insulation Research Center (EIRC) in that post leaves no doubt that rejuvenation has an impact on tan delta measurements, but it creates considerable doubt as to the meaning of that impact. It is also true that there can be no doubt that rejuvenation with Novinium fluid technology provides a reliable post-injection life extension – over 99.6% of all treated cables are providing failure-free performance.
It is tempting, whether human or amphibian, to embrace data when it reinforces what you already know. As a disciplined scientist, I, however, am able to resist that temptation. The 17 month improvement demonstrated by the Illinois Cable 1 and Cable 2 data suffers at least two shortcomings. First, there were precisely two cables measured two times about 17 months apart. That is not a statistically significant data set. Second, without following the tan-delta over time, it is not possible to correlate the “improvement” with a reliability-metric like AC breakdown performance, which has been measured and modeled extensively. We can rectify these two issues with a more comprehensive analysis that includes more cables and more frequent periodic re-testing. Such a program is in the works with Greater and we will report on the results as the data becomes available. The testing itself carries risks for the cables to be tested. Knowledge is not free and you can’t make an omelet without breaking some eggs.
Interested, but skeptical,
T. B. Frog
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