REAL-TIME HEALTH MONITORING OF POWER NETWORKS BASED ON HIGH FREQUENCY BEHAVIOR A Dissertation Presented to The Graduate Faculty of The University of Akron In Partial Fulfillment of the Requirements for the Degree Doctor of Philosophy Amir mehdi Pasdar December, 2014 REAL-TIME HEALTH MONITORING OF POWER NETWORKS BASED ON HIGH FREQUENCY BEHAVIOR Amir mehdi Pasdar Dissertation Approved: Accepted: _______________________________ _______________________________ Advisor Department Chair Dr. Yilmaz Sozer Dr. Abbas Omar _______________________________ _______________________________ Committee Member Dean of the College Dr. Malik Elbuluk Dr. George K. Haritos _______________________________ _______________________________ Committee Member Dean of the Graduate School Dr. Tom Hartley Dr. George R. Newkome _______________________________ _______________________________ Committee Member Date Dr. Nathan Ida _______________________________ Committee Member Dr. Ping Yi _______________________________ Committee Member Dr. Alper Buldum ii ABSTRACT Sustainable and reliable electric power delivery to the users is critical for the well being of the society. Electric power delivery can be interrupted due to faults in the transmission lines, which can be defined as the flow of a current through an improper path of the power grid. Faults in the power line could cause power interruption, equipment damage, personal injury or death. Knowledge about the health condition of the power network helps to predict the possibility of the future fault occurrences due to the aging or failure of the insulators, conductors or towers. There has been significant research conducted in the past to monitor the health condition of the power grid, which has resulted in many types of sensors being commercially available. The time domain refletometer (TDR) type sensors have been developed for detecting a fault in an off-line long range power line. Fiber bragg grating (FPG), partial discharge (PD) and Multiple-Displacement-Current (mDCS) type sensors are able to monitor the health condition of the power line in a limited region or substation side of the power grid. Most of the traditional methods are not able to monitor the entire power grid with a resolution of couple miles. There is a need to develop a technique that would scan the entire network despite its widespread and scattered nature with a good resolution. iii This dissertation presents a power grid health monitoring technique based on real time tracking of the grid impedance variation at high frequencies. The impedance of the power grid depends on the geometry and physical conditions of the power line. Since faults have their unique impacts on the power grid impedance, it is possible to investigate the health condition of the power grid through comparison of its current and premeasured impedances at higher frequency range. The proposed technique is applicable for both energized and de-energized power networks in real time. A high frequency signal is injected into the mid-section of the desired line segment while the propagation of the injected signal is blocked at the two ends of the power line segments with the proposed sensor architecture. The impedance of the segment can be determined based on the induced voltage on the line and the current passing through the line. The smart sensor network can detect broken conductor, insulator failure, possible tree fall, human and animal contacts to the power lines or measure the clearance of the power line to hazards. The smart sensor hardware and software are designed, prepared and tested. Different fault scenarios are performed in the sample power line network to validate the capability of the sensor to measure the impedance of the line segment with a reasonable accuracy. iv ACKNOWLEDGEMENTS First and foremost I would like to thank God for giving me the power to believe in myself and pursue my dreams. Next, I wish to express enduring gratitude to my supervisor, Dr. Yilmaz Sozer for his support and advice during these years. I would also like to thank my parents, Mohammad Reza and Soraya, my brother Amir Ali and my grandmother Hamideh for their invaluable love and encouragement over the years. v TABLE OF CONTENTS Page LIST OF FIGURES ....................................................................................................... ix LIST OF TABLES ....................................................................................................... xv CHAPTER I. INTRODUCTION ...................................................................................................... 1 1.1 Transmission .................................................................................................. 2 1.2 Distribution ................................................................................................... 5 1.3 Power Grid Monitoring ................................................................................. 7 1.4 Proposed Approach for Health Monitoring of the Power Grid ................... 13 1.4.1 Layer 1: Health Monitoring of Transmission Line ........................ 15 1.4.2 Layer 2: Distribution and Residential Sides ................................... 18 II. LITERATURE REVIEW AND RESEARCH MOTIVATION .............................. 22 2.1 Introduction ................................................................................................ 22 2.2 Power Grid Monitoring .............................................................................. 22 2.3 Research Motivation ................................................................................... 31 III. OVERHEAD POWER LINE IMPEDANCE MODELLING ............................... 33 3.1 Introduction ................................................................................................ 33 3.2 Previous Works on Overhead Power Line Modeling ................................. 34 3.3 Improved Overhead Power Line Model ..................................................... 39 IV. EFFECT OF LOADS AND FAULTS ON THE LINE IMPEDANCE ................. 44 4.1 Introduction ................................................................................................ 44 vi 4.2 Faults in the Transmission Side of the Grid ..................................................... 44 4.2.1 High voltage insulator .................................................................... 46 4.2.2 Overhead power line core or conductor failure .............................. 58 4.2.3 Overhead power line sagging ......................................................... 65 4.2.4 Overhead power line galloping ...................................................... 69 4.2.5 Objects contacting the line ............................................................. 74 4.3 Home Appliances Impedance ..................................................................... 79 4.4 Summary .................................................................................................... 83 V. FAULT DETECTION AND HEALTH MONITORING FOR TRANSMISSION LINES ...................................................................................................................... 84 5.1 Introduction ................................................................................................ 84 5.2 Sensor Network .......................................................................................... 85 5.3 Smart Sensor ............................................................................................... 88 5.4 Active Line Trapper ................................................................................... 89 5.4.1 Signal matching control algorithm ................................................. 92 5.4.2 Signal matching error ..................................................................... 97 5.5 Fault Detection ........................................................................................... 98 5.6 Optimum Placement of the Smart Sensors ............................................... 101 5.7 Summary .................................................................................................. 102 VI. FAULT DETECTION AND LOCATION FOR DISTRIBUTION LINES ........ 104 6.1 Introduction .............................................................................................. 104 6.2 Low Voltage Distribution ......................................................................... 105 6.2.1 Network Impedance Model at Low Frequency ............................ 106 6.2.2 Network Impedance Model at High Frequency ........................... 107 6.2.3 Response of the network to test signal and fault diagnosis .......... 111 6.2.4 Case study ..................................................................................... 114 vii 6.3 Residential Loads ..................................................................................... 123 6.3.1 Modeling of an individual home appliance impedance ................ 124 6.3.2 Home network impedance ............................................................ 127 6.3.3 Operation status determination of home appliances ..................... 129 6.3.4 Case study ..................................................................................... 132 6.4 Summary .................................................................................................. 138 VII. SMART SENSOR HARDWARE DESIGN AND TEST .................................. 140 7.1 Introduction .............................................................................................