IQ_Partial_Discharge_Presentation (Phân Tích Phóng Điện Cục Bộ )

IQ Ser vices An Introduction to On-line Partial Discharge Surveys IQ Ser vices PARTIAL DISCHARGE When high voltage insulating material breaks down Partial Discharges are created, measured in units of charge known as pico-Coulombs or millivolts IQ Ser vices 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 IQ PARTIAL DISCHARGE TESTING USED FOR QUALITY ASSURANCE Ser vices • 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 IQ Ser vices IQ Ser vices NO OUTAGE EVALUATION These proven technologies exist today to evaluate medium or high voltage systems while the system is energized Oil testing/DGA – limited to oil transformers Infrared testing – visible loose connections only Visual inspections – problems may not be visible Power Quality – cannot detect insulation failures Vibration – limited to motors and transformers Partial Discharge Testing – single best all-around test IQ Ser vices 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 IQ Ser vices IQ Ser vices IQ Ser vices IQ Ser vices Insulator Failure Prevented IQ Ser vices Partial Discharge detection of a void in a shielded cable using inductive coupling Insulation Conductor Void Shield (grounded) + Detector Inductive Sensor IQ Ser vices IQ Ser vices High Frequency Current Transformer Used to Test Cable in High Voltage Substation IQ Ser vices Failing Terminations IQ Ser vices Molded Cable Accessory Failure IQ Ser vices Splice Void IQ Ser vices Shield Delamination Causing Partial Discharge IQ Ser vices Poor Workmanship Causing Partial Discharge IQ Ser vices Case Study Testing 15kV cables On-line testing of cables PD damage to termination Ser vices Identifying & Prioritising Circuits Most at Risk Using On-Line PD Survey LIVE LINE PARTIAL DISCHARGE SURVEY RESULTS OF 629 HV FEEDERS 1000 900 800 700 600 500 400 300 ACTION 200 FEEDERS 10 58 56 54 52 84 63 442 21 00 37 358 337 316 295 274 53 32 11 19 16 14 12 10 84 63 42 21 50 CONCERN 100 m V Dis c rg e IQ IQ Ser vices PD Survey - Worst 30 Results LIVE LINE SURVEY WORST 30 RESULTS 1000 900 m V DIS CHAR GE 800 700 600 500 400 300 200 100 Tripped and consequences within months Tripped Wet cable Tripped Discharging joint Tripped IQ Ser vices 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 IQ Ser vices 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 IQ Ser vices   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!   ... Propagation of Transient Earth Voltages (TEV) in Switchgear High Voltage Bus Partial discharge site (inside) Metallic Switchgear cover (signal detected outside) IQ Ser vices Measurements using Capacitive... (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... Circuit Breakers Disconnect Switches Insulated Switchgear Bus Bus duct Cable Cable Joints (splices) Cable Terminations Based on IEEE Gold Book Table 36 Percentage of insulation failure 84% 21% 15%