Willem Boone, KEMA Diagnostic Services, Chalfont, PA ICC Fall 2000 Educational Program on PD Cable Diagnostics November

1. Very Low Frequency PartialDischarge Detection; an Experienced Diagnostic tool for Distribution Cables Willem Boone, KEMA Diagnostic Services, Chalfont, PA ICC Fall 2000 Educational Program on PD Cable Diagnostics November 1st 2000, St. Petersburg, Florida

2. Purpose of Diagnostic Testing • Principles of VLF testing Method • Test Results • Limitations and Innovative Developments • Cost/Benefit Evaluations • Future Developments • Conclusions

3. MAINTENANCE OPTIONS • Reactive maintenance, “wait-and-see” • Active maintenance, “predictive maintenance”

4. REACTIVE MAINTENANCE • To repair or replace if something is broken • Short term view (“no-health insurance”, “no-fire insurance”) • Short term benefit

5. ACTIVE MAINTENANCE • To avoid service failures • To specify network quality • To target replacement money • To improve customer satisfaction • To avoid customer claims

6. TO TRANSFER “MAINTENANCE” INTO “PREDICTIVE MAINTENANCE” IN ORDER TO REDUCE COSTS

7. HOW TO TRANSFER MAINTENANCEINTO PREDICTIVE MAINTENANCE Maintenance + diagnostic testing = predictive maintenance

8. PURPOSE OF DIAGNOSTIC TESTING • To avoid failures in service • To reduce costs • To target replacement money

9. Principles of present VLF diagnostic testing of cables

10. TRADITIONAL ONE-SIDED CABLE NETWORK DIAGNOSTICS defect 1 1 time

11. CABLE 0.1 Hz HV- supply PRINTER SCOPE PC MEASUREMENT SETUP

12. CHARACTERISTICS VLF PDD • Sine wave • Non-destructive • Off-lin

13. SYSTEM PARAMETERS • Maximum voltage 41kV, RMS • 0,1 Hz, sine wave • Discharge-free • Maximum cable length to be tested 15,000 ft • All type of cable or accessory, however defect should generate P.D. • Non destructive test (maximum test voltage 2x phase-neutral voltage)

14. KEMA VLF PD TESTING APPLICATIONS • PILC • All kinds of accessories • Both point to point and branched cable circuits • Very long cable lengths

15. ADVANTAGES OF 0,1 Hz POWERSUPPLY OVER 60 Hz VOLTAGE • Longer lengths of cable to be tested • Compact voltage source

16. TEST RESULTS • Test diagrams • Detected defects • Data base

18. BURNED PAPER

20. IMPLODED JOINT

22. CRACKED HOUSING

23. RECOMMENDATIONS • Replace/repair asap (<3 month) • Inspect asap • Retest (<2 year) • No action (retest < 5 year)

24. VLF PD - DATABASE • A database application for storage and consulting measured data of MV-powercables • Data are used to diagnose cable system including splices and termination • Actual condition of cable and/or accessory can be predicted from the measured data stored

25. Limitations of present VLF cable diagnostic testing • Only straight cable connections • Only cable lengths up to 14,000 ft

26. Principle of multi-terminal cable circuit diagnostics: • Two-sided • Branched

27. TWO-SIDED SYNCHRONISED CABLE NETWORK DIAGNOSTICS defect 2 1 1 2 time

28. BRANCHED CABLE NETWORK SYNCHRONISED DIAGNOSTICS defect 2 1 1 3 2 3 time

29. Trials in te USA to Test BCC-Diagnostics • September 1998 • April 1999

30. Improvements After First Trial • Coupling to the Tested Cable • Master/Slave Unit • Digital Filter

31. Improvements After the Second Trial • Software to Analyze Data • Remote Switching of Phases

32. KEMA - Diagnostic Services Branched Cable Testing

33. Introduction • General Test Procedure • Example Cable Map • Cable Tested Procedure • Results • Examples Taken From Actual Tests, In The USA, During The Past Year

34. General Test Procedure • Besides the 0.1 Hz voltage source used for the PTP testing, additional equipment is required such as a measuring node at each of the branches to be monitored. A node consist of: • GPS (Global Position System) Interface • Master-Slave Computer System • Communication Interface • Figure 1 is a schematic of a three-branched test set-up with one master node (#1) and two slave nodes (#2 and 3).

35. General Test Procedure

36. Sample Cable Map Example #1 • 5 Ended Distribution Cable • 4 Ends Have Cable Access • All Underground • Required 2 tests

37. Cable Tested Procedure Example #1

38. Results Example #1

39. Included In Test Report • Maps As Shown • Text Describing “Zones” • Summary Table

40. Sample Cable Map #2 • Multiple Ended Distribution Cable • 4 Ends Have Cable Access • All Underground • Required 3 Tests

41. Sample Cable Map/Test Procedure

42. Results Example #2 • The network was virtually divided into three Sections for the reporting purposes. • Test results and Mapping diagrams are presented individually for each Section.

43. Results Example #2 / Section #1

44. Results Example #2 / Section #2

45. Results Example #2 / Section #3

46. Included In Test Report • Maps As Shown • Text Describing “Zones” • Summary Table

47. Sample Cable Map #3 • Multiple Ended Distribution Cable • 2 Ends Had Cable Access • All Other Connections Required Utility To Cut Cable • All Underground • Required 4 Tests • Three Recording Nodes Were Used On Some Tests Sessions

48. Sample Cable Map

49. Cable Tested Example #3 / Test #1

50. Cable Tested Example #3 / Test #2