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Developments in Diagnosis of High Voltage Apparatus Michael Muhr Univ

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1 Developments in Diagnosis of High Voltage Apparatus Michael Muhr Univ
Developments in Diagnosis of High Voltage Apparatus Michael Muhr Univ.-Prof. Dipl.-Ing. Dr.techn. Dr.h.c. Institute of High Voltage Engineering and System Management University of Technology Graz

2 Recording of technical or characteristic values Monitoring
Evaluation of these values Analysis Recognition of the condition and proposal for problem-solving strategies Diagnosis M. Muhr

3 Technical Diagnostics - TD
Science of recognition of the condition of technical systems Aim of TD is to identify, to check and to classify characteristics of the condition of technical systems  to change or to influence the condition of these systems Quality assurance of technical systems Avoidance of an outage of technical systems M. Muhr

4 Technical Diagnostic + Prevent failure + Increase reliability + Economic use of equipment - Costs - Effort - System Optimized usage of diagnostic tools Technique / method Time interval Complexity M. Muhr

5 Availability of technical systems
Condition evaluation Risk evaluation Repair Maintenance Modernization Technical Diagnostics M. Muhr

6 „lifetime extention" by maintenance
Life Cycle Condition load t „lifetime extention" by maintenance pollution ageing critical threshold „normal“ defect failure Lifetime M. Muhr

7 Stress and Ageing Models
M. Muhr

8 Lifetime Estimation of Transformers
M. Muhr

9 Technical Diagnostic Evaluation
M. Muhr

10 Original condition with ageing
Aim of TD Original condition - Monitoring - Analysis - Diagnosis Current condition - Ageing behaviour - Life time - Preventive maintenance - Repair Modernization Original condition with ageing M. Muhr

11 Monitoring of equipment Investigations at equipment and models
Tasks of TD Monitoring of equipment Investigations at equipment and models Characteristic values, current, voltage etc. Life-time behaviour Determining of limits Setting of continuous voltage strength Optimization of life-time Decision - Continuation of operation - Maintenance - Renewing M. Muhr

12 Determination of Early Failures
Bathtub Curve: from statistical analysis Weibull Distribution: d<1: early failure d=1: stochastic process d>1: ageing process M. Muhr

13 Ageing of an electrical insulation system
Ageing stress Thermal Electrical Ambient Mechanical Ageing mechanism Instrinic Exstrinic Single stress Multi stress Electrical insulation system Failure M. Muhr

14 M. Muhr TD at equipment of electrical power engineering
Analytic and spectrometry UV, VIS, IR - Spectrometry Gaschromatography Mass spectrometry Thermal diagnostic Thermovision Temperature measurement Mechanical diagnostic Sound emission analysis Dilatometry Mechanical spectrometry Analysis of mechanical quantities Visual diagnostic UV - Videography Thermography Endoscopy X-ray graphy Dielectric diagnostic Ue u(t) C(f) tan δ(f) Breakdown diagnostic Ud φ (Ud) t (Ud) Partial discharge diagnostic Ue Q (pd) φ (pd) M. Muhr

15 Maintenance Strategies - Lifetime
M. Muhr

16 Blockdiagramm of a Diagnosis System
Excitation Measuring voltage Measuring temperature Reference components Diagnosis sample Original Mode Stress generation Voltage Temperature Vibrations Climate Control Voltage Temperature Data acquisition - Sensors Assessment and control unit Storage of quantities Run-off control Data processing Input and Presentation Further processing Interface M. Muhr

17 Non – Destructive TD at Power Apparatus
Cables Solid switchgears Capacities Transformers Instrument-transformers Rotating machines Insulators Conventional switchgears Circuit breaker Gasinsulated switchgears Dielectric diagnostic Visual TD Pd-diagnostic Sound emission diagnostic Gas analysis TD of mechanical quantities Leakage current diagnostic TD of thermal and mechanical quantities TD of thermal quantities M. Muhr

18 Basis Aspects of TD Aim Technique Method Quantity
Connection between quantity and physical / chemical / technical structure of diagnostic sample Diagnostic criterion - limit M. Muhr

19 Meaningfulness (stress)
Technical Diagnostic Thermal Mechanical Dielectrical Partial Discharge Breakdown Material analytic and Spectrometry Non-destructive individual testing Quasi non-destructive Partly individual testing Destructive Type approval test Random check Meaningfulness (stress) M. Muhr

20 Electrical Diagnostic Methods
Dielectric Breakdown Partial Discharge M. Muhr

21 Dielectric Diagnostics
Observation and evaluation of interaction of electric fields and material Insulation Resistance Capacity and Dissipation Factor Isothermal Relaxation Current Analysis (IRC) Polarisation / Depolarisation Current Analysis (PDC) Frequency Response Analysis (FRA) M. Muhr

22 Insulation Resistance
Guard Ring Arrangement U= I RS RO RD U= I RS RO RD Insulations Resistance Surface Resistance M. Muhr

23 Capacity and Dissipation Factor

24 Analyse in Time Domain M. Muhr V A PDC IRC PDC RVM
Discharge Voltage Analyse Discharge Current Analyse Recovery Voltage Analyse Charging current Analyse 0% 20% 40% 60% 80% 100% 120% PDC IRC PDC RVM current voltage V A Schema M. Muhr

25 Isothermal Relaxation Current Analysis (IRC)
V A Schema M. Muhr

26 Polarisation / Depolarisation Current Analysis (PDC)
Time V A Polarisation Schema Depolarisation M. Muhr

27 Frequency Response Analysis (FRA)
U, I U, I HV LV M. Muhr

28 Breakdown Diagnostic HV-AC M. Muhr

29 Breakdown Test with Insulating Oil
M. Muhr

30 Partial Discharge (PD) Measurement
Sensitive nondestructive method as important diagnostic tool for evaluation of the insulation condition PD-defect Location and Detection Electrical Non electrical methods M. Muhr

31 Partial Discharge Diagnostic
HV Optical IEC 60270 Electrical HF/VHF/UHF Mechanical Acoustic Opto-acoustic Chemical M. Muhr

32 PD-Detection Methods IEC 60270
Conventional electrical measurement Integration at frequency domain Narrow-band Wide-band Integration at time domain G ZFilter HV-Source Test object Coupling capacitor PD-System HV measure PD Pulse Quadripole Measuring impedance M. Muhr

33 PD-Measurement Results
Phase correlated Single impulses Time correlated M. Muhr

34 PDC Analyse M. Muhr

35 Unconventional PD-Detection
Rd ST CC VP W RPA1 HST1 AMP SYNC ICM LWL Signal- conversion acoustic optical Oscilloscope ADU electrical Surface LWL fibre Fibre in oil/board M. Muhr

36 PD-Detection Methods Electrical measurements with high frequencies
HF / VHF method – 3 MHz to 300 MHz UHF method – 300 MHz to 3 GHz Acoustic measurements – 10 kHz to 300 kHz Optical measurements – ultraviolet – visible – infrared range Chemical measurements - Acoustic HV - Chemical - Optical PD Directional microphone M. Muhr

37 HF / VHF – PD-Measurement
cable PD-signal Rogowski coil PD-signal current wire sheath cable inductive PD-signal sheath interruption measurement impedance cable measurement impedance cable HV source PD-signal galvanic M. Muhr

38 HF / VHF – PD-Measurement
Rogowski coil Rogowski coil PD Analyser Measuring for HF – PD-detection on machines, VHF – PD-coupler, Split ring Rogowski coil M. Muhr

39 HF / VHF – PD-Measurement
2 1 3 direct. coupling A B C D impulse source / - No. signal at coupling output A B C D joint /1 X left cable / 2 right cable / 3 Principle of the coupler sensor M. Muhr

40 UHF – PD-Measurement M. Muhr Wide band Narrow band
low-pass filter Peak detector PD measuring instrument PRPD pattern Wide band Narrow band Spectrum analyser amplifiers UHF – PD-measurement M. Muhr

41 Field grading electrodes
UHF – PD-Sensors Conductor Cage Detector Dectector Conductor Cage - Mobile UHF-window sensor Conventional UHF-sensors Disc sensor Cone sensor Field grading electrodes M. Muhr

42 UHF – PD-Fault Location
Schematic arrangement Sensor 1 Pre amplifier Measuring instrument L2 Sensor 2 1 ... Sensor 1 2 ... Sensor 2 Time delay Zeit Amplitude 1 2 Defect M. Muhr

43 Acoustic – PD-Measurement
Acoustic Partial Discharge Detection Acoustic signal as a result of the pressure wave produced by PD Frequency spectrum 10 Hz up to 300 kHz SF6 Box AE Sensor Air Principle schematic to the acoustic PD-detection M. Muhr

44 Acoustic – PD-Sensors - Piezo-electric (sound emission) - Condenser microphones Structure-born sound-resonance - Accelerometer Opto-acoustic-sensor HV Time delay Sensor PD Time Signal Directional microphone PD HV M. Muhr

45 Acoustic – PD-Measurement
PD-Detector AE Sensor Oscilloscope amplifier Filter A/D Converter Acoustic – PD-detection system M. Muhr

46 Opto-Acoustic – PD-Measurement
Laser Reference optical fibre coil Sensing optical fibre coil Oil tank High Voltage PD-source Detector Beam Splitter Experimental setup of the optical interferometric detection of PD M. Muhr

47 PD – Optical Detection M. Muhr Measuring circuit after IEC 60270
Optical fibre with lens Optical fibre Lens Peak Medium oil Observation area Rd PC LWL M ST CC VP PR W IEC 270 optical system Oscilloscope, ADU Signal- conversion Voltage supply Fluorescent optical fibre conventional opt. fibre Peak fluorescent Plate Measuring circuit after IEC 60270 and optical measuring system M. Muhr

48 Optical – PD-Detection in GIS
SF6 Photomultiplier Conv. PD Detector ADU I/U Oscilloscope Emission spectrum of corona discharges in SF6 Test arrangement for optical PD-measurement M. Muhr

49 Optical – PD-Measurement
Operation diagram camera DayCor IITM and application M. Muhr

50 Electrical PD – Application Optical Acoustic Chemical HF / VHF UHF
GIS Overhead lines Acoustic - High voltage cables GIS Transformers Overhead lines Chemical GIS Transformer Machines PD – Application Electrical Transformers GIS Machines Overhead lines ... HF / VHF - High voltage cables - Transformers UHF - GIS - GIL - Transformer monitoring M. Muhr

51 Monitoring, Data Processing, Announcement
Data input and monitoring unit Report Display Data archiving Real time announcement Alarm Data transfer Trend analysis Modem Telephone lines PC station M. Muhr

52 Example for signal processing
Pattern Recognition Signal processing Report Display Data store Data transfer Trend analysis Example for signal processing M. Muhr

53 Power Transformer Diagnostics
IEC 599 IEEE C Furane Values Dörnenburg Moisture Dissolved Gas Analyses (DGA) Rogers Neutralization Value Duval Oil Analysis Other Methods Fibre Optics Chemical Loss Factor Endoscopy Oil Analysis Eye Breakdown Voltage Optical UHF PD-Detection Electrical Partial Discharges PD-Evaluation Acoustics Elektrisch DAC-PD-Measurement Mechanical Operating Noises Mechanisch PD Location Insulation Dynamics Thermal Loss Factor Thermisch PDC-Analysis Transient Oil Pressure Insulation Resistance Operating Temperature Signal Analysis Oil Stream RVM, FDS Analysis Thermography FRA-Analysis Temperature Monitoring Transfer Function Wavelet Technique M. Muhr

54 M. Muhr Method Information Comment Oil analysis OA
Oil ageing, insulation property Routine Gas-in-oil analysis DGA Oil and paper ageing, flashovers, PD, hot spots Loss factor (Dielectric dissipation factor) tanδ Dielectric losses in the insulation system Furane values FA Ageing of the paper insulation Condition determination Degree of polymerization DP Partial discharges PD Paper ageing, ageing of the insulation system Polarisation and depolarisation currents PDC Water content in the paper insulation Infrared measurements IR Overload, failure of the cooling system Condition determination and for fault location Acoustic  AM PD-detection and location For fault location Frequency response FRA Mechanical condition of the windings After short circuits M. Muhr

55 Oil Analysis Moisture Karl-Fischer titration Capacitive sensors
Water content in oil Water content in paper Temperature High Low Moisture Karl-Fischer titration Capacitive sensors Breakdown voltage PDC Breakdown voltage [kV] Water content [ppm] dilution emulsion M. Muhr

56 Oil Analysis Loss Factor (tanδ) Heat losses are temperature-dependent
High loss factor – thermal breakdown Limit: tanδ ≤ 5 % by T=100° C Temperature dependace of tanδ for new oil (1) and oils in operation (2,3,4) M. Muhr

57 Oil Analysis Dissolved Gas Analysis (DGA)
Key gases: hydrogen, methane, ethane, ethylene, acetylene, propane, propylene, carbon monoxide, carbon dioxide Detectable failures: thermal and electrical failure M. Muhr

58 Oil Analysis Duval triangel DGA - Evaluation CIGRE IEC IEEE Dörnenburg
MSS / VDE-Diagnosis Rogers Duval Laborelec KEPCO Duval triangel M. Muhr

59 Paper Analysis Polymerisation degree (DP)
In direct correlation with the mechanical strength new paper DP 1000 – 1200 paper at the end of life time DP approx.200 A decrease in the DP value furane is going hand in hand with an increase of components Furane dependence Oil temperature Type of oil Neutralization factor Type of paper Sludge content Moisture content of oil and paper Ratio oil / paper M. Muhr

60 Oil Analysis Furane Analysis
Condition of paper insulation (mechanical strength) determined by degree of polymerization High performance liquid chromatograph (HPLC) M. Muhr

61 Measurement in laboratory
Partial Discharges Conventional Acoustic Optical Chemical Electrical New Systems: electromagnetic wave detection, transfer functions, damped AC voltage (DAC) Measurement in laboratory conventional measurement IEC 60270 Acoustic PD - measurement Optical PD - measurement Chemical PD – measurement (DGA) electrical High frequency PD - measurement Narrow band Δf ~ 10 kHz Broadband Δf ~ kHz HF/UHF method f ~ kHz Narrow band Δf < 2 MHz Measurement on-site UHF method f ~ 0,2 - 2 GHz Broadband Δf > 50 MHz M. Muhr

62 Charging and discharging measurements
Dielectric Diagnosis Charging and discharging measurements M. Muhr

63 Diagnostics with Transient Test Voltages
Frequency response analysis (FRA) and transfer function Low voltage impulse response (LVI) Wavelet analyse DAC-PD-measurement FRA M. Muhr

64 Thermal and Optical Diagnostic Methods
Thermography Temperature measurement with fibre optics PT-100 elements Surface acoustic wave radio transponder Visual inspection Endoscopy Ocular OKULAR Light source LICHTQUELLE Flexible end FLEXIBLES ENDE Field of vision BLICKBEREICH M. Muhr

65 Mechanical Diagnostic Methods
Transient oil pressure (short circuit) Stream analysis (oil and cooling air) Acoustic PD-locating Stream No stream M. Muhr

66 Diagnosis of Rotating Machines
Tasks Thermal monitoring Air cooling analysis Monitoring of vibrations Acoustic monitoring Chemical-analytic monitoring Magnetic monitoring Electrical monitoring M. Muhr

67 Rotating Machines Electrical Diagnosis Methods
Impulse voltage test at windings Attenuation factor Resonance frequency of resonating circuit - Oscillogram of a decaying oscillation Error –free faulty M. Muhr

68 Rotating Machines Dielectric Diagnosis Time domain
Insulation resistance Riso Insulation current iiso = f (t) Frequency domain Capacitance Loss factor tan d = f (w), C, U M. Muhr

69 Rotating Machines Dielectric Diagnosis
Insulation time constant t10 as criterion for the dryness limit curve t10 = Riso (600s) x C (50Hz) t10 = f (d) Dry condition Humid condition Dryness limit curve Cooling Heating Insulation time constant in dependance of the slot temperature and the insulation condition M. Muhr

70 Rotating Machines Partial discharge (Pd) diagnosis Pd’s
In cavities of solid insulation In the are of the end winding At no-perfect working protect system of mica At vibrating parts of winding M. Muhr

71 Physical Condition of Windings
M. Muhr

72 Discharge behaviour within Machine Windings
M. Muhr

73 Thermography as Diagnostic Tool
Requirement Increasing efficiency of power grid Decreasing of inspection and maintenance rate Load situation Increasing electrical power consumption Higher loads on equipment Demand of ON-line diagnostic tools E.g. Contact less temperature measurement M. Muhr

74 Thermography as Diagnostic Tool
Material/Structure Heat Generation Temperature Surface temperature power output Surrounding Load current Resistor Voltage Conductivity Dielectric losses Temperature measurement M. Muhr

75 Temperature Measurement
High Voltage Object Temperature Sensor Coupling Signalling Transmission power supply Isolated Transmission Isolated Coupling High Voltage Object Temperature Sensor Coupling Signalling Transmission power supply M. Muhr

76 Spot Temperature Measurement
29.8°C 29.7°C 29.6°C 29.9°C 29.5°C 30.0°C 30.1°C Transformer M. Muhr

77 Temperature Distribution
33°C 23°C Hot Cold M. Muhr

78 Thermography in HV - Systems
Applications Connections Switches Power transformers Measuring transformers Overhead lines Cable terminations Bushings Fuses Rotating Machines M. Muhr

79 Applications of Thermography
Poor contact resistance of a joint Poor contact resistance of a disconnector M. Muhr

80 Applications of Thermography
Compression connector of an overhead line Asymmetrical energy flow of a cable M. Muhr

81 Applications of Thermography
Bearing, machines © FLIR Slip-ring brushes M. Muhr

82 Thank You for Your Attention
M. Muhr

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