IQ_Partial_Discharge_Presentation.ppt
- 1. I Q S e r vic e s An Introduction to On-line Partial Discharge Surveys
- 2. I Q S e r vic e s PARTIAL DISCHARGE When high voltage insulating material breaks down Partial Discharges are created, measured in units of charge known as pico-Coulombs or millivolts.
- 3. I Q S e r vic e s WHAT IS PARTIAL DISCHARGE? • Electrical discharges occurring inside medium and high voltage insulation (flaws, cracks, voids, irregularities). • These imperfections create voltage stresses and cause eventual failure of the insulation. • Insulation failures begin with and are characterized by small but detectable releases of energy or Partial Discharge.
- 4. I Q S e r vic e s • For many years partial discharge testing has been an IEEE/ANSI standard to identify insulation problems in electrical apparatus before it leaves the factory floor. • Many U.S. and International standards have been developed for partial discharge testing. • Until recently Partial Discharge testing was limited to testing at manufacturer’s laboratories. • Now computers and sophisticated equipment can isolate and detect Partial Discharge occurrences in the field. PARTIAL DISCHARGE TESTING USED FOR QUALITY ASSURANCE
- 5. I Q S e r vic e s
- 6. I Q S e r vic e s NO OUTAGE EVALUATION These proven technologies exist today to evaluate medium or high voltage systems while the system is energized. 1. Oil testing/DGA – limited to oil transformers 2. Infrared testing – visible loose connections only 3. Visual inspections – problems may not be visible 4. Power Quality – cannot detect insulation failures 5. Vibration – limited to motors and transformers 6. Partial Discharge Testing – single best all-around test
- 7. I Q S e r vic e s PARTIAL DISCHARGE VS. INFRARED How are Partial Discharge Inspections different from Infrared Inspections? • Infrared identifies electrical current problems (loose connections) that result in heat. The specimen must be visible to the naked eye for the infrared camera to detect a problem. • Partial Discharge identifies voltage problems that result in insulation breakdown and generation of Partial Discharges. The specimen does not need to be visible for Partial Discharges to be detected.
- 8. I Q S e r vic e s
- 9. I Q S e r vic e s
- 10. I Q S e r vic e s
- 11. I Q S e r vic e s
- 12. I Q S e r vic e s INSULATION BREAKDOWN Why should we be concerned with insulation breakdown and Partial Discharges?
- 13. I Q S e r vic e s • NFPA 70B states that insulation breakdown is the number one cause of electrical failures. • In medium and high voltage equipment, partial discharges are the first indication of insulation breakdown. INSULATION BREAKDOWN
- 14. I Q S e r vic e s Component Percentage of insulation failure Transformers 84% Circuit Breakers 21% Disconnect Switches 15% Insulated Switchgear Bus 95% Bus duct 90% Cable 89% Cable Joints (splices) 91% Cable Terminations 87% Based on IEEE Gold Book Table 36 Total Failures due to Insulation Breakdown
- 15. I Q S e r vic e s WHAT TYPE OF FACILITES ARE AFFECTED? • INDUSTRIAL - Large Manufacturing, Cogeneration • COMMERCIAL - Research Parks, High Rises • INSTITUTIONAL - Campuses, Hospitals • GOVERNMENTAL - Military Bases, Large Office Complexes • UTILITY - Investor Owned, Municipalities
- 16. I Q S e r vic e s WHERE DO PARTIAL DISCHARGES OCCUR? • Electrical Systems > 600V (2.4KV, 4.16 KV, 12KV, etc.) • Types of Equipment Subject to Partial Discharge -Cables -Transformers -Circuit Breakers - Instrument Transformers -Switchgear (CT’s, PT’s) -Insulators - Bushings -Generators - Motors -Surge Arrestors - Capacitors
- 17. I Q S e r vic e s ADVANTAGES OF PARTIAL DISCHARGE SURVEYS • PREDICTIVE - failures can be prevented. • NO OUTAGE NECESSARY - does not interrupt operations. • NON-DESTRUCTIVE - no damage to electrical system. • TRENDING - comparison to previous tests possible • PRIORITIZE MAINTENANCE ACTIVITIES - determine which equipment to service first. • PLANNING - allows time to schedule repairs. • FINANCIAL CONTROL – repairs can be budgeted.
- 18. I Q S e r vic e s TYPICAL MEDIUM VOLTAGE POWER CABLE CONSTRUCTION
- 19. I Q S e r vic e s Source Switchgear Ground Level Underground Cable in Conduit (not visible) Visible Cable Terminations Load Unit Substation Visible Cable Terminations TYPICAL HIGH VOLTAGE UNDERGROUND CABLE SYSTEM
- 20. I Q S e r vic e s 3 STAGES OF CABLE INSULATION FAILURE
- 21. I Q S e r vic e s STAGE 1 Imperfections and voids voids INSULATION / / / /CONDUCTOR / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / INSULATION No problems, minor voids therefore minor partial discharges Jacket, Shield, Semi-conducting shield Jacket, Shield, Semi-conducting shield
- 22. I Q S e r vic e s INSULATION / / / /CONDUCTOR / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / INSULATION Tracking begins Jacket, Shield, Semi-conducting shield Jacket, Shield, Semi-conducting shield STAGE 2
- 23. I Q S e r vic e s INSULATION INSULATION CABLE FAILURE! Jacket, Shield, Semi-conducting shield Jacket, Shield, Semi-conducting shield Blow-up Phase-to-ground / / / /CONDUCTOR / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / STAGE 3
- 24. I Q S e r vic e s HOW CAN PARTIAL DISCHARGES BE DETECTED? Discharges are detected by special signal processing equipment designed to eliminate outside interference. Capacitive Methods - For Unshielded Components - Dry Type Transformers - Instrument Transformers - Switchgear Inductive Methods - metal enclosed components - Shielded Cables and Components - Oil Filled Transformers - Rotating Apparatus Acoustic Emission Methods - Dry & Oil Transformers - Switchgear - Unshielded Cables
- 25. I Q S e r vic e s Test Equipment & Sensors
- 26. I Q S e r vic e s Partial Discharge detection of a flaw in a dry type transformer using capacitive coupling flaw Transformer Coil Capacitive sensor Detector
- 27. I Q S e r vic e s High Voltage Bus Metallic Switchgear cover (signal detected outside) Partial discharge site (inside) Propagation of Transient Earth Voltages (TEV) in Switchgear
- 28. I Q S e r vic e s Measurements using Capacitive PD sensors
- 29. I Q S e r vic e s Switchgear failure due to internal tracking
- 30. I Q S e r vic e s Tracking on epoxy resin busbar
- 31. I Q S e r vic e s Start of tracking on insulation
- 32. I Q S e r vic e s Failed Switchgear Insulation
- 33. I Q S e r vic e s Detecting PD Using Airborne Acoustic (Ultrasonic) Sensors Insulator Busbar Sensor
- 34. I Q S e r vic e s Airborne Acoustic Sensor
- 35. I Q S e r vic e s Insulator Failure Prevented
- 36. I Q S e r vic e s Partial Discharge detection of a void in a shielded cable using inductive coupling. Insulation + Void Shield (grounded) Conductor Detector Inductive Sensor
- 37. I Q S e r vic e s
- 38. I Q S e r vic e s High Frequency Current Transformer Used to Test Cable in High Voltage Substation
- 39. I Q S e r vic e s Failing Terminations
- 40. I Q S e r vic e s Molded Cable Accessory Failure
- 41. I Q S e r vic e s Splice Void
- 42. I Q S e r vic e s Shield Delamination Causing Partial Discharge
- 43. I Q S e r vic e s Poor Workmanship Causing Partial Discharge
- 44. I Q S e r vic e s Testing 15kV cables On-line testing of cables PD damage to termination Case Study
- 45. I Q S e r vic e s Identifying & Prioritising Circuits Most at Risk Using On-Line PD Survey L IV E L INE P ART IAL D IS C HARG E S URV E Y RE S UL T S O F 6 2 9 HV F E E D E RS 0 100 200 300 400 500 600 700 800 900 1000 1 2 1 4 2 6 3 8 4 1 0 5 1 2 6 1 4 7 1 6 8 1 9 0 2 1 1 2 3 2 2 5 3 2 7 4 2 9 5 3 1 6 3 3 7 3 5 8 3 7 9 4 0 0 4 2 1 4 4 2 4 6 3 4 8 4 5 0 5 5 2 6 5 4 7 5 6 8 5 8 9 6 1 0 FEEDERS m V D i s c h a rg e A C TIO N C O N C E RN
- 46. I Q S e r vic e s PD Survey - Worst 30 Results
- 47. I Q S e r vic e s PERFORMING A PARTIAL DISCHARGE SURVEY • Analyze the single line drawing to develop plan • Onsite Measurement – Removal of equipment covers. – Record field data. – Obtain signatures of atypical components. • Offsite Data Analysis – Correlate measurements to single line drawing. – Compare atypical results to like insulation from database. – Analyze signatures. – Trend Results. • Report Generation – Recognize immediate failure possibilities. – Recommend possible repairs. – Recommend possible resurvey frequency.
- 48. I Q S e r vic e s SUMMARY • Electric Insulation will fail. • Predicting failures is now possible through Partial Discharge Analysis. • No outage is required to survey the equipment. • Results can be prioritized and trended. • Partial Discharge Surveys should be performed annually.
- 49. I Q S e r vic e s We apologize to every electrical professional for taking 252 years to prevent your failures. Benjamin Franklin discovered electricity in 1752. This year we launched an easy to use, cost effective “no-outage” electrical inspection technology that detects medium and high voltage equipment problems before they fail!