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Summary
Summary
An advanced level examination of the latest developments in power transformer protection
This book addresses the technical challenges of transformer malfunction analysis as well as protection. One of the current research directions is the malfunction mechanism analysis due to nonlinearity of transformer core and comprehensive countermeasures on improving the performance of transformer differential protection. Here, the authors summarize their research outcomes and present a set of recent research advances in the electromagnetic transient analysis, the application on power transformer protections, and present a more systematic investigation and review in this field. This research area is still progressing, especially with the fast development of Smart Grid. This book is an important addition to the literature and will enhance significant advancement in research. It is a good reference book for researchers in power transformer protection research and a good text book for graduate and undergraduate students in electrical engineering.
Chapter headings include : Transformer differential protection principle and existing problem analysis; Malfunction mechanism analysis due to nonlinearity of transformer core; Novel analysis tools on operating characteristics of Transformer differential protection; Novel magnetizing inrush identification schemes; Comprehensive countermeasures on improving the performance of transformer differential protection
An advanced level examination of the latest developments in power transformer protection Presents a new and systematic view of power transformer protection, enabling readers to design new models and consider fresher design approaches Offers a set of approaches to optimize the power system from a microeconomic point of viewAuthor Notes
Xiangning Lin , Professor, College of Electrical and Electronic Engineering, Huazhong University of Science and Technology, China.
Prof. Lin was the first to discover the ultra-saturation phenomenon of power transformer and he designed operating characteristics analysis planes to make clear the advantages and disadvantages of existing differential protection of power transformer. He invented a variety of novel protection algorithms for the main protection of the power transformer. A series of papers were published in journals including IEEE Transactions on Power Systems and IEEE Transactions on Power Delivery. The work has been widely acknowledged and cited by international peers. He also pioneers the introduction of modern signal processing techniques to design the protection criteria for power transformer. He was the winner of the 2nd Class National Natural Science Award in 2009. He has published nearly 200 papers and books (in Chinese), he also owns over 15 patents.
Jing Ma , Associate Professor, School of Electrical and Electronic Engineering, North China Electric Power University, Beijing, China.
Prof. Ma was the first to apply the two-terminal network algorithm to the areas of power system protection. The work has been widely acknowledged and cited by international peers. He also proposed an approach based on grille fractal to solve the TA saturation problem, and the related paper has been published in the IEEE Transactions on Power Delivery. The research results were used in many practical engineering projects.
Dr. Qing Tian , Senior Engineer with the Maintenance and Test Center of EHV Transmission Co. Ltd, Southern Power Grid, Guangzhou, China.
Dr. Hanli Weng , Senior Engineer with Three-Gorge Hydropower Plant, China Yangtze Power Co., Ltd.
Both have been working in this area since 1995. Their main research fields include power system operation analysis and control, voltage and reactive power optimization, power system reliability and risk assessment and power system energy saving assessment and planning.
Table of Contents
About the Authors | p. xi |
Preface | p. xi |
1 Principles of Transformer Differential Protection and Existing Problem Analysis | p. 1 |
1.1 Introduction | p. 1 |
1.2 Fundamentals of Transformer Differential Protection | p. 2 |
1.2.1 Transformer Faults | p. 2 |
1.2.2 Differential Protection of Transformers | p. 3 |
1.2.3 The Unbalanced Current and Measures to Eliminate Its Effect | p. 5 |
1.3 Some Problems with Power Transformer Main Protection | p. 7 |
1.3.1 Other Types of Power Transformer Differential Protections | p. 7 |
1.3.2 Research on Novel Protection Principles | p. 9 |
1.4 Analysis of Electromagnetic Transients and Adaptability of Second Harmonic Restraint Based Differential Protection of a UHV Power Transformer | p. 17 |
1.4.1 Modelling of the UHV Power Transformer | p. 17 |
1.4.2 Simulation and Analysis | p. 20 |
1.5 Study on Comparisons among Some Waveform Symmetry Principle Based Transformer Differential Protection | p. 27 |
1.5.1 The Comparison and Analysis of Several Kinds of Symmetrical Waveform Theories | p. 27 |
1.5.2 The Theory of Waveform Symmetry of Derivatives of Current and Its Analysis | p. 28 |
1.5.3 Principle and Analysis of the waveform Correlation Method | p. 32 |
1.5.4 Analysis of Reliability and Sensitivity of Several Criteria | p. 33 |
1.6 Summary | p. 36 |
References | p. 36 |
2 Malfunction Mechanism Analysis due to Nonlinearity of Transformer Core | |
2.1 Introduction | p. 39 |
2.2 The Ultra-Saturation Phenomenon of Loaded Transformer Energizing and its Impacts on Differential Protection | p. 43 |
2.2.1 Loaded Transformer Energizing Model Based Second Order Equivalent Circuit | p. 43 |
2.2.2 Preliminary Simulation Studies | p. 48 |
2.3 Studies on the Unusual Mal-Operation of Transformer Differential Protection during the Nonlinear Load Switch-In | p. 57 |
2.3.1 Simulation Model of the Nonlinear Load Switch-In | p. 57 |
2.3.2 Simulation Results and Analysis of Mal-Operation Mechanism of Differential Protection | p. 62 |
2.4 Analysis of a Sort of Unusual Mal-operation of Transformer Differential Protection the Removal of External Fault | p. 70 |
2.4.1 Modelling of the External Fault Inception and Removed and Current Transformer | p. 70 |
2.4.2 Analysis of Low Current Mal-operation of Differential Protection | p. 72 |
2.5 Analysis and Countermeasure of Abnormal Operation Behaviours of the Differential Protection of the Converter Transformer | p. 80 |
2.5.1 Recurrence and Analysis of the Reported Abnormal Operation of the Differential Protection of the Converter Transformer | p. 80 |
2.5.2 Time-difference criterion to Discriminate between Faults and Magnetizing Inrushes of the Converter Transformer | p. 86 |
2.6 Summary | p. 95 |
References | p. 95 |
3 Novel Analysis Tools on Operating Characteristics of Transformer Differential Protecion | p. 97 |
3.1 Introduction | p. 97 |
3.2 Studies on the Operation Behaviour of Differential Protection During a Loaded Transformer Energizing | p. 99 |
3.2.1 Simulation Models of Loaded Transformer Switch-On and CT | p. 99 |
3.2.2 Analysis of the Mal-operation Mechanism of Differential Protection | p. 102 |
3.3 Comparative Investigation on Current Differential Criteria between One Using Phase Current and One Using Phase-Phase Current Difference for the Transformer using Y-Delta Connection | p. 109 |
3.3.1 Analyses of Applying the Phase Current Differential to the Power Transformer with Y/¿ Connection and its Existing Bases | p. 109 |
3.3.2 Rationality Analyses of Applying the Phase Current Differential Criterion to the Power Transformer with Y/¿ Connection | p. 113 |
3.4 Comparative Analysis on Current Percentage Differential Protections Using a Novel Reliability Evaluation Criterion | p. 117 |
3.4.1 Introduction to CPD and NPD | p. 117 |
3.4.2 Performance Comparison between CPD and NPD in the Case of CT Saturation | p. 118 |
3.4.3 Performance Comparison between CPD and NPD in the Case of Internal Fault | p. 121 |
3.5 Comparative Studies on Percentage Differential Criteria Using Phase Current and Superimposed Phase Current | p. 123 |
3.5.1 The Dynamic Locus of $$$ in the Case of CT Saturation | p. 123 |
3.5.2 Sensitivety Comparison between the Phase Current Based and the Superimposed Current Based Differential Criteria | p. 126 |
3.5.3 Security Comparison between the Phase Current Based and the Superimposed Current Based Differential Criteria | p. 128 |
3.5.4 Simulation Analyses | p. 130 |
3.6 A Novel Analysis Methodology of Differential Protection Operation Behaviour | p. 132 |
3.6.1 The Relationship between Transforming Rate and the Angular Change Rate under CT Saturation | p. 132 |
3.6.2 Principles of Novel Percentage Restraint Criteria | p. 133 |
3.6.3 Analysis of Novel Percentage Differential Criteria | p. 142 |
3.7 Summary | p. 151 |
References | p. 151 |
4 Novel Magnetizing Inrush Identification Scheme | p. 153 |
4.1 Introduction | p. 153 |
4.2 Studies for Identification of the Inrush Based on Improved Correlation Algorithm | p. 155 |
4.2.1 Basic Principle of Waveform Correlation Scheme | p. 155 |
4.2.2 Design and Test of the Improved Waveform Correlation Principle | p. 159 |
4.3 A Novel Method for Discrimination of Internal Faults and Inrush Currents by Using Waveform Singularity Factor | p. 163 |
4.3.1 Waveform Singularity Factor Based Algorithm | p. 163 |
4.3.2 Testing Results and Analysis | p. 163 |
4.4 A New Principle of Discrimination between Inrush Current and Internal Fault Current of Transformer Based on Self-Correlation Function | p. 169 |
4.4.1 Basic Principle of Correlation Function Applied to Random Single Analysis | p. 169 |
4.4.2 Theory and Analysis of Waveform Similarity Based on Self-Correlation Function | p. 170 |
4.4.3 EPDL Testing Results and Analysis | p. 173 |
4.5 Identifying Inrush Current Using Sinusoidal Proximity Factor | p. 174 |
4.5.1 Sinusoidal Proximity Factor Based Algorithm|o174 | |
4.5.2 Testing Results and Analysis | p. 176 |
4.6 A Wavelet Transform Based Scheme for Power Transformer Inrush Identification | p. 181 |
4.6.1 Principle of Wavelet Transform | p. 181 |
4.6.2 Inrush Identification with WPT | p. 181 |
4.6.3 Result and Analysis | p. 185 |
4.7 A Novel Adaptive Scheme of Discrimination between Internal Faults and Inrush Currents of Transformer Using Mathematical Morphology | p. 190 |
4.7.1 Mathematical Morphology | p. 190 |
4.7.2 Principle and Scheme Design | p. 193 |
4.7.3 Testing Results and Analysis | p. 194 |
4.8 Identifying Tranformer Inrush Current Based on Normalized Grille Curve | p. 202 |
4.8.1 Normalized Grille Curve | p. 202 |
4.8.2 Experimental System | p. 205 |
4.8.3 Testing Results and Analysis | p. 207 |
4.9 A Novel Algorithm for Discrimination between Inrush Currents and Internal Faults Based on Equivalent Instantaneous Leakage Inductance | p. 211 |
4.9.1 Basic Principle | p. 211 |
4.9.2 EILI-Based Criterion | p. 217 |
4.9.3 Experimental Results and Analysis | p. 218 |
4.10 A Two-Terminal Network-Based Method for Discrimination between Internal Faults and Inrush Currents | p. 222 |
4.10.1 Basic Principle | p. 222 |
4.10.2 Experimental System | p. 230 |
4.10.3 Testing Results and Analysis | p. 230 |
4.11 Summary | p. 234 |
References | p. 234 |
5 Comprehensive Countermeasures for Improving the Performance of Transformer Differential Protection | p. 237 |
5.1 Introduction | p. 237 |
5.2 A Method to Eliminate the Magnetizing Inrush Current of Energized Transformers | p. 242 |
5.2.1 Principles and Modelling of the Inrush Suppressor and Parameter Design | p. 242 |
5.2.2 Simulation Validation and Results Analysis | p. 249 |
5.3 Identification of the Cross-Country Fault of a Power Transformer for Fast Unblocking of Differential Protection | p. 255 |
5.3.1 Criterion for Identifying Cross-Country Faults Using the Variation of the saturated Secondary Current with Respect to the Differential Current | p. 255 |
5.3.2 Simulation Analyses and Test Verification | p. 257 |
5.4 Adaptive Scheme in the Transformer Main Protection | p. 268 |
5.4.1 The Fundamental of the Time Difference Based Method to Discriminate between the Fault Current and the Inrush of the Transformer | p. 268 |
5.4.2 Preset Filter | p. 269 |
5.4.3 Comprehensive Protection Scheme | p. 271 |
5.4.4 Simulation Tests and Analysis | p. 274 |
5.5 A Series Multiresolution Morphological Gradient Based Criterion to Identify CT Saturation | p. 294 |
5.5.1 Time Difference Extraction Criterion Using Mathematical Morphology | p. 294 |
5.5.2 Simulation Study and Result Analysis | p. 297 |
5.5.3 Performance Verification with On-site Data | p. 297 |
5.6 A New Adaptive Method to Identify CT Saturation Using a Grille Fractal | p. 304 |
5.6.1 Analysis of the Behaviour of CT Transient Saturation | p. 304 |
5.6.2 The Basic Principle and Algorithm of Grille Fractal | p. 308 |
5.6.3 Self-Adaptive Generalized Morphological Filter | p. 312 |
5.6.4 The Design of Protection Program and the Verification of Results | p. 313 |
5.7 Summary | p. 317 |
References | p. 317 |
Index | p. 319 |