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WG B1.25 Advanced Design Of Laminated Metallic Coverings

WG B1.25 Advanced Design Of Laminated Metallic Coverings. Minutes of the third meeting of WG B1-25 Cologne– 01&02 April 2008 1 pm – 12am next meeting : Delft 5 and 6 June 2008; starting at 1pm on 5th June and closing at 12am on 6th June. WG B1.25 Attendee.

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WG B1.25 Advanced Design Of Laminated Metallic Coverings

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  1. WG B1.25 Advanced Design Of Laminated Metallic Coverings Minutes of the third meeting of WG B1-25Cologne– 01&02 April 20081 pm – 12am next meeting : Delft 5 and 6 June 2008; starting at 1pm on 5th June and closing at 12am on 6th June

  2. WG B1.25 Attendee Matthias KIRCHNER Germany Ernesto ZACCONE Italy (on behalf of Giovanni POZZATI) Frank MIDDEL Netherlands Hans MAYER Australia Johan KARLSTRAND Sweden Bruno FAINARU Israel Kenichiro TANIMOTO Japan Kenneth BOW USA (first day) Pierre MIREBEAU Convener Jean BECKER Secretary Excused : Matthieu SURDON from France

  3. WG B1.25 – Documentation and reports (reminder) Website • http://www.cigre-b1.org/ • WG area • WG B1-25 • Password : "screen" for reading • pierre.mirebeau@nexans.com

  4. WG B1.25 Agenda 1. Welcome 2. Examination / comments of WG documents : Last meeting minutes Examination of action list 3. Updated recommendation : Content discussion (continuation) 4. Update on tests: Discussion on comments and input from full members not present at last meeting and corresponding members Any method of any need when taking into account the operation feedback ? 5. Update on feedback : Discussion on draft prepared by Frank 6. Date and location of the next meeting .

  5. WG B1.25 1. Welcome We thank our German friend Matthias for his invitation and the perfect organisation of the meeting

  6. WG B1.252. Examination / comments of WG documents : 2.1. Last meeting’s minutes: Bruno FAINARU was present at the second meeting, he has been added to the Attendee list. No other remark. The second meeting’s minutes are approved: see WEB pages of WG B1-25

  7. WG B1.25 2. Examination / comments of WG documents : 2.2. Examination of decision/action list and the comments from the members on second meeting’s minutes

  8. DECISION LIST OF THE SECOND WG B1-25 MEETING HELD IN STOCKHOLM (KISTA) On October 9 and 10, 2007 Answers or decisions(in blue)

  9. DECISION LIST OF THE SECOND WG B1-25 MEETING HELD IN STOCKHOLM (KISTA) On October 9 and 10, 2007 Continued (Answers in blue)

  10. SECOND WG B1-25 MEETING’S MINUTES from October 9 and 10, 2007 in Stockholm 2.2.Comments from members Giovanni Pozzati: I haven't special observations Other answers concerning Second meetings minutes: Pag. 15: •Bending test : OK. Question : what about a bending on 20 (D+d) ? In our experience 20 is OK Impact test TI agree with the proposal, but identify the classes: A) 5 kg/1 m for copper wires plus laminated foils (present technical report ); B) 27kg/ 0.27 m for laminated foils (sheath) only.4 times (safety reasons Pag. 16: Sidewall pressure test It is better to keep this test: at least this is a reference and gives information about the test procedure and maximum acceptable level. Corrosion test after impact or sidewall pressure test The procedure to submit sample to bending and impact test before the corrosion test has to be maintained: it's representative of what can happen during installation. Adhesion strength of metallic foil 1.5 N/mm is OK Pag. 17 Screen contact resistance The test is not needed but I think it's necessary to specify that laminated foils shall be bonded to the wires at each accessory. 

  11. SECOND WG B1-25 MEETING’S MINUTES from October 9 and 10, 2007 in Stockholm 2.2.Comments from members (continued) Hans A Mayer: No special observations Bruno Fainaru : no special observation Johan Karlstrand: No special observation. I will check the proposed peel strength value of 1.5 N/cm. Mathias Kirchner: No special observation. KenBow I want to comment on the 1.5 N/mm peel. In the US the number has been 1.75 N/mm for the bond of the cable covering to the metallic tape. It has been demonstrated that mechanical performance of the cable improves with higher bond strengths between the plastic covering and the tape. I assembled the data on usage for the IEEE guide. These data are for one European cable maker selling laminate sheaths. They represent their sales, not a compilation of statistics on usage from the cable users. It is the trend that is being conveyed by the data. Some statistical data from the users would be nice, but it would have to be compiled, and I do not have the ability to do this. Are there independent sources that could be contacted USA: Adlmco 2 type

  12. Answer from USA during meeting 3 Your experience regarding cables with laminated screens - USA • Voltage: • 69, 138, 345 kV • Design: • Insulated core (138 kV with reduced insulation wall thickness) • Copper Wires (round or flat) • Semicon swellable tape • 0.15 mm coated copper, one side coated, 0.05 mm coating • Sealed overlap with hot melt adhesive • HDPE outer covering • Reference Standard: • IEC 60840 • AEIC CS5 • Laying Conditions: • Pulled into ducts • Cross-bonded This slide will be added to first minutes meeting

  13. Standards IEC 60840 The Swedish one is rarely used. Answer from Japan during meeting 3 Your experience regarding cables with laminated screens - Japan • Voltage • XLPE insulation, Umax : 66-275 kV • 2 different designs: lead foil (66-154 kV, since 1985); Aluminium foil (66-275 kV, since 1998 • Design (Almco 3) • XLPE insulation • Round copper wires screen, non swelling semi-conductive tape below • 0.2 mm thick lead or Alu foil with glue on one side, inner side (screen side) coated with 0.05 mm thick semi-conductive plastic to avoid corrosion • Overlap 20 mm, no additional glue at overlap • Short circuit calculation without the laminate : 250°C maximum temperature on the wires • Over-sheath : flame retardant PVC • Aluminium foils become major, but some utilities still use lead foils This slide will be added to first minutes meeting • Reference standards • 66-77 kV: General Japanese standard; above 77 kV, Utility standards • Bending test 5 times both directions on a mandrel with a diameter of 10 times the screen diameter (max): criteria: no cracks on metal foil; foil shall not be removed easily by hand; no crease on foil • Moisture barrier test : 30 cm of cable sheath sealed with silica gel inside; sample immersed in water at 60°C; weight difference of absorbent measured after 10days, 20 days and 30 days • Laying conditions • Connection to accessories: remove semi-conductive layer, lead soldered to braided earthing wire, Aluminium connected with a clip to braided earthing wire.

  14. Discussion on spike test • This test is asked by certain Utilities in UK, but scope is not clear. • Information on why this test is in the UK specifications to be gathered from Vic Banks or Steve Swingler if possible • No electrical accident is known by members of WG.. • N.B. A number of people have died because of overhead lines and low voltage cables (Italy) Nobody heard that in the last 40 years anybody died because of a damage on underground HV cable • General Cable has made this type of test in the 1970th on MV cables. Why?

  15. Discussion on peel strength of laminates in different countries • IEC: prescribed adhesion strength value is 0.5 N/mm between over-sheath and laminate, and at overlap of laminate • Germany: 0,5 N/mm at ambient- to be checked for higher temperatures. Bending test 20 (D+d). Experience OK, What about actual peel strength, which is not necessarily the same as the prescribed value!!. • Japan: would have difficulties to pass 1.5 N/mm at the overlap as there is low adhesion there (no extra glue at overlap to improve the adhesion strength). Maybe this is the reason why GT 21-14 from CIGRE adopted 0.5 N/mm as a compromise!? • USA:. Ken B. reports that in the US the number has been 1.75 N/mm for the bond of the cable covering to the metallic tape. It has been demonstrated that mechanical performance of the cable improves with higher bond strengths. Ken Bow has made peel tests in relation to temperature. He will check whether he has a paper on the subject • In ground the temperature at the screen is 80°C for EHV cables for maximum service current. Need for special hot melt to withstand this high temperature. • Ernesto: As type 1 screen also has a screen function, prescription for peel strength shall be severer than for the two others, where the screen function is separated from the tightening function

  16. Discussion on peel strength of laminates in different countries (continued) • It has been decided that each member gives his opinion/practice by filling tables for next meeting: Peel strength needed for each type of laminate design and depending for the different metals involved, at room temperature and 80°C

  17. Experience with cables with laminate coverings • 1. Inquiry (see point 5) • 2. The system view

  18. The System View • The following items shall be considered: • Type of accessories. • Inclusion of system tests in standards • Short circuit tests with accessories • Sealing against water and corrosion at the accessories • Designs to be avoided (ex.: lapped copper tape under one side coated laminate – or no connection between wires and metallic foil at the accessories). • Types of laying and grounding. • Stiffness (no issue actually)

  19. The System ViewContinued • Type of accessories: list + functional description: the detailed description • shall be in the performance test report, not in the our WG recommendation (as well as cable design – detailed laminate covering description). • Inclusion of system tests in standards: should be a must • Short circuit tests with accessories: Performance of the screen with calculated rating (is IEC 61443 calculation applicable for everybody ?) to reach the temperature limit. Lower temperature limits are validated by the higher one. Short circuit temperatures actually used to be included. Present short circuit limits are: -IEC 150°C -Italy, France, Germany (open circuit), Israel, Sweden, NL for wires: 250°C -Germany (closed circuits): 350°C on copper wires • Circulating current: • Design 1 : avoid pressure contact or test the connection. • Design 2 : movement of the laminate might be critical for the contact.--> provision to be taken i.e. clamping close to the connection. • To review the Norwegian case next time.

  20. The System ViewContinued • Sealing against water and corrosion at the accessories: covered by the IEC test for buried joints, and additional evidence is given at the examination at the end of prequalification test (case of 62067). • Designs to be avoided (ex.: lapped copper tape under one side coated laminate – or no connection between wires and metallic foil at the accessories when there is no direct contact in the cable). Look for paper in ETZ (Mathias) • Types of laying and grounding. • For type 1 and 2 all typesof laying • For type 3: ducts and tunnels (reason for no direct burying to be checked by Ken T. • Sidewall pressures used: to be checked in inquiry • Stiffness (no issue actually, annealing?) • Conclusion: after inquiry

  21. WG B1.25 3. Recommendations Full members not present at the meeting and corresponding members are invited to give their comments and inputs to the items of chapter 3 (Recommendations), if possible before next meeting, 5 and 6 June 2008, so that we can integrate them into the report of third meeting N.B. In blue you will see what has been discussed during third meeting

  22. WG B1.25 . Recommendations • 3. Recommendations • (in red test recommended by WG B1-25 either as development test D, as type test T or as sample test S N.B. no routine test applicable) • 3.1. Tests on cables • 3.1.1 Development tests • Bending test : OK. In principle • Bending diameter: 20 (D+d) OK for design 1 and 2 ; 10 D for design 3 (see Japanese specs) • Thermal cycle test: fatigue proven to be not an issue (Electra 141, but decrease of peeling strength in case of bad design  test replaced by ageing test and peeling measurement). covered by the 3000h ageing test at 70°C and 80°C • Longitudinal water penetration test. Refer to IEC • DImpact test., 2 classes to be considered depending on the design for safety reasons: standard type : • for design: 2, 5kg dropped from 1m height on cable sample; • For design 1: 27kg weight dropped from 27cm height on cable sample, 4 times on the same place • For design 3: no impact test, because of the restrictions on installation conditions

  23. WG B1.25 Discussion on content 3. Recommendations3.1. Tests on cable 3.1.1 Development tests (continued) • D Short circuit testgo to short circuiton the system • Motivation for this set of parameters : low cost test and many laboratories available. • Short circuit on the system is enough (no specific short circuit on the cable). • 5m of cable with a joint and/or the termination connection At least 2m of cable each side of the joint. • Rating determined by calculation • The cable conductor shall be heated and stabilized for at least 2 h at a temperature 90 to 95°C. • 5 short circuits. • Cool within 10K of initial screen temperature. • Maximum short circuit duration : 5s • Asymmetry: free • Validation rule: lower temperature and lower maximum current • Connection testing: see next meeting

  24. WG B1.25 Discussion on content 3. Recommendations3.1. Tests on cable 3.1.1 Development tests (continued) • DSidewall pressure test See Italy and Japan to know if it is discriminating between good and bad cables; if not, this test is useless because it was not used during 10 years and there was no practical problem. (!?) • According to experience, the test is not necessary, but if the requirement is higher than the experience the test has to be performed give the level that has been experienced for next meeting (each member) and the test has to be better defined as well (e;g; distance between rollers) • We take the text from E 141 adding a lower limit and the distance between rollers (see distance on site during installation)  distance for next meeting. • TLong term ageing of the bonding after impact or sidewall pressure testpreconditioning is not necessary. Test on fresh cable is enough. In close trefoil formation actual sheath temperature is 80°C, so the group recommended temperature for corrosion is 80°C 3 ?, and peel strength to be checked at the end of the test. • 70°C 3 for flat formation and 80°C 3 for trefoil. • All designs

  25. WG B1.25 Discussion on content 3. Recommendations3.1. Tests on cable 3.1.1 Development tests (continued) T + SAdhesion strength of metallic foil. Proposal is to recommend a peel strength of 1.5N/mm, at room temperature. Proposal to adhesion test at high temperature and ageing test. Members have to check it(table to fill in) Adhesion strength of overlapped metallic foil: same as adhesion test (table to fill in) Moisture penetration: HD 620 part 6J. appendix F.4. Determination of the water permeability coefficient of the non-metallic sheath. This test is to be performed within the WG on a cable with overlapped laminate to make clear whether it is useful to recommend it. Not needed with evidence given by Johan and Pierre TScreen contact resistance (under development in Electra 141)  addressed by the PD test at the end of the type test. Made initially for designs where the wires are not connected to the metallic foil at the accessories. Now every people makes the connection in HV. The test is not needed any longer.?

  26. WG B1.25 Discussion on content 3. Recommendations3.1. Tests on cable 3.1.1 Development tests (continued) TFatigue : to be discussed when receiving all the following papers: B1-111 (on WEB site), ELT 140 (Johan), CS9 (draft G on WEB site) , IEEE PES 96 nb1 and IEEE PES 99 nb6 IEEE PES 96 nb1 (Pierre Argaut), JICABLE 03 p A-1-5 from J Power (Pierre) and ICEA S -108 - 720 (Bruno). Experience has shown that 20 cycles are enough  we align with IEC TR Spike test : Ask to Steve or Vic whether this test has failed in practice. For the attending members, it is useless. (Kema did it for one customer, Bruno will make a test in Kema in May 08) Some UK customers want to keep it The scope is linked to safety management. Not specific to this type of screen : no conclusion at the meeting DAbrasion test : Not useful for PVC or PE sheaths (IEC 60229 Paragraph 4.1). To be performed on new material (e.g. ST8)

  27. WG B1.25 Discussion on content 3. Recommendations3.2. Tests on cable system 3.2.1 Development tests • 3.2. Tests on cable system • 3.2.1 Development tests • Short circuit tests with accessories • Sealing against water and corrosion at the accessories • Thermal cycle test • Thermomechanical test 62067  addressed in prequalification test • 60840 

  28. WG B1.25 Discussion on content 3. Recommendations3.2. Tests on cable system 3.2.2 Requirements 3.2.2 Requirements(not discussed) 3.2.2.1 Type test 3.2.2.2Sample test 3.2.2.3 Routine test (not applicable)

  29. WG B1.25 Discussion on content 4 Guide to use 4. Guide to use(not discussed) 4.1 As a function of laying conditions 4.2 As a function of customer requirements

  30. INQUiRY. Questionnaire on Feedback on experience with laminated covering designs in the field • A questionnaire on feedback on experience with laminated coverings has been prepared by Frank and presented during the meeting (See annexed Exel page). It has been accepted by the Working Group. • The members of the WG are invited to fill in this document before next meeting for their countries: send document filled in to Pierre and Jean. • Pierre will send the document to Study Committee B1 to get also information from other national member countries • Jean will collect all data for next meetingand present an overview of results of inquiry (if available) • A suggestion from Ernesto is to take the table on large projects from CIGRE Technical Brochure 338, add a column with the type of screen used for the cables. This would give already a good overview on the use of laminated coverings in HV and EHV systems. Members to make this exercise for the large projects of their countries. Jean will collect the results

  31. Next meeting • Next meeting will take place in DELFT (Netherlands) on invitation by Frank on 5 and 6 June 2008,starting at 1pm on 5th June and closing at 12am on 6th June. • A number of tasks shall be performed as homework before next meeting; A decision list as been prepared and we ask all members to send their answers to Pierre and Jean

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