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It’s All In The Interpretation-Outliers Count

It’s All In The Interpretation-Outliers Count. Carl Landinger Hendrix Wire & Cable. Tests In Which The Temperature Gradient And Water Penetration Act In Unison. Anaconda Wet Tests. Sample With No Water In Conductor. Conductor. Test Voltage. Direction Of Temperature Gradient.

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It’s All In The Interpretation-Outliers Count

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  1. It’s All In The Interpretation-Outliers Count Carl Landinger Hendrix Wire & Cable

  2. Tests In Which The Temperature Gradient And Water Penetration Act In Unison

  3. Anaconda Wet Tests Sample With No Water In Conductor Conductor Test Voltage Direction Of Temperature Gradient Constant Heat Source To Heat Water In Tank Direction Of Water Penetration

  4. ALCOA ACLT W/Water In Cdr.EPRI Accelerated Cable Aging Test Conductor Test Voltage Water Filled Tank Sample(s) Direction Of Temp. Gradient Grd. To Neutrals Heat Conductor With Current Maintain Water In Conductor Temperature Cycling, 8 hr on—16 hr off Direction Of Water Penetration

  5. AEIC Water Tree Test W/Water In Cdr.Pirelli Water Tree Test W/Water In Cdr. Conductor Current Transformer Sample Test Voltage Grd. To Sample Is in Water Filled Duct Neut. Heat Conductor With Load Current Maintain Water In Conductor Current/Temperature Cycling Temperature Gradient Water Penetration

  6. Tests In Which The Temperature Gradient And Direction Of Water Penetration Are Opposing

  7. ALCOA ACLT No/Water In Cdr. Conductor Test Voltage Water Filled Tank Sample(s) Direction Of Temp. Gradient Grd. To Neutrals Heat Conductor With Current No Water In Conductor Temperature Cycling, 8 hr on—16 hr off Direction Of Water Penetration

  8. Pirelli Water Tree Test No/Water In Cdr.(Filled Strand) Conductor Current Transformer Sample Test Voltage Grd. To Sample Is in Water Filled Duct Neut. Heat Conductor With Load Current No Water In Conductor Current/Temperature Cycling Temperature Gradient Water Penetration

  9. In Service Cables With Water In The Conductor Water penetration and temperature gradient work in unison. Conductor Direction of temperature gradient Direction of water penetration

  10. In Service Cables With No Water In The Conductor Water penetration and temperature gradient are opposed. Conductor Direction of temperature gradient Direction of water penetration

  11. Wet Test Results On XLPE Insulated Cables, Time To Failure Or % Loss Of Dielectric Strength No Water In Conductor (Pirelli) (ALCOA) Time To Failure Or Dielectric Strength Water In Conductor (ALCOA, EPRI) Temperature Gradient

  12. Wet Test Results On EPR Insulated Cables, Time To Failure Or % Loss Of Dielectric Strength No Water In Conductor (Pirelli) Time To Failure Or Dielectric Strength Water In Conductor (EPRI) Reverse Gradient, No Water In Conductor (Anaconda) Temperature Gradient

  13. Wet Tests Comparing EPR & XLPE Insulated Cables, Time To Failure Or % Loss Of Dielectric Strength EPR, Water In Conductor (EPRI) No Water In Conductor (Pirelli) Time To Failure Or Dielectric Strength XLP, No Water In Conductor (Pirelli, ALCOA)* XLP, Water In Conductor (EPRI, ALCOA, Pirelli) Temperature Gradient *Anticipated

  14. Trying To Estimate Service Life The Unwelcome Outlier -Which Data Point Most Interests You? x x Best Fit Data Plot x x Accelerating Factor x x x More x Outlier x Time To Failure Of Samples Under Test Longer

  15. Variation In AC Breakdown With Cable Length, EPRI Proj. IEEE/PES T&D Paper 89 TD 365-8 Representation Which Point Catches Your Eye? AC Breakdown Volts/Mil “0” Ft. 400 Samples 10,800 Ft. (Broken Down With AC Voltage)

  16. Some Necessary Observations • Laboratory aging tests are generally conducted on • “feet” of cable while service failure rates are quoted • in failures “per 100 miles per year” • 2. In order for aging tests on “short samples” to give • any indication of service life the total cable • represented by the samples must be sufficiently • homogeneous to be capable of being described • (without exception) by normal statistical means • (in control). The presence of even an occasional • outlier belies this possibility.

  17. OPINIONS • Wet tests in which the temperature gradient and • water penetration work in unison are suitable to • compare a modified material to a known material • of similar composition with respect to degradation • due to moisture; HMWPE vs HMWPE, XLPE vs • XLPE and hopefully EPR vs EPR • 2. Wet tests in which the temperature gradient and • water penetration work in unison are not a • promising means to predict service life of modern • cables; dry conductor, jacketed cables

  18. OPINIONS 3. Today's aging tests (short lengths of sample) will not yield useful information on service failure rate of modern cables (unless material change, process problems or defects are present in sufficient quantity to yield poor results). 4. Future life test development will have to test complete designs in a manner duplicating service conditions and in sufficient length to include scattered “defects” and “worst case” operating conditions.

  19. Opinions 5. Modern materials which are relatively long lived in aging tests when compared with past materials having a poor service record will most likely have their service life determined by outliers and field events not included in the tests.

  20. Partial List Of References • ICC-IEEE Meeting Minutes, April 1984, • Appendix V-F-5 (Pirelli) • 2. IEEE Trans. Power Del. April 88, ppgs. • 434-439 (ALCOA) • 3. IEEE Trans. E.I. Dec. 81, ppgs 521- 527 • (Anaconda) • 4. I was there! (Anaconda, ALCOA, CPI/ • EPRI). Just couldn’t keep a job.

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