Distributed Fiber Optic Sensing and Dynamic Rating of Power Cables
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SUDHAKAR CHERUKUPALLI, PhD, is a Principal Engineer and Manager in BC Hydro's Transmission Engineering department. He has extensive experience in design, installation, and testing of transmission and distribution cables, and accessories. He has authored and coauthored more than 40 technical publications. He has contributed to several CIGRE Working Groups and the development of many IEEE Standards. In 2016 he received the IEEE-SA Standards Medallion for his contribution to the development of many IEEE Standards. He has been actively interested in Distributed Fiber Sensing since the early 1990s.
GEORGE J. ANDERS, PhD, is president of Anders Consulting Inc. in Toronto. He is also a professor in the Faculty of Electrical and Electronic Engineering of the Technical University of Lodz in Poland. He is the recepient of the 2016 IEEE Herman Halperin Award in Transmission and Distribution and the 2018 IEEE Roy Billinton Award in Power System Reliability.
Content
Preface xiii
Acknowledgments xvi
1 Application of Fiber Optic Sensing 1
1.1 Types of Available FO Sensors 2
1.2 Fiber Optic Applications for Monitoring of Concrete Structures 4
1.3 Application of FO Sensing Systems in Mines 7
1.4 Composite Aircraft Wing Monitoring 8
1.5 Application in the Field of Medicine 9
1.6 Application in the Power Industry 9
1.6.1 Brief Literature Review 10
1.6.2 Monitoring of Strain in the Overhead Conductor of Transmission Lines 15
1.6.3 Temperature Monitoring of Transformers 16
1.6.4 Optical Current Measurements 17
1.7 Application for Oil, Gas, and Transportation Sectors 17
2 Distributed Fiber Optic Sensing 20
2.1 Introduction 20
2.2 Advantages of the Fiber Optic Technology 20
2.3 Disadvantages of the Distributed Sensing Technology 22
2.4 Power Cable Applications 23
3 Distributed Fiber Optic Temperature Sensing 26
3.1 Fundamental Physics of DTS Measurements 26
3.1.1 Rayleigh Scattering 26
3.1.2 Raman Spectroscopy 27
3.1.3 Brillouin Scattering 27
3.1.4 Time and Frequency Domain Reflectometry 30
4 Optical Fibers, Connectors, and Cables 32
4.1 Optical Fibers 32
4.1.1 Construction of the Fiber Optic Cable and Light Propagation Principles 33
4.1.2 Protection and Placement of Optical Fibers in Power Cable Installations 38
4.1.3 Comparison of Multiple and Single-Mode Fibers 44
4.2 Optical Splicing 45
4.3 Fiber Characterization 47
4.4 Standards for Fiber Testing 55
4.4.1 Fiber Optic Testing 56
4.4.2 Fiber Optic Systems and Subsystems 56
4.5 Optical Connectors 68
4.6 Utility Practice for Testing of Optical Fibers 74
4.7 Aging and Maintenance 75
5 Types of Power Cables and Cable with Integrated Fibers 77
5.1 Methods of Incorporating DTS Sensing Optical Fibers (Cables) into Power Transmission Cable Corridors 77
5.1.1 Integration of Optical Cable into Land Power Cables 77
5.1.2 Integration of Optical Cable into Submarine Power Cables 78
5.1.3 Other Types of Constructions 78
5.1.4 Example of Construction of the Stainless Steel Sheathed Fiber Optic Cable 81
5.1.5 Example of a Retrofit Placement of an Optical Cable into 525 kV Submarine SCFF Power Cable Conductor 82
5.1.5.1 Objectives of the Project 82
5.1.5.2 Installation 84
5.2 Advantages and Disadvantages of Different Placement of Optical Fibers in the Cable 87
5.2.1 An Example with Placement of FO Sensors at Different Locations Within the Cable Installation 89
5.3 What are Some of the Manufacturing Challenges? 92
6 DTS Systems 94
6.1 What Constitutes a DTS System? 94
6.2 Interpretation and Application of the Results Displayed by a DTS System 95
6.2.1 General 95
6.2.2 Comparison of Measured and Calculated Temperatures 97
6.3 DTS System Calibrators 100
6.4 Computers 100
6.5 DTS System General Requirements 101
6.5.1 General Requirements 101
6.5.2 Summary of Performance and Operating Requirements 102
6.5.3 Electromagnetic Compatibility Performance Requirements for the Control PC and the DTS Unit 103
6.5.4 Software Requirements for the DTS Control 104
6.5.5 DTS System Documentation 105
7 DTS System Calibrators 106
7.1 Why is Calibration Needed? 106
7.2 How Should One Undertake the Calibration? 107
7.3 Accuracy and Annual Maintenance and Its Impact on the Measurement Accuracy 109
8 DTS System Factory and Site Acceptance Tests 112
8.1 Factory Acceptance Tests 113
8.1.1 Factory QA Tests on the Fiber Optic Cable 113
8.1.2 FIMT Cable Tests 114
8.1.3 Temperature Accuracy Test 115
8.1.4 Temperature Resolution Test 116
8.1.5 Temperature Reading Stability Test 116
8.1.6 Long-Term Temperature Stability Test 116
8.1.7 Transient Response Test 117
8.1.8 Initial Functional Test and Final Inspection 117
8.2 DTS Site Acceptance Tests (SAT) 119
8.2.1 Final Visual Inspection and Verification of Software Functionality 120
8.2.2 Functionality Test on the DTS Unit 120
8.2.3 Verification of the Optical Switch 120
8.2.4 System Control Tests 120
8.2.5 System Integration Test with Control Center (if Applicable) 121
8.3 Typical Example of DTS Site Acceptance Tests 121
8.4 Site QA Tests on the Optical Cable System 125
8.5 Site Acceptance Testing of Brillouin-Based DTS Systems 126
8.6 Testing Standards That Pertain to FO Cables 127
9 How Can Temperature Data Be Used to Forecast Circuit Ratings? 129
9.1 Introduction 129
9.2 Ampacity Limits 129
9.2.1 Steady-State Summer and Winter Ratings 130
9.2.2 Overload Ratings 130
9.2.3 Dynamic Ratings 130
9.3 Calculation of Cable Ratings - A Review 131
9.3.1 Steady-State Conditions 132
9.3.2 Transient Conditions 133
9.3.2.1 Response to a Step Function 134
9.4 Application of a DTS for Rating Calculations 138
9.4.1 Introduction 138
9.4.2 A Review of the Existing Approaches 139
9.4.3 Updating the Unknown Parameters 144
9.5 Prediction of Cable Ratings 146
9.5.1 Load Forecasting Methodology 146
9.6 Software Applications and Tools 148
9.6.1 CYME Real-Time Thermal Rating System 150
9.6.1.1 Verification of the Model 151
9.6.2 EPRI Dynamic Thermal Circuit Rating 154
9.6.3 DRS Software by JPS (Sumitomo Corp) in Japan 156
9.6.4 RTTR Software by LIOS 158
9.7 Implementing an RTTR System 161
9.7.1 Communications with EMS 162
9.7.2 Communications with the Grid Operator 163
9.7.3 IT-Security, Data Flow, Authentication, and Vulnerability Management 163
9.7.4 Remote Access to the RTTR Equipment 164
9.8 Conclusions 164
10 Examples of Application of a DTS System in a Utility Environment 166
10.1 Sensing Cable Placement in Cable Corridors 166
10.2 Installation of the Fiber Optic Cable 167
10.3 Retrofits and a 230 kV SCFF Transmission Application 172
10.3.1 Early 230 kV Cable Temperature Profiling Results 172
10.3.2 Location, Mitigation, and Continued Monitoring of the 230 kV Hot Spots 175
10.4 Example of a DTS Application on 69 kV Cable System 177
10.5 Verification Steps 178
10.5.1 Analytical Methods 179
10.5.2 Dynamic Thermal Circuit Ratings 180
10.6 Challenges and Experience with Installing Optical Fibers on Existing and New Transmission Cables in a Utility Environment 181
11 Use of Distributed Sensing for Strain Measurement and Acousitc Monitoring in Power Cables 185
11.1 Introduction 185
11.2 Strain Measurement 185
11.3 Example of Strain Measurement of a Submarine Power Cable 186
11.3.1 Introduction 186
11.3.2 The Importance of Tight Buffer Cable 187
11.3.3 Description of the Brillouin Optical Time Domain Reflectometer (BOTDR) System for Strain Measurement 188
11.3.4 Experimental Setup 188
11.3.5 Measurement Results 191
11.3.6 Discussion 195
11.4 Calculation of the Cable Stress from the Strain Values 197
11.5 Conclusions from the DSM Tests 198
11.6 Distributed Acoustic Sensing 199
11.7 Potential DAS Applications in the Power Cable Industry 202
11.8 An Example of a DAS Application in the USA 203
11.9 An Example of a DAS Application in Scotland 207
11.10 Conclusions 208
Bibliography 210
Index 216
