Distributed Fiber Optic Sensing and Dynamic Rating of Power Cables

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.

• Preface xiiiAcknowledgments xvi1 Application of Fiber Optic Sensing 11.1 Types of Available FO Sensors 21.2 Fiber Optic Applications for Monitoring of Concrete Structures 41.3 Application of FO Sensing Systems in Mines 71.4 Composite Aircraft Wing Monitoring 81.5 Application in the Field of Medicine 91.6 Application in the Power Industry 91.6.1 Brief Literature Review 101.6.2 Monitoring of Strain in the Overhead Conductor of Transmission Lines 151.6.3 Temperature Monitoring of Transformers 161.6.4 Optical Current Measurements 171.7 Application for Oil, Gas, and Transportation Sectors 172 Distributed Fiber Optic Sensing 202.1 Introduction 202.2 Advantages of the Fiber Optic Technology 202.3 Disadvantages of the Distributed Sensing Technology 222.4 Power Cable Applications 233 Distributed Fiber Optic Temperature Sensing 263.1 Fundamental Physics of DTS Measurements 263.1.1 Rayleigh Scattering 263.1.2 Raman Spectroscopy 273.1.3 Brillouin Scattering 273.1.4 Time and Frequency Domain Reflectometry 304 Optical Fibers, Connectors, and Cables 324.1 Optical Fibers 324.1.1 Construction of the Fiber Optic Cable and Light Propagation Principles 334.1.2 Protection and Placement of Optical Fibers in Power Cable Installations 384.1.3 Comparison of Multiple and Single‐Mode Fibers 444.2 Optical Splicing 454.3 Fiber Characterization 474.4 Standards for Fiber Testing 554.4.1 Fiber Optic Testing 564.4.2 Fiber Optic Systems and Subsystems 564.5 Optical Connectors 684.6 Utility Practice for Testing of Optical Fibers 744.7 Aging and Maintenance 755 Types of Power Cables and Cable with Integrated Fibers 775.1 Methods of Incorporating DTS Sensing Optical Fibers (Cables) into Power Transmission Cable Corridors 775.1.1 Integration of Optical Cable into Land Power Cables 775.1.2 Integration of Optical Cable into Submarine Power Cables 785.1.3 Other Types of Constructions 785.1.4 Example of Construction of the Stainless Steel Sheathed Fiber Optic Cable 815.1.5 Example of a Retrofit Placement of an Optical Cable into 525 kV Submarine SCFF Power Cable Conductor 825.1.5.1 Objectives of the Project 825.1.5.2 Installation 845.2 Advantages and Disadvantages of Different Placement of Optical Fibers in the Cable 875.2.1 An Example with Placement of FO Sensors at Different Locations Within the Cable Installation 895.3 What are Some of the Manufacturing Challenges? 926 DTS Systems 946.1 What Constitutes a DTS System? 946.2 Interpretation and Application of the Results Displayed by a DTS System 956.2.1 General 956.2.2 Comparison of Measured and Calculated Temperatures 976.3 DTS System Calibrators 1006.4 Computers 1006.5 DTS System General Requirements 1016.5.1 General Requirements 1016.5.2 Summary of Performance and Operating Requirements 1026.5.3 Electromagnetic Compatibility Performance Requirements for the Control PC and the DTS Unit 1036.5.4 Software Requirements for the DTS Control 1046.5.5 DTS System Documentation 1057 DTS System Calibrators 1067.1 Why is Calibration Needed? 1067.2 How Should One Undertake the Calibration? 1077.3 Accuracy and Annual Maintenance and Its Impact on the Measurement Accuracy 1098 DTS System Factory and Site Acceptance Tests 1128.1 Factory Acceptance Tests 1138.1.1 Factory QA Tests on the Fiber Optic Cable 1138.1.2 FIMT Cable Tests 1148.1.3 Temperature Accuracy Test 1158.1.4 Temperature Resolution Test 1168.1.5 Temperature Reading Stability Test 1168.1.6 Long‐Term Temperature Stability Test 1168.1.7 Transient Response Test 1178.1.8 Initial Functional Test and Final Inspection 1178.2 DTS Site Acceptance Tests (SAT) 1198.2.1 Final Visual Inspection and Verification of Software Functionality 1208.2.2 Functionality Test on the DTS Unit 1208.2.3 Verification of the Optical Switch 1208.2.4 System Control Tests 1208.2.5 System Integration Test with Control Center (if Applicable) 1218.3 Typical Example of DTS Site Acceptance Tests 1218.4 Site QA Tests on the Optical Cable System 1258.5 Site Acceptance Testing of Brillouin‐Based DTS Systems 1268.6 Testing Standards That Pertain to FO Cables 1279 How Can Temperature Data Be Used to Forecast Circuit Ratings? 1299.1 Introduction 1299.2 Ampacity Limits 1299.2.1 Steady‐State Summer and Winter Ratings 1309.2.2 Overload Ratings 1309.2.3 Dynamic Ratings 1309.3 Calculation of Cable Ratings – A Review 1319.3.1 Steady‐State Conditions 1329.3.2 Transient Conditions 1339.3.2.1 Response to a Step Function 1349.4 Application of a DTS for Rating Calculations 1389.4.1 Introduction 1389.4.2 A Review of the Existing Approaches 1399.4.3 Updating the Unknown Parameters 1449.5 Prediction of Cable Ratings 1469.5.1 Load Forecasting Methodology 1469.6 Software Applications and Tools 1489.6.1 CYME Real‐Time Thermal Rating System 1509.6.1.1 Verification of the Model 1519.6.2 EPRI Dynamic Thermal Circuit Rating 1549.6.3 DRS Software by JPS (Sumitomo Corp) in Japan 1569.6.4 RTTR Software by LIOS 1589.7 Implementing an RTTR System 1619.7.1 Communications with EMS 1629.7.2 Communications with the Grid Operator 1639.7.3 IT‐Security, Data Flow, Authentication, and Vulnerability Management 1639.7.4 Remote Access to the RTTR Equipment 1649.8 Conclusions 16410 Examples of Application of a DTS System in a Utility Environment 16610.1 Sensing Cable Placement in Cable Corridors 16610.2 Installation of the Fiber Optic Cable 16710.3 Retrofits and a 230 kV SCFF Transmission Application 17210.3.1 Early 230 kV Cable Temperature Profiling Results 17210.3.2 Location, Mitigation, and Continued Monitoring of the 230 kV Hot Spots 17510.4 Example of a DTS Application on 69 kV Cable System 17710.5 Verification Steps 17810.5.1 Analytical Methods 17910.5.2 Dynamic Thermal Circuit Ratings 18010.6 Challenges and Experience with Installing Optical Fibers on Existing and New Transmission Cables in a Utility Environment 18111 Use of Distributed Sensing for Strain Measurement and Acousitc Monitoring in Power Cables 18511.1 Introduction 18511.2 Strain Measurement 18511.3 Example of Strain Measurement of a Submarine Power Cable 18611.3.1 Introduction 18611.3.2 The Importance of Tight Buffer Cable 18711.3.3 Description of the Brillouin Optical Time Domain Reflectometer (BOTDR) System for Strain Measurement 18811.3.4 Experimental Setup 18811.3.5 Measurement Results 19111.3.6 Discussion 19511.4 Calculation of the Cable Stress from the Strain Values 19711.5 Conclusions from the DSM Tests 19811.6 Distributed Acoustic Sensing 19911.7 Potential DAS Applications in the Power Cable Industry 20211.8 An Example of a DAS Application in the USA 20311.9 An Example of a DAS Application in Scotland 20711.10 Conclusions 208Bibliography 210Index 216