Practical Partial Discharge Measurement on Electrical Equipment

Cover
Title Page
Copyright Page
Dedication
Contents
About the Authors
Preface
Acknowledgments
Acronyms
Chapter 1 Introduction
	1.1 Why Perform Partial Discharge Measurements?
	1.2 Partial Discharge and Corona
	1.3 Categories of PD Tests
		1.3.1 Factory PD Testing
		1.3.2 Onsite/Offline PD Tests
		1.3.3 Online PD Testing and Continuous Monitoring
	1.4 PD Test Standards
	1.5 History of PD Measurement
		1.5.1 RIV Test – The First Era
		1.5.2 Analog PD Detection Using Oscilloscopes – The Second Era
		1.5.3 Digitizing, Ultrahigh Frequency, and Post-Processing – The Third Era
	1.6 The Future
	1.7 Roadmap for the Book
	References*
Chapter 2 Electric Fields and Electrical Breakdown
	2.1 Electric Fields in High-Voltage Equipment
		2.1.1 Impact of Electric Field on Partial Discharges
		2.1.2 Basic Quantities and Equations
		2.1.3 Simple Electrode Configurations
		2.1.4 Multi-Dielectric Systems
		2.1.5 Floating Metal Objects
	2.2 Electrical Breakdown
	2.3 Breakdown in Gases
		2.3.1 Breakdown in Uniform Fields
		2.3.2 Breakdown in Divergent Fields
		2.3.3 Breakdown Under Impulse Voltages – the V-t Characteristic
	2.4 Breakdown in Solids
		2.4.1 Electrical Treeing
	2.5 Breakdown in Liquids
	2.6 Dielectric Strength
	References
Chapter 3 Physics of Partial Discharge
	3.1 Introduction
	3.2 Classification of Partial Discharges
	3.3 PD Current Pulse Characteristics
	3.4 Effects of PD
	3.5 Corona Due to Non-Uniform Electric Fields Around Conductors
		3.5.1 PD and Corona Polarity
		3.5.2 Corona AC Phase Position
		3.5.3 Corona Current Pulse Characteristics
	3.6 Partial Discharge in Voids
		3.6.1 PD Inception
		3.6.2 Modified Field Due to Space Charge
	3.7 PD on Insulation Surfaces
		3.7.1 Triple Point Junction
		3.7.2 Electrical Tracking
	3.8 Effect of Ambient Conditions and Conditioning
		3.8.1 Conditioning
		3.8.2 Ambient/Operating Conditions
	3.9 Summary of Measured PD Quantities
		3.9.1 Magnitude
		3.9.2 Pulse Count Rate
		3.9.3 Phase Position
	3.10 Understanding the PD Pattern with Respect to the AC Cycle
		3.10.1 Polarity Analysis
		3.10.2 Physical Basis for PRPD Patterns
		3.10.3 PD Packets
	References
Chapter 4 Other Discharge Phenomena
	4.1 Introduction
	4.2 PD as Interference
	4.3 Circuit Breaker Arcing
	4.4 Contact Arcing and Intermittent Connections
	4.5 Metal Oxide Layer Breakdown
	4.6 Dry Band Arcing
	4.7 Glow (or Pulseless) Discharge
	References
Chapter 5 PD Measurement Overview
	5.1 Introduction
	5.2 Charge-Based and Electromagnetic Measurement Methods
	5.3 Optical PD Detection
	5.4 Acoustic Detection of PD
		5.4.1 Acoustic Detection of PD Through the Air
		5.4.2 Acoustic PD Detection Within Enclosed HV Apparatus
	5.5 Chemical Detection
		5.5.1 Ozone in Air
		5.5.2 Dissolved Gas Analysis (DGA)
		5.5.3 SF6 Decomposition Products in GIS
	References
Chapter 6 Charge-Based PD Detection
	6.1 Introduction
	6.2 Basic Electrical Detection Circuits Using Coupling Capacitors
		6.2.1 Direct Circuit
		6.2.2 Indirect Circuit
	6.3 Measuring Impedances
		6.3.1 Resistors and Quadripoles
		6.3.2 AC Synchronization and Quadripoles
		6.3.3 High-Frequency Current Transformers
	6.4 Electrical PD Detection Models
		6.4.1 ABC Model
		6.4.2 Dipole Model
		6.4.3 Comparing the ABC Model with the Dipole Model
		6.4.4 Pulse Polarity
	6.5 Quasi-integration in Charge-Based Measuring Systems
		6.5.1 Quasi-integration Explained
		6.5.2 Frequency Range of Charge-Based PD Detectors
	6.6 Calibration into Apparent Charge
		6.6.1 Capacitive Test Objects
		6.6.2 Distributed Test Objects
		6.6.3 Inductive-Capacitive Test Objects
		6.6.4 Practical Calibrators
	References
Chapter 7 Electromagnetic (RF) PD Detection
	7.1 Why Measure Electromagnetic Signals from PD
	7.2 Terminology
	7.3 Basic Electrical Detection Circuits
		7.3.1 Transmission Path
		7.3.2 Sensors
		7.3.3 Time and Frequency Domain Measurement
	7.4 Types of RF Sensors
		7.4.1 Ferrite Antennas
		7.4.2 Magnetic Loops
		7.4.3 Transient Earth Voltage (TEV) Sensors
		7.4.4 Internal or Tank-Mounted UHF Sensors
		7.4.5 Antennas
	7.5 Measuring Instruments
	7.6 Performance and Sensitivity Check
	7.7 PD Source Location
	References
Chapter 8 PD Measurement System Instrumentation and Software
	8.1 Introduction
	8.2 Frequency Range Selection
	8.3 PD Detector Hardware Configurations
		8.3.1 Minimum Threshold and Processing Time
		8.3.2 AC Voltage Measurement and Synchronization
		8.3.3 Combined Analog–Digital Systems
		8.3.4 Digital System to Measure Pulse Magnitude and Selected Pulse Characteristics
		8.3.5 Systems to Facilitate Waveform Post-Processing
	8.4 Hardware-Based Interference Suppression and PD Source Identification
		8.4.1 Hardware-Based Gating
		8.4.2 Time-of-Flight (or Time of Arrival) Method
		8.4.3 Pulse Shape Analysis
	8.5 PD Calibrator Hardware
	8.6 Special Hardware Requirements for Continuous Monitors
		8.6.1 Sensor Reliability
		8.6.2 Instrument Robustness
		8.6.3 Cybersecurity
	8.7 PD System Output Charts
		8.7.1 Pulse Magnitude Analysis (PMA) Plot
		8.7.2 Phase-Magnitude-Number (Ø-q-n) Plot
		8.7.3 Phase-Resolved PD (PRPD) Plot
		8.7.4 Trend Plot
		8.7.5 PDIV/PDEV Plot
		8.7.6 Scatter Plot
	8.8 PD Activity Indicators
		8.8.1 Quasi-Peak PD Magnitude (QIEC)
		8.8.2 Peak PD Magnitude (Qm)
		8.8.3 Integrated PD Indicators
	8.9 Post-Processing Software for Interference Suppression and PD Analysis
		8.9.1 Statistical Post-Processing
		8.9.2 Time-Frequency Maps
		8.9.3 Three-Phase Synchronous Pattern Analysis
		8.9.4 Software-Based Censoring
		8.9.5 Artificial Intelligence (AI) and Expert Systems
	References
Chapter 9 Suppression of External Electrical Interference
	9.1 Impact of External Electrical Interference
		9.1.1 Factory Testing
		9.1.2 Condition Assessment Testing
	9.2 Typical Sources of Noise and External Electrical Interference
		9.2.1 Electrical/Electronic Noise
		9.2.2 External Electrical Interference (“Disturbances”)
	9.3 Interference Suppression for Offline PD Testing
		9.3.1 Electromagnetic Shielded Rooms
		9.3.2 Good Practice for Test Set-Up
		9.3.3 Power Supply Filtering
		9.3.4 Signal Filtering
		9.3.5 PD Measurement Bridges
		9.3.6 Time-of-Flight
		9.3.7 PRPD Pattern Recognition
		9.3.8 Time-Frequency Map
		9.3.9 Gating
	9.4 Online Interference Suppression
	References
Chapter 10 Performing PD Tests and Basic Interpretation
	10.1 Introduction
	10.2 PDIV/PDEV Measurement
		10.2.1 Test Procedure
		10.2.2 Sensitivity
		10.2.3 Interpretation
	10.3 PD Magnitude and PRPD Test Procedure
		10.3.1 Offline Testing
		10.3.2 Online Testing
		10.3.3 Differences Between Offline and Online Tests
		10.3.4 Conditioning in Offline Tests
	10.4 Interpretation of PD Magnitude
		10.4.1 Trend Over Time
		10.4.2 High PD Level
		10.4.3 PD Polarity Effect
		10.4.4 Other PD Activity Indicators
	10.5 PRPD Pattern Interpretation
		10.5.1 Phase-to-Ground Patterns
		10.5.2 Generalized Phase-to-Ground PRPD Patterns
		10.5.3 “Rabbit-Ear” Pattern
		10.5.4 Phase-to-Phase PD in Online Tests
		10.5.5 Cross-Coupled Signals Between Phases in Online Tests
		10.5.6 Simultaneous Occurrence of Multiple Aging processes
	10.6 PD Root Cause Identification Using Changes in Ambient and Operating Conditions
	References
Chapter 11 PD Testing of Lumped Capacitive Test Objects
	11.1 Lumped Capacitive Objects
	11.2 Test Procedures
	11.3 Measures to Suppress Electrical Interference
	11.4 Sensitivity Check
	References
Chapter 12 PD in Power Cables
	12.1 Introduction
	12.2 Cable System Structure
		12.2.1 Cable Insulation
		12.2.2 Accessories
	12.3 Cable System Failure Mechanisms
		12.3.1 Extruded Cable Manufacturing Defects
		12.3.2 Aging of Polymeric Cables in Service
		12.3.3 Water Trees
		12.3.4 Aging of Mass-Impregnated Cable
		12.3.5 Joint and Termination Problems
	12.4 Cable PD Test Standards
	12.5 PD Test Sensors
		12.5.1 Capacitive Couplers
		12.5.2 HFCTs on Neutral Grounding Leads
		12.5.3 Imbedded Capacitive Coupler
		12.5.4 Other Sensors
	12.6 PD Pulse Propagation and Detector Bandwidth
	12.7 Factory Quality Assurance (QA) Testing of Power Cable
	12.8 Energizing Cables in Offline/Onsite PD Tests
		12.8.1 Resonant Test Set
		12.8.2 Very Low Frequency (VLF) Systems
		12.8.3 Oscillating Waves Test Set
	12.9 Offline/Onsite Testing
		12.9.1 PD Detection
		12.9.2 Calibration vs Sensitivity Check
		12.9.3 Test Performance
	12.10 Pros and Cons of Offline Versus Online PD Measurements for Condition Assessment
	12.11 Online Monitoring
	12.12 Interference Separation
	12.13 PRPD Patterns
	12.14 PD Source Localization
		12.14.1 Time-Domain Reflectometry
		12.14.2 Time of Arrival
		12.14.3 Amplitude–Frequency (AF) Mapping
	References
Chapter 13 Gas-Insulated Switchgear (GIS)
	13.1 Introduction
	13.2 Relevant Standards and Technical Guidance
	13.3 The GIS Insulation System
		13.3.1 Insulation System Components
		13.3.2 PD Suppression Coatings
		13.3.3 Insulating Gas (SF6 and Alternative Gases)
	13.4 Typical PD Sources in GIS and their Failure Modes
		13.4.1 Mobile Particles
		13.4.2 Floating Potential Discharge
		13.4.3 Protrusions (Inner Conductor or Enclosure)
		13.4.4 Partial Discharges on Insulator Surfaces
		13.4.5 Voids, Cracks, Delamination of Solid Insulators
	13.5 Detection of PD in GIS
	13.6 Charge-Based PD Measurement in GIS
		13.6.1 Charge Calibration
	13.7 Application of Acoustic Techniques for PD Measurement on GIS
	13.8 Radio-Frequency PD Measurement on GIS: The UHF Method
		13.8.1 UHF Sensors
		13.8.2 The RF Signal Propagation Environment in GIS
		13.8.3 The CIGRE Sensitivity Verification
		13.8.4 UHF PD Signal Acquisition: Narrowband vs Wide Band
		13.8.5 Narrowband UHF PD Detection with RF Spectrum Analyzers
		13.8.6 Broadband UHF PD Detection and Measurement
	13.9 GIS Routine Factory Test
	13.10 Onsite PD Measurement of GIS
		13.10.1 High-Voltage Resonant Test-Set for Onsite/Offline Testing
		13.10.2 Problems with Applying IEC 60270 PD Method Onsite
		13.10.3 Applying the UHF Method for Onsite/Offline PD Measurement
		13.10.4 Interference Encountered During Onsite UHF PD Measurement
		13.10.5 UHF PD Source Location: The Time-of-Flight (TOF) Technique
	13.11 Online Continuous PD Monitoring (PDM) of GIS
		13.11.1 Typical GIS PDM System Components
		13.11.2 GIS PDM System Alarm Triggering
		13.11.3 The GIS PDM System False Alarm Problem
		13.11.4 Real-World Application of GIS PDM Systems
		13.11.5 Do I Really Need a PDM System?
	13.12 GIS PD Signal Examples and PRPD Patterns
		13.12.1 Moving Particles
		13.12.2 Floating Potential Discharges
		13.12.3 Protrusions
		13.12.4 Surface Discharges
		13.12.5 Voids, Delamination
		13.12.6 External Interference (EMI, RFI)
	13.13 HVDC GIS: Special Considerations
		13.13.1 PD Defect Characteristics Under HVDC
	References
Chapter 14 Air-Insulated Switchgear and Isolated Phase Bus
	14.1 Introduction
	14.2 AIS Insulation Systems
	14.3 Insulation Failure Processes
		14.3.1 Surface Electrical Tracking
		14.3.2 Air Gap PD
		14.3.3 PD in Cast Epoxy Components
		14.3.4 PD in Cable Accessories
	14.4 PD Sensors
		14.4.1 TEV Sensor
		14.4.2 Capacitive and HFCT Sensors
		14.4.3 RF Antenna
		14.4.4 Ultrasonic Sensors
	14.5 Commissioning and Offline/Onsite Testing
	14.6 Online PD Monitoring
		14.6.1 Systems with Sensors Within the Switchgear
		14.6.2 Systems with Sensors Mounted Outside the Switchgear
	14.7 PD Interpretation for AIS
	14.8 PD Measurement in Isolated Phase Bus
		14.8.1 IPB Deterioration Processes
		14.8.2 Offline PD Tests
		14.8.3 Online PD Monitoring
		14.8.4 Interpretation
	References
Chapter 15 Power Transformers
	15.1 Introduction
	15.2 Transformer Insulation Systems
		15.2.1 Dry-Type Transformer
		15.2.2 Materials Used in Liquid-Filled Paper-Insulated Power Transformers
		15.2.3 Typical Construction Arrangement in Oil-Filled Transformers
	15.3 Typical Causes of PD in Dry-Type (Cast Resin) Transformers
	15.4 Typical Causes of PD in Oil-Filled Transformers
		15.4.1 Defects in Solid Insulating Materials
		15.4.2 Defects in the Core Structure
		15.4.3 Defects Arising During Factory Assembly
		15.4.4 Defects Arising During Onsite Assembly
		15.4.5 PD Caused by Aging During Operation
		15.4.6 Partial Discharges Due to a Poor Electrical Design
	15.5 Relevant Standards
		15.5.1 IEC 60270
		15.5.2 IEC 62478
		15.5.3 IEC 60076-3
		15.5.4 IEC 60076-11
		15.5.5 IEEE C57.12.90
		15.5.6 IEEE C57.113 and C57.124
		15.5.7 IEEE C57.127
	15.6 PD Pulse Propagation and PD Detection in Transformers
		15.6.1 PD Current Pulse Propagation Through Stray Capacitance
		15.6.2 UHF Propagation
		15.6.3 Acoustic Propagation
	15.7 Sensors for PD Detection
		15.7.1 Impedance Connected to Bushing Tap
		15.7.2 Coupling Capacitors
		15.7.3 HFCTs
		15.7.4 VHF/UHF Sensors
		15.7.5 Acoustic Sensor
		15.7.6 Nonelectric Sensors: Laboratory DGA and Online DGA
	15.8 AC Supply for Offline Testing
		15.8.1 Motor-Generator Test Sets
		15.8.2 Electronic Variable AC Supplies
	15.9 Precautions Against Background Noise and Interference in Electrical PD Testing
		15.9.1 Test Site Arrangement
		15.9.2 AC Supply Interference
		15.9.3 Measurement System Arrangement
		15.9.4 Instrument-Based Noise and Interference Separation
	15.10 Factory Acceptance Testing of Transformers
		15.10.1 Conventional IEC 60270 Charge-Based Measurement
		15.10.2 Test Procedure
		15.10.3 Factory Test Pass/Fail Criteria
	15.11 Onsite Offline Testing
		15.11.1 When Onsite Tests Would Be Helpful
		15.11.2 Scope and Aim of an Onsite/Offline Test
		15.11.3 HV Supply Systems
		15.11.4 Typical Onsite Test Procedures
		15.11.5 Acoustic Investigations
	15.12 Online PD Monitoring
		15.12.1 When Online PD Monitoring Would Be Helpful
		15.12.2 Interactions with Other Online Monitoring Systems
		15.12.3 Features of an Online PD Monitoring System
		15.12.4 Suppressing Interferences
		15.12.5 PDM Implementation
		15.12.6 Basic Interpretation of PDM Results
	15.13 Typical PRPD Patterns
		15.13.1 PRPD Pattern Related to Defects in Solid Insulating Materials
		15.13.2 PRPD Pattern Related to Defects in the Core Structure
		15.13.3 Floating Discharge Due to Unbonded Bushing
		15.13.4 PRPD Pattern Due to Trapped Air Within the Transformer After Oil Filling
		15.13.5 PRPD Related to Probable Humidity in Paper Tapes
		15.13.6 PRPD Related to Turn-to-Turn PD
	References
Chapter 16 Rotating Machine Stator Windings
	16.1 Introduction
	16.2 Relevant Standards
	16.3 Stator Winding Insulation Systems
		16.3.1 Insulation System Components
		16.3.2 PD Suppression Coatings
		16.3.3 Stator Winding Construction
	16.4 Stator Winding Insulation Failure Processes
		16.4.1 Poor Epoxy Impregnation
		16.4.2 Inadequate PD Suppression Coatings
		16.4.3 Loose Coils in the Stator Slots
		16.4.4 Inadequate Separation of Coils and Bars in the Endwinding
		16.4.5 Thermal Aging
		16.4.6 Thermo-Mechanical Aging
		16.4.7 Winding Contamination
		16.4.8 Metallic Debris
	16.5 PD Pulse Propagation in Stator Windings
		16.5.1 Propagation Models
		16.5.2 Experimental Findings
		16.5.3 Impact of Coil Voltage on PD Signal
	16.6 PD Sensors
		16.6.1 Sensors for Offline Testing
		16.6.2 Sensors for Online Testing
	16.7 Factory Acceptance Testing
		16.7.1 LF Charge-Based Test Procedures
		16.7.2 HF and VHF Methods
	16.8 Onsite Offline Tests
	16.9 Online Testing and Monitoring
		16.9.1 Sources of Interference
		16.9.2 Periodic Testing vs Continuous Monitoring
		16.9.3 Common Testing/Monitoring Systems
	16.10 Differences Between Online and Offline Tests
	16.11 Interpretation
		16.11.1 Trend Over Time
		16.11.2 Comparison to Similar Machines
		16.11.3 Prediction of Remaining Winding Life
	16.12 Root Cause Identification
		16.12.1 PRPD Pattern Analysis
		16.12.2 Effect of Operating Conditions on PD
		16.12.3 Interpretation Overview for Online PD Tests
	16.13 Locating PD Sites
		16.13.1 Corona/Sniffer Probes
	References
Chapter 17 PD Detection in DC Equipment
	17.1 Why Is HVDC So Popular Now?
	17.2 Insulation System Design in DC
	17.3 The Reasons for PD Testing Using DC
	17.4 Offline PD Testing with DC Excitation
	17.5 Interpretation of PD Measurements Under DC Excitation
		17.5.1 Time Series Interpretation
		17.5.2 Magnitude Dispersion
		17.5.3 Effect of Operating Conditions on PD
	17.6 Perspective
	References
Chapter 18 PD Detection Under Impulse Voltage
	18.1 Introduction
	18.2 Insulation Failure Due to Short Risetime Impulse Voltages
		18.2.1 High Peak Voltage
		18.2.2 Short Risetime Causing High Turn Voltages in Windings
		18.2.3 Overheating of the Stress Relief Coatings
	18.3 Electrical PD Detection
		18.3.1 Directional Electromagnetic Couplers
		18.3.2 VHF and UHF Antennas
		18.3.3 Capacitive Couplers
		18.3.4 HFCT PD Sensors
	18.4 Nonelectrical Sensors
	18.5 PD Display and Quantities Measured
		18.5.1 PD Synchronized to the Voltage Impulse
		18.5.2 PD Synchronized to the Fundamental Frequency AC (PRPD)
		18.5.3 PD Magnitude
		18.5.4 RPDIV and RPDEV
	18.6 Sensitivity and Interference Check
	18.7 Test Procedures
		18.7.1 Offline Tests
		18.7.2 Online Tests
	18.8 Interpretation
		18.8.1 Type I (PD-Free) Insulation Systems
		18.8.2 Type II Insulation Systems
	References
Index
EULA