1. Jicable11, 19 - 23 June 2011 - Versailles - France MODERN METHODS OF INSTALLATION AND DIAGNOSTIC TESTING OF DISTRIBUTION POWER CABLES Edward GULSKI, onsite.hv.solutions, Switzerland Frank DE VRIES, Alliander, The Netherlands Piotr CICHECKI,, onsite.hv.solutions Benelux, The Netherlands Johan J. SMIT, TU Delft, The Netherlands

2. Jicable11, 19 - 23 June 2011 - Versailles - France CONTENT Introduction Testing with DAC (OWTS) Standards and knowledge rules for after installation tests Standards and knowledge rules for diagnostic tests Practical example Conclusions Future steps

3. Jicable11, 19 - 23 June 2011 - Versailles - France INTRODUCTION Biggest DSO in the Netherlands Over 35000km MV cable circuits MV levels: 6, 10, 20 and 50kV 15 years experience in PD measurements on MV cables 3 teams specialists Over the last 10 years more than 3500 cables have been diagnosed with DAC

4. Jicable11, 19 - 23 June 2011 - Versailles - France TEST PRINCIPLE OF DAC (OWTS) L C cable wifi Computer U & PD Solid state switch HV Source

5. Jicable11, 19 - 23 June 2011 - Versailles - France PD MEASUREMENT WITH DAC (OWTS) Testvoltage PD activity

6. Jicable11, 19 - 23 June 2011 - Versailles - France IMPORTANT PARAMETERS PD inception voltage (PDiV) PD extinction voltage (PDeV) PD level @ Uo PD level vs Testvoltage Phase resolve pattern PD location

7. Jicable11, 19 - 23 June 2011 - Versailles - France

8. STANDARDS FOR AFTER INSTALLATION TESTS ON NEW CABLES Based on NEN3620 –Voltage Withstand Test cablesheath 5kVDC-5 min –Voltage Withstand Test main insulation 3xUo, 0,1Hz-15min or 50 cycles 3xUo DAC –PD measurements 0,25-0,5-0,75.....2xUo Voltage withstand tests –Simple rule accepted / rejected –Destructive method –Not monitored PD measurements –Monitored test method –Gives information about abnormalities –Interpretation of results is complex Alliander: All new cablecircuits are tested according NEN3620 also PD measurement are performed on new cable circuits that include joints

9. Jicable11, 19 - 23 June 2011 - Versailles - France PDiV < 1,7xUo RejectedAccepted PDiV > 1,7xUo Decision process for PD testing with DAC After laying testing of new Cable circuits: XLPE insulation

10. Jicable11, 19 - 23 June 2011 - Versailles - France PDiV < 1,2xUo RejectedAccepted 1,2xUo < PDiV < 1,7xUoPDiV > 1,7xUo PD intensity > 3 per cycle ? no yes Decision process for PD testing with DAC After laying testing of new Cable circuits: Cable joints PD magnitude > 100pC ? no yes no Repetition of test possible? yes Test repetition

11. Jicable11, 19 - 23 June 2011 - Versailles - France COMPANY STANDARDS FOR DIAGNOSTIC TESTS ON AGED CABLES For XLPE cable circuits –Voltage Withstand Test on cable sheath 5kVDC-5 min –PD measurements up to 2xUo* For PILC circuits –PD measurements up to 2xUo* –TanD measurements up to 2xUo* –Voltage withstand test with DC 2xUo2* 5 minutes, VLF 2xUo* 5 minutes or DAC 2xUo* 50 cycles * Or lower testvoltage in case of safety aspects Alliander: Only suspicious cablecircuits are diagnosed. * Or lower testvoltage in case of safety aspects

12. Jicable11, 19 - 23 June 2011 - Versailles - France DEVELOPMENT OF KNOWLEDGE RULES FOR DIAGNOSTIC TESTS Knowledge rules -Statistics -Component investigations -Determination -Statistic boundaries -Physics of PD processes -Component properties (design and materials) -Operation parameters -Escalation (destructive tests) -Fundamental tests -Behaviour of different PD types Predict Theoretical information Test Laboratory tests Evidence Failure information Detect Measurement data

13. Jicable11, 19 - 23 June 2011 - Versailles - France PRACTICAL EXAMPLE PD activity in a joint Cable circuit in Alkmaar area: - 10kV PILC 3x95Cu and 3x150AL - 4 joints (different types of oil joints) Interruption caused by external damage. After repairing the failure the cable sometimes broke down at 1,5Uo during the DC voltage test. Localisation of breakdown was difficult. We applied PD measurement on the cable to detect the problem. Joint 1: 260m Joint 2: 310m Joint 3: 650m Joint 4: 700m 1100m

14. Jicable11, 19 - 23 June 2011 - Versailles - France PRACTICAL EXAMPLE Advise and taken action Failure information Measurement data Based on experiences joint 2 was replaced. However joint 1 had much higher max PD magnitude than joint 2 !!! After replacing joint 2 no problems occurred in the circuit. Joint 1 type A: 24000pC Joint 2 type B: 6000pC

15. Jicable11, 19 - 23 June 2011 - Versailles - France CONCLUSIONS Combining PD measurements with withstand tests give much more information about the quality of the components After installation testing and diagnoses of new and old MV cable circuits by means of DAC gives reliable results Knowledge rules are developed for the determination of the condition of new and old cables and accessories

16. Jicable11, 19 - 23 June 2011 - Versailles - France FURTHER STEPS Pilot project in 2011: implementation of DAC diagnoses on old 50kV XLPE cable circuits –25 measurements –Development of knowledge rules –Condition evaluation and proposal for the future Consider to implement DAC technology for after installation test procedure on 50kV cable circuits

17. Jicable11, 19 - 23 June 2011 - Versailles - France THANK YOU FOR YOUR ATTENTION For more information: frank.de.vries@alliander.com