Parfcial Discharges in Electrical Power Apparatus

Transcription

1 Parfcial Discharges in Electrical Power Apparatus Univ.-Prof. Dr.-Ing. Dieter König Prof. Dr.-Ing. Y Narayana Hao vde-verlag gmbh Berlin Offenbach

2 Contents Foreword 3 1 The Phenomenon of Partial Discharges By Prof. Dr. D. König Introduction Definition of terms Typical electrode configurations with partial discharges Internal discharges and surface discharges External discharges Equivalent circuits Internal discharges and surface discharges External partial discharges PD characteristic parameters Waveform and charge of an individual PD current pulse Train of PD current pulses Train of PD current pulses in relation to the temporally assigned instantaneous value of the high voltage Non-electrical PD characteristic parameters Conclusions References 37 2 Fundamentals of Partial Discharge Measuring Techniques By Dr. K. Schon Introduction Waveform and spectrum of partial discharges PD charge measuring equipments Integration in the frequency domain Selectively wideband System Narrow-band System Integration in the time domain with very large wideband Systems Summarising evaluation of the measuring instruments Measuring impedance or coupling 4-terminal device PD-measuring circuits Calibration Calibration pulses Calibration of the PD-measuring set-up Calibration.in the complete test set-up Uncertainty of measurement References 59

3 3 Screening and Filtering Problems during Partial Discharge Measurements By Prof. Dr. D. Peier Introduction Need for screening Design of screens Completely enclosed screen Screen interruptions Effect ofcorners Cavity resonance Design of filters Measurement of screening efficiency Realized examples Screening Ventilation Doors Lead-through bushings Summary References 77 4 Effects of Partial Discharges on Electrical Insulating Materials By Prof. Dr. K. Möller and Dr. D. Meurer Introduction Gaseous insulating materials Liquid insulating materials Solid insulating materials Surface discharges Internal discharges Mixed dielectrics Summary References 95 5 Evaluation of Partial Discharges By Dipl.-Ing. P. Blasius and Dr. K.-H. Weck Introduction Relation between measured and actual charge Relation between the time-dependent occurrence of PD and the extent of damage due to it Summary and conclusions References 113

4 6 Status of National and International Partial Discharge Test Specifications By Dr. K. Schon Historical development Standardisation Historical IEC Publication DIN VDE 0434/ Inferences Specifications for some power apparatus and Systems References Partial Discharges in Bushings and Capacitors By E. Kronen and Dr. F. Hammer Requirements for the PD quality Proof of the PD quality Disturbances during PD measurements Partial Discharges in Insulation of Rotating Machines By Dr. A. Wichmann Verification of partial discharges Voltage-dependence of loss factor and capacitance Conclusions from the loss factor increment Evaluation of the manufactured quality Production control by loss factor measurement Detection of PD by the high frequency measuring technique Investigations on model configurations Measurements on winding elements Location of partial discharges PD measurements for monitoring in service References Measurement and Location of Partial Discharges in Cables By Dipl.-Ing. H. Kober Need for PD measurement Development of PD-measuring techniques in cables Problems during PD measurements on long cables Refiections and superposition effects Damping National and international specifications Specifications for test methods Permissible PD magnitudes Location of partial discharges 165

5 l Methods of locating partial discharges PD location according to pulse spacing method Summary References Partial Discharges in Cable Accessories By Dipl.-Ing. C. van Hove General PD behaviour of cable accessories and possibilities of influencing it PD test according to DIN VDE References Partial Discharges in Current and Voltage Transformers By Dr. H.-J. Voß Causes of partial discharges in instrument transformers Internal partial discharges PD in cast resin-impregnated instrument transformers PD in oil-insulated instrument transformers PD in SF 6 -insulated instrument transformers External PD in instrument transformers PD due to poor potential grading Measurement of PD in instrument transformers Test circuits Special tests for location of PD Specifications * References Partial Discharges in Transformers By Dr. K.-H. Fellmann Test Standards PD sources in transformers Measuring methods Narrow-band measurement Wideband measurement Radio interference meters Calibration and measurement Calibration according to IEC Calibration according to NEMA Measurements and influencing parameters Requirements for the measuring instruments Requirements for the test bay Preparation of the test object

6 Performing PD measurements Possible disturbances Disturbance sources Locating disturbance sources PD measurements during direct voltage tests Reasons for the test Typical test procedure and PD requirements Test set-up and coupling of PD meters Requirements for the measuring System Location of partial discharges Electrical location Acoustic location :2.1 Fundamentals Test set-up Evaluation Limits of location References Partial Discharge Measurementson Switchgear Equipments By Dipl.-Ing. G. Luxa Introduction PD measurements and interference voltage measurements on outdoor equipments PD measurements on gas-insulated metal enclosed switchgear Type test Routine test Test procedure according to DIN VDE 0670 Part 8, Sept Test procedure according to proposed DIN VDE 0670 Part 8 A 1, Sept Highest permissible PD magnitude PD measurements on components of metal enclosed SFg-insulated switchgear Effect of partial discharges and results of life-tests PD measurements on switchgear modules during final test at the factory Characteristic PD appearances during test on insulators and modules PD Measurements on Prefabricated Substations On-site By Dipl.-Ing. C. Neumann Introduction Construction and insulation System of prefabricated substations PD-measuring circuit

7 Measuring sensitivity and calibration of the circuit Equivalent circuit of the complete measuring set-up for PD measurement on substations ' Measuring set-ups Conventional unshielded set-up Completely shielded set-up Some fundamentals of shielding technology Example of a completely shielded measuring set-up Measured results and measuring sensitivity Background noise level Transfer characteristic Computer evaluation of the transfer characteristic Detection of PD locations with the help of transfer characteristic Application of narrow-band and wideband PD meters Results of PD measurements on-site Acoustic PD measurement and fault location References Problems of PD Monitoring on Power Transformers in Service By Prof. Dr. H. Borsi Introduction Registering PD characteristics in spatially extended set-ups Registering acoustic characteristics of PD in power transformers Registering and evaluation of electrical characteristics of PD in power transformers on-site Complicating conditions during PD measurements on-site Measures for registering and evaluating PD in power transformers in Service References The Relevance of PD-Diagnosis Tests performed on Medium Voltage enclosed Switchgear subjected to Penetration Tests according to IEC Report 932 By Prof. Dr. D. König and Dipl.-Ing. /. Quint Introduction Indoor switchgear Operating conditions Electrical stressing Penetration and ageing tests Definition of Service conditions and design classes Classification of switchgear Specification of test methods Penetration test

8 Ageing test, Step Ageing test, Step Selection of diagnostic factors and evaluation criteria Ageing Performance of electrically stressed, polluted, polymer support-insulator models References Partial Discharge Test on Low Voltage Components By Dipl.-Ing. A. Bergmann and Dr. Th. Facklam Introduction Judging the insulating capacity of solid insulations Measuring parameters Applicable measuring circuits, test voltage and test frequency Calibration Achievable sensitivity and signal-to-noise ratio PD tests on optocouplers History of the optocoupler PD test experiences on optocouplers Type test on optocouplers with PD measurements Practical experience with PD measurements during production tests PD measurements on isolating transformers PD tests on laminates and coatings Current State of standardisation References Prospect of the Future By Prof. Dr. D. König Critical investigations and consequent improvement of the high frequency transfer Performance of the classical PD-measuring System, especially in the light of the coupling four-terminal device and the amplifier connected in the circuit, as well as increasing their sensitivity Application of digital techniques, storage, data processing and evaluation of PD characteristic parameters Interference suppression especially for PD measurements on-site Further development of unconventional electrical and non-electrical PD-measuring techniques Concluding remarks Reference 306 Author Index 307 Subject Index