The Group C18D met on Tuesday, May 8 at 10:15 a.m. to noon with 35 members and guests.

The Chairman mentioned that the vice-chairman, Rob Schlesinger, was not able to attend due to a conflict with another meeting. Fred Koch kindly agreed to take the minutes.

There were two presentations:

Fred Koch, Power Services & Equipment, Inc., presented data showing the results of VLF field tests conducted by a Midwestern US utility. The information summarized the results for testing on 440 cable tests and is included in Appendix C-10. The tests were all 15 minute tests and there was an approximate 78% survivor rate for the cables tested. It is believed there were no failures on tested cables up to approximately 1-1/2 years after the tests. The data does seem to indicate that a longer test would be valuable since there were a number of failures in the last minute of test.

There were several questions looking for further details on the data, but no further data was available.

Nigel Hampton, NEETRAC, presented a very interesting discussion, “VLF Diagnostics”, which included data being both developed and analyzed at NEETRAC, see Appendix C-11. His statistical analysis of the data seems to indicate the following:

• The relative number of failures during testing are independent of the type of VLF wave form used (sine vs. trapezoidal).

• The number of failures that occur during the test are higher at higher voltage stresses.

• The failures that occur on tested cables subsequent to the test appear to be of similar magnitude regardless of the type of wave used (sine vs. trapezoidal) and the test voltage level (2Uo vs. 3Uo).

• The cables tested for 30 minutes appear to have significantly greater longevity than those tested for 15 minutes, i.e. the time to reach 5% failure rate on the tested cables is approximately 550 days for 30 minute tests and 140 days for 15 minute tests.

Frank Petzold (SEBA KMT) asked why some tan delta data had been included. Tan delta is a diagnostic and thereby opened a discussion on non-destructive testing while the 400.2 is a withstand standard and is considered destructive.

Nigel responded the tan delta data was included to show that tan delta may be an indicator of where to go with the VLF test – time length and voltage level. IEEE 400 – 2001 will be included into the revised IEEE 400.2 when both documents are revised in the coming year.

Roland Watkins (Consultant) stated that we all believe that the newer extruded cables are far superior to the early cable and asked if Nigel could prove that from the data available. Nigel stated that he could not because the data is not available. Those doing testing at present are testing the older cables (those giving problems) rather than newer vintage cables.

Ben Lanz (IMCORP) stated that he believes some companies are using the test levels being discussed as a proof test (acceptance) for new installations. Nigel said he made a conscious effort to exclude new installation tests from the data wherever he could identify it as such. His data was restricted to maintenance tests.

Craig Goodwin (HV Diagnostics) asked how the types of cable systems were discerned on the Exelon test data.

Nigel said that ComEd engineers reviewed the fault codes in their data to determine to the best of their ability the type cable system (PILC vs. Extruded) and then NEETRAC tried to pull all the data together.

Ben Lanz commented that data on acceptance tests would probably look somewhat different.

John Densley then reviewed and discussed the “points for discussion” that were listed in the agenda.

Bill Thue and several others commented on including data on non-tested cables in order to be able to make a statement on the value of testing. There seemed to be agreement that this would be good data if it can be obtained.

Vern Buchholz (Consultant) asked Nigel if he thought the curve (for failures) would be steeper on cable not VLF tested if they were looked at from a point in time and compared to the curves showing cable failures after VLF testing. Nigel stated that the little data he has seems to look like the non tested cables are going up a steeper slope than those tested.)

John Densley then opened the subject of including a “Smart Withstand Test” in the revision of 400.2 to aid the users in making better use of the technology, see Appendix C–12. The possibilities shown included a variety of criteria that might be used as an indicator of how to continue the withstand test rather than simply using time alone.  Appendix C–12 lists more information than that presented at the meeting.

There was general agreement that a “smart” test would have a lot of value and should be pursued. Bill Thue mentioned that it may be more correct to include it as an addendum to the 400.2 standard – perhaps a 400.2.1.

Kent Brown (TVA) mentioned that he had found monitoring the Tan Delta levels during VLF testing to be an indicator and he graciously volunteered to present a discussion on stability of tan delta measurements during VLF testing at the next meeting.

Larry Bobb (Potomac Electric), who could not make his presentation at the meeting due to an incompatibility between his software and the computer, will also make his presentation at the next meeting.

Attendance: The Discussion Group met on Wednesday, November 7, 2007 at 8:00 a.m. with the following 40 members and guests in attendance:

Participant IEEE Number Affiliation

Bardwell, J. Black & Veatch

Baur, M. Baur

Bernstein, B. BSB Consulting

Bromley, J. Manitoba Hydro

Brown, K. TVA

Buchholz, V. Consultant

Buckweitz, M. ConEd

Campbell, T. ConEd

Chen, W. SMUD

Chumley, G. Prysmian

Cormar, B. Hydro One

Cooper, J. PDC

Coté, J. Hydro Quebec

Cunningham, R. Seattle City Light

Densley, J. ArborLec Solutions

DiGuglielmo, F. PSE&G

Drapeau, J.-F. Hydro Quebec IREQ

Grodzinski, C. EHV Power

Gulski, E. TU Delft

Haas, R. Pasadena W&P

Hampton, N. NEETRAC

Katz, C. CTL

Koch, F. PS & E

Landers, G. Von Corpn

Lanz, B. IMCORP

Lindler, C. Prysmian

Liu, C. AEP

Motallebi, H. LADWP

Oetjen, H. HDW Electronics

Pasha, M. United Illuminating

Patterson, R. NETA

Perkel, J. Georgia Tech/NEETRAC

Petzold, F. SEBA KMT

Rampley, G. Salt River Project

Schlesinger Consultant

Tirinzoni, P. North East Utilities

Von Herrmann, M. Von Corpn.

Wharton, P. Horizontal Wind Energy

Wiebe, R. First Energy

Zhao, T. EPRI

Minutes: The IEEE policy regarding copyright and patent responsibilities was discussed.

Presentations were made by Henning Oetjen and Nigel Hampton.

The presentation by Oetjen addressed the mechanisms of water trees, the effect of the voltage wave shape on the growth rate of electrical trees, the distribution of the times to failure during a withstand test, the time to in-service failure after testing, and the possibility of using leakage current to monitor test duration. The slides presented are shown in Appendix C-14.

The presentation by Hampton, Perkel, Altamirano, and Hernandez, presented by Hampton, reported on the VLF test data collected as part of their CDFI project. Issues covered included the temporal and voltage variations of tan delta and tan delta (1.5Uo – 0.5Uo) of cable circuits, and the effects of test voltage and duration on the number of circuits surviving the test and the times to first failure in service after testing. As the tan delta values of the cable circuits tended to fall on one curve, an attempt was made to assess the condition of the cable circuits based on this curve. The slides presented are shown in Appendix C-15.

A point raised in the discussion of the presentation was that the loss currents in the terminations and splices contribute to that of the cable in the measured value of tan delta. The influence of the accessories could dominate the measured tan delta.

It was decided to begin the revision of IEEE 400.2 by assigning responsibility of the different sections to regular attendees of the discussion group. The following volunteered to review the allotted sections and revise if necessary:

Section 2: Normative References – Nigel Hampton.

Section 3: Definitions and acronyms – John Densley

Section 4: Safety – Fred Koch and Rob Schlesinger

Section 5: VLF Testing – John Densley and Kent Brown

Section 5.1: General VLF Testing – Nigel Hampton, Henning Oetjen, and Rob Cunningham

Section 5.2: VLF Testing with Cosine-Rectangular/Bipolar Pulse Waveform – Henning Oetjen

Section 5.3: VLF Testing with Sinusoidal Waveform – Martin Baur and Rob Schlesinger

Section 5.4: VLF Testing with Regulated Positive and Negative DC Voltages – omit

Section 5.5: Dissipation “Factor/Differential Dissipation Factor/Leak Current/harmonic Loss Current Tests with VLF Sinusoidal Waveform – Nigel Hampton, Henning Oetjen, Craig Goodwin, and Kent Brown

Section 5.6: partial Discharge Tests with VLF Sinusoidal Waveform – John Densley

Section 5.7: Dielectric Spectroscopy with VLF sinusoidal Waveform – Frank Petzold

Section 6: Conclusions – John Densley

The revisions should be sent by e-mail to the Chair (j.densley@ieee.org) and the review group by February 15, 2008, so that their comments can be discussed at the Spring meeting.

The review group is Mark Walton, Ralph Patterson, Carlos Katz, Kent Brown, Jim Bromley, Craig Goodwin, Gerry

 Landers, Nigel Hampton, Rob Schlesinger, and John Densley.