Monday, March 22, 2010 from 3:30 to 5:30 p.m.

Agenda Items:

1. Go through Comments on Draft #7 of revised document
2. Finalize tan delta and differential tan delta values
3. Set times for issue of next draft and when comments due

The attendance was 25 members and 31 guests.

The following Working group members attended the meeting: New members are indicated with a “ * “.

Densley, John *Hayden, Tim

Abdolall, Kal Koch, Fred

Baur, Martin Lanz, Ben

Brown, Kent *Matthew, Roy

Côé Jacques Oetjen, Henning

*De Vries, Frank Olson, Bruce

Drapeau, Jean-Francois Patterson, Ralph

Fenger, Mark Petzold, Frank

Goodwin, Craig Vencus, Richard

*Graham, Steve Walton, Mark

Gulski, Ed Zenger, Walter

Hampton, Nigel Zhao, Dawn

Hans, John

Minutes

John Densley, Chair, called the meeting to order and requested volunteers for a new vice-chair since Rob Schlesinger had recently resigned.

The IEEE-SA policy slides concerning patent issues had been presented at the Opening Session. The Chair provided an opportunity for participants to identify patent claims, patent application claims, or patent application claims of which any participant was personally aware and that may be essential for the use of this standard. No issues were identified at this time.

Approximately 200 comments were received on draft #7 and most have been incorporated into the preliminary draft 8. The main focus of the meeting was to discuss the revision of test voltage values in Table 5, to explain the rationale for the revisions, and to present the addition of condition assessment tables showing tan delta, differential tan delta and mean tan delta values for three insulation systems.

The scope has changed since 69 kV cables are now included. Rather than call it a guide for “high Voltage” cables, we should keep “medium” in the title and it was recommended  to modify the scope to say “medium and high voltage cables through 69 kV”.

There were comments that IEC uses “high voltage” to describe cables at 69 kV and much higher voltages. The general feeling was that the revised wording will not confuse users of this guide.

John Densley explained that the values in the tables were derived from the work at NEETRAC. The columns are arranged from left to right in the order of what appeared to be most important from the NEETRAC work, i.e., the tan delta stability over time appeared most important, followed by the differential tan delta and the absolute value of  tan delta. It was recommended and approved to add a note explaining why the columns are arranged in the order they were from left to right to help the users understand their relative importance.

John showed the differences between the values in these tables and values provided by  Martin Baur, who had summarized international values. While the tables just added to preliminary draft 8 are based on data from the US, it is recognized that there are data from throughout the world often with quite different values as shown by the tables  submitted by Martin. Since it is to be an international standard, Martin Baur will attempt to get the source data from which his tables were developed and an attempt made to “harmonize” this data with the US figures. If the source data cannot be obtained or the different values cannot be explained they may be included in an annex.

Nigel Hampton explained that values in the tables were developed from data resulting from approximately 3700 tests over a five year period. Nigel explained the rationale behind the values were based on the 80/20 rule. Nigel showed graphs (Weibull plots) of the data he developed from the differential tan delta results for each of the three cable types. He chose the values for further study as those in the 80% to 95% range and values for action required as those in the 95% to 100% range.

Jean-Francois Drapeau questioned the values listed for paper cable. Nigel explained these were the exception as compared to the solid dielectrics cables. With the paper cables the lower part of the graph goes negative and the “double sided approach” was used where the top and bottom 10% were chosen to comprise the 20% for further study or action required.

Jacques Coté asked if the methodology would be included. The methodology will be explained either as an annex in the guide or possibly as an IEEE Transactions paper  and referenced in the guide. The object is to establish a transparent methodology users can understand and also use as a guide in the future collection and analysis of data.

Martin Baur and Walt Zenger suggested a fixed test time is needed and if not perhaps a range of test times. John said he will look at it but draft #8 will be more specific with the test times.

Kal Abdolall asked if the environment was accounted for in the test results (wet/dry – summer/winter). Nigel said that it is not separated based on environment.

Henning Oetjen asked if the belted cables were tested phase to phase or phase to ground. Nigel answered that they were tested phase to ground.

There was a question on whether or not these values were compared to 60 Hz values.  Nigel stated that they were not. Testing at 60 Hz is rather difficult. That said there have been some small studies at 60 Hz that show the ranking appears to be similar though the values are different.

Kent Brown said he is not sure if lumping all EPR type cables together is correct for the condition assessment. It may have more to do with the formulation than is apparent at this point. This can be looked at as additional data are collected and analyzed.

John mentioned that Europe has separated the data for XLPE and TR-XLPE but that

Nigel believes they can be included in a single table and has done so in the tables he presented.

Walt Zenger pointed out there appears to be a typo with the values using 10-3. John and Nigel will check these values.

The consensus of the discussion appeared to be a general agreement with the methodology developed.

Nigel pointed out that he is happy to accept all data available.

John explained the minor changes to the voltage values in Table 5 were to add consistency. He showed the graphs of the previous values and how minor changes resulted in those now in Table 5. The resulting straight line graph seems to be more sensible and it also allows for the derived equation to be used to arrive at values for a cable system not listed in the table. John also showed a graph of preliminary Draft 8 values vs. those shown in IEC 60840 and they are similar.

There was agreement to keep the new values. However, these values have a commercial impact in that some test sets now on the market may miss the values by 1 or 2 kV (<5%) since they were aimed at the older tables. Also, customers have been using these sets and the values in the older tables. After a discussion it was decided to add a note recognizing that though some test sets fall just short of these values “expert” opinion is that they can be used without adversely affecting the results or validity of the test.

Table 3

After a discussion of Table 3, it was decided to eliminate it from the guide.

Table 2

Table 4

There was a short discussion of the addition of the Monitored Withstand test to Table 4.

Kent Brown expressed concern that an average user may have difficulty interpreting where to start with the various options offered in the guide.

After discussion, John explained that this guide is actually somewhat more simplified than the previous one. It may appear very complicated in draft form since it shows all the old and new items in one document.

John will put out two new versions (Draft #8) prior to the next meeting. One will show all the mark-ups and the other will be in “final” form which will be much shorter and should be simpler to read.

Minutes prepared from notes taken by Fred Koch.

Tuesday, October 19, 2010 from 3:30 to 5:30 PM.

Agenda Items:

There will be no formal presentations.  The only item on the agenda will be to go over the comments received on Draft 9 of the Guide.  I have already received comments from some of you.  Although the original deadline was today (10/8/10), please send your comments as soon as you can so that I (John Densley) can tabulate them for the meeting
 

Attendance

The attendance was 19 members and 8 guests.

The following WG members attended the meeting: WG members are indicated with an asterisk.

*Densley, John *Petzold, Frank

*Hayden, Tim *Tarampi, Dexter

*Brown, Kent *Vencus, Richard

*Côté, Jacques *von Herrmann, Martin

*De Vries, Frank *Zenger, Walter

*Drapeau, Jean-Francois Al-Sibai, Mohammed Eyed

*Fenger, Mark DePriest, Douglas S.

*Goodwin, Craig Levine, Jody

*Graham, Steve Lindler, Carroll

*Gulski, Ed Lindsay, David

*Lanz, Ben Norris, Aaron

*Olson, Bruce Prier, Ken

* Orton, Harry Smith 111, John T.

*Patterson, Ralph

John Densley, Chair, called the meeting to order and introduced Tim Hayden (National Grid) who has agreed to be the Vice-Chair.

The IEEE-SA policy slides concerning patent issues had been presented at the Opening Session. The WG Chair provided an opportunity for participants to identify patent claims, patent application claims, or patent application claims of which the participant is personally aware and that may be essential for the use of this standard. No patent claims, patent application claims, or holders of patent claims or patent application claims have been identified at this time.

The member list needs to be amended since several WG members have missed more than two meetings and have not sent any comments to the drafts of the document.

There was a discussion of the tan delta values in Tables 4 to 6 in the latest draft. It was hoped to obtain the raw tan delta from outside North America and combine it with the existing data from within North America to produce one set of tables for the different types of cables. However the raw data was not available as it was proprietary to the utilities. As a result and as agreed at the last meeting the non-North American tan delta data have been placed in Annex G. . The referenced standard is for design – factory test data not field data – the reference needs to be removed.

Kent Brown presented tan delta data from new EPR cables, see Appendix F-5, for comparison with the values listed in Table 5. Testing of various lengths of new cable shows that the tan delta ranges from 0.0050 to 0.0120 and would be classed as “further study required” from Table 5.

Ben Lanz asked how short were cables that „challenged‟ the resolution of the test set. Kent Brown replied that lengths less than 50‟ gave higher than expected tan delta values– mostly due to the leakage at the terminations. The terminations on the test samples were heat shrink. Data from these short cables were censored out due to disparity in data from termination leakage.

There was concern that only one set of values was given in Table 5 to cover the different types of EPR, which were known to have different electrical characteristics. John Densley asked if data from different EPR types (different manufacturers – gray, pink, black) from an EPRI study should be included. The different types of EPR are listed separately but not much data on the time stability of the tan delta. The quorum of WG members present voted unanimously to separate the tan delta values of the different types of EPR as per the EPRI Tables. These values will be included in the next draft.

The issue of testing short cable lengths was raised. Should the minimum capacitance required for the test set (relates to the length of the cable) be stated or should the manufacturer of the test set determine what is the minimum length that can be tested? The latter was preferred as the minimum length could be dependent on the technology used.

It was agreed that information on how to perform the stability test will be added as it is not currently included.

After a lengthy discussion to include normalized or absolute tan delta values, it was eventually decided by vote to use absolute values for this revision but to consider normalized values in the next revision after more data are collected.

There was discussion concerning the intervals / number of steps for the ramp up.

Other decisions on the received comments were:

Section 5.2.4 – remove „tan delta‟ approved by vote (this section is about cosine rectangular).

Section 5.4.1 at end – add choices 5 & 6 comment to reword #2 to replace terminations with accessories and eliminate #6 – approved by vote.

Section 5.5.2 - remove the 1.5 U0 and use the withstand level; add comments to decide whether to continue to the withstand voltage if PD is seen, or keep the voltage maximum at the PDIV; remove the „transportable, discharge free‟ at the beginning.

Section 5.6.2 – reworded the first paragraph and will delete the second „new‟ paragraph. Change

the low frequency to 0.001 Hz. Remove the 2U0 reference.

Section 6 – OK as proposed.

Remove the phrase „PD Free‟ wherever it is in Section 5.5.1.

Table 3 – modify Footnote 1 as to equipment limitations.

Date for the next revision – by 11/30/10 – comments back by 1/31/11.

Minutes prepared by Tim Hayden, Vice-Chair.