25. August 2011 20:47
Tanδ ex post facto
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?
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