TY - BOOK AU - Del Vecchio,Robert M TI - Transformer design principles: with applications to core-form power transformers SN - 9781439805824 AV - TK2551 .T765 2010 PY - 2010///] CY - Boca Raton, FL PB - CRC Press/Taylor and Francis KW - Electric transformers KW - Design and construction N1 - Includes bibliographical references and index; Contents; Preface ; 1 Introduction ; 1.1 Historical Background ; 1.2 Uses in Power Systems ; 1.3 Core-Form and Shell-Form Transformers ; 1.4 Stacked and Wound Core Construction ; 1.5 Transformer Cooling ; 1.6 Winding Types ; 1.7 Insulation Structures ; 1.8 Structural Elements ; 1.9 Modern Trends ; 2 Magnetism and Related Core Issues ; 2.1 Introduction ; 2.2 Basic Magnetism ; 2.3 Hysteresis ; 2.4 Magnetic Circuits ; 2.5 Inrush Current ; 2.6 Distinguishing Inrush from Fault Current ; 2.7 Optimal Core Stacking ; 3 Circuit Model of a Two-Winding Transformer with Core ; 3.1 Introduction ; 3.2 Circuit Model of the Core ; 3.3 Two-Winding Transformer Circuit Model with Core ; 3.4 Approximate Two-Winding Transformer Circuit Model without Core ; 3.5 Vector Diagram of a Loaded Transformer with Core ; 3.6 Per-Unit System ; 3.7 Voltage Regulation ; 4 Reactance and Leakage Reactance Calculations ; 4.1 Introduction ; 4.2 General Method for Determining Inductances and Mutual Inductances ; 4.2.1 Energy by Magnetic Field Methods ; 4.2.2 Energy from Electric Circuit Methods ; 4.3 Two-Winding Leakage Reactance Formula ; 4.4 Ideal Two-, Three-, and Multiwinding Transformers ; 4.4.1 Ideal Autotransformers ; 4.5 Leakage Reactance for Two-Winding Transformers Based on Circuit Parameters ; 4.5.1 Leakage Reactance for a Two-Winding Autotransformer ; 4.6 Leakage Reactances for Three-Winding Transformers ; 4.6.1 Leakage Reactance for an Autotransformer with a Tertiary Winding ; 4.6.2 Leakage Reactance between Two Windings Connected in Series and a Third Winding ; 4.6.3 Leakage Reactance of a Two-Winding Autotransformer with X-Line Taps ; 4.6.4 More General Leakage Reactance Calculations ; 5 Phasors, Three-Phase Connections, and Symmetrical Components ; 5.1 Phasors ; 5.2 Wye and Delta Three-Phase Connections ; 5.3 Zig-Zag Connection ; 5.4 Scott Connection ; 5.5 Symmetrical Components ; 6 Fault Current Analysis ; 6.1 Introduction ; 6.2 Fault Current Analysis on Three-Phase Systems ; 6.2.1 Three-Phase Line-to-Ground Fault ; 6.2.2 Single-Phase Line-to-Ground Fault ; 6.2.3 Line-to-Line Fault ; 6.2.4 Double Line-to-Ground Fault ; 6.3 Fault Currents for Transformers with Two Terminals per Phase ; 6.3.1 Three-Phase Line-to-Ground Fault ; 6.3.2 Single-Phase Line-to-Ground Fault ; 6.3.3 Line-to-Line Fault ; 6.3.4 Double Line-to-Ground Fault ; 6.3.5 Zero-Sequence Circuits ; 6.3.6 Numerical Example for a Single Line-to-Ground Fault ; 6.4 Fault Currents for Transformers with Three Terminals per Phase ; 6.4.1 Three-Phase Line-to-Ground Fault ; 6.4.2 Single-Phase Line-to-Ground Fault ; 6.4.3 Line-to-Line Fault ; 6.4.4 Double Line-to-Ground Fault ; 6.4.5 Zero-Sequence Circuits ; 6.4.6 Numerical Examples ; 6.5 Asymmetry Factor ; 7 Phase-Shifting and Zig-Zag Transformers ; 7.1 Introduction ; 7.2 Basic Principles ; 7.3 Squashed Delta Phase-Shifting Transformer ; 7.3.1 Zero-Sequence Circuit Model ; 7.4 Standard Delta Phase-Shifting Transformer ; 7.4.1 Zero-Sequence Circuit Model ; 7.5 Two-Core Phase-Shifting Transformer ; 7.5.1 Zero-Sequence Circuit Model ; 7.6 Regulation Effects ; 7.7 Fault Current Analysis ; 7.7.1 Squashed Delta Fault Currents ; 7.7.2 Standard Delta Fault Currents ; 7.7.3 Two-Core Phase-Shifting Transformer Fault Currents ; 7.8 Zig-Zag Transformer ; 7.8.1 Calculation of Electrical Characteristics ; 7.8.2 Per-Unit Formulas ; 7.8.3 Zero-Sequence Impedance ; 7.8.4 Fault Current Analysis ; 8 Multiterminal Three-Phase Transformer Model ; 8.1 Introduction ; 8.2 Theory ; 8.2.1 Two-Winding Leakage Inductance ; 8.2.2 Multiwinding Transformers ; 8.2.3 Transformer Loading ; 8.3 Transformers with Winding Connections within a Phase ; 8.3.1 Two Secondary Windings in Series ; 8.3.2 Primary Winding in Series with a Secondary Winding ; 8.3.3 Autotransformer ; 8.4 Multiphase Transformers ; 8.4.1 Delta Connection ; 8.4.2 Zig-Zag Connection ; 8.5 Generalizing the Model ; 8.6 Regulation and Terminal Impedances ; 8.7 Multiterminal Transformer Model for Balanced and Unbalanced Load Conditions ; 8.7.1 Theory ; 8.7.2 Admittance Representation ; 8.7.2.1 Delta Winding Connection ; 8.7.3 Impedance Representation ; 8.7.3.1 Ungrounded Y Connection ; 8.7.3.2 Series-Connected Windings from the Same Phase ; 8.7.3.3 Zig-Zag Winding Connection ; 8.7.3.4 Autoconnection ; 8.7.3.5 Three Windings Joined ; 8.7.4 Terminal Loading ; 8.7.5 Solution Process ; 8.7.5.1 Terminal Currents and Voltages ; 8.7.5.2 Winding Currents and Voltages ; 8.7.6 Unbalanced Loading Examples ; 8.7.6.1 Autotransformer with Buried Delta Tertiary and Fault on Low-Voltage Terminal ; 8.7.6.2 Power Transformer with Fault on Delta Tertiary ; 8.7.6.3 Power Transformer with Fault on Ungrounded Y Secondary ; 8.7.7 Balanced Loading Example ; 8.7.7.1 Standard Delta Phase-Shifting Transformer ; 8.7.8 Discussion ; 9 Rabins' Method for Calculating Leakage Fields, Leakage Inductances, and Forces in Transformers ; 9.1 Introduction ; 9.2 Theory ; 9.3 Rabins' Formula for Leakage Reactance ; 9.3.1 Rabins' Method Applied to Calculate the Leakage Reactance between Two Windings That Occupy Different Radial Positions ; 9.3.2 Rabins' Method Applied to Calculate the Leakage Reactance between Two Axially Stacked Windings ; 9.3.3 Rabins' Method Applied to Calculate the Leakage Reactance for a Collection of Windings ; 9.4 Application of Rabins' Method to Calculate the Self-Inductance of and Mutual Inductance between Coil Sections ; 9.5 Determining the B-Field ; 9.6 Determination of Winding Forces ; 9.7 Numerical Considerations ; 10 Mechanical Design ; 10.1 Introduction ; 10.2 Force Calculations ; 10.3 Stress Analysis ; 10.3.1 Compressive Stress in the Key Spacers ; 10.3.2 Axial Bending Stress per Strand ; 10.3.3 Tilting Strength ; 10.3.4 Stress in the Tie Bars ; 10.3.5 Stress in the Pressure Ring ; 10.3.6 Hoop Stress ; 10.3.7 Radial Bending Stress ; 10.4 Radial Buckling Strength ; 10.4.1 Free Unsupported Buckling ; 10.4.2 Constrained Buckling ; 10.4.3 Experiment to Determine Buckling Strength ; 10.5 Stress Distribution in a Composite Wire-Paper Winding Section ; 10.6 Additional Mechanical Considerations ; 11 Electric Field Calculations ; 11.1 Simple Geometries ; 11.1.1 Planar Geometry ; 11.1.2 Cylindrical Geometry ; 11.1.3 Spherical Geometry ; 11.1.4 Cylinder-Plane Geometry ; 11.2 Electric Field Calculations Using Conformal Mapping ; 11.2.1 Physical Basis ; 11.2.2 Conformal Mapping ; 11.2.3 Schwarz-Christoffel Transformation ; 11.2.4 Conformal Map for the Electrostatic Field Problem ; 11.2.4.1 Electric Potential and Field Values ; 11.2.4.2 Calculations and Comparison with a Finite Element Solution ; 11.2.4.3 Estimating Enhancement Factors ; 11.3 Finite Element Electric Field Calculations ; 12 Capacitance Calculations ; 12.1 Introduction ; 12.2 Distributive Capacitance along a Winding or Disk ; 12.3 Stein's Disk Capacitance Formula ; 12.4 General Disk Capacitance Formula ; 12.5 Coil Grounded at One End with Grounded Cylinders on Either Side ; 12.6 Static Ring on One Side of a Disk ; 12.7 Terminal Disk without a Static Ring ; 12.8 Capacitance Matrix ; 12.9 Two Static Rings ; 12.10 Static Ring between the First Two Disks ; 12.11 Winding Disk Capacitances with Wound-in Shields ; 12.11.1 Analytic Formula ; 12.11.2 Circuit Model ; 12.11.3 Experimental Methods ; 12.11.4 Results ; 12.12 Multistart Winding Capacitance ; 13 Voltage Breakdown and High-Voltage Design ; 13.1 Introduction ; 13.2 Principles of Voltage Breakdown ; 13.2.1 Breakdown in Solid Insulation ; 13.2.2 Breakdown in Transformer Oil ; 13.3 Geometric Dependence of Transformer-Oil Breakdown ; 13.3.1 Theory ; 13.3.2 Planar Geometry ; 13.3.3 Cylindrical Geometry ; 13.3.4 Spherical Geometry ; 13.3.5 Comparison with Experiment ; 13.3.6 Generalization ; 13.3.6.1 Breakdown for the Cylinder-Plane Geometry ; 13.3.6.2 Breakdown for the Disk-Disk-to-Ground Plane Geometry ; 13.3.7 Discussion ; 13.4 Insulation Coordination ; 13.5 Continuum Model of Winding Used to Obtain the Impulse-Voltage; Distribution ; 13.5.1 Uniform Capacitance Model ; 13.5.2 Traveling Wave Theory ; 13.6 Lumped-Parameter Model for Transient Voltage Distribution ; 13.6.1 Circuit Description ; 13.6.2 Mutual and Self-Inductance Calculations ; 13.6.3 Capacitance Calculations ; 13.6.4 Impulse-Voltage Calculations and Experimental Comparisons ; 13.6.5 Sensitivity Studies ; 14 Losses ; 14.1 Introduction ; 14.2 No-Load or Core Losses ; 14.2.1 Building Factor ; 14.2.2 Interlaminar Losses ; 14.3 Load Losses ; 14.3.1 I2R Losses ; 14.3.2 Stray Losses ; 14.3.2.1 Eddy Current Losses in the Coils ; 14.3.2.2 Tieplate Losses ; 14.3.2.3 Tieplate and Core Losses Due to Unbalanced Currents ; 14.3.2.4 Tank and Clamp Losses ; 14.3.3 Stray Losses Obtained from 3D Finite Element Analyses ; 14.3.3.1 Shunts on the Clamps ; 14.3.3.2 Shunts on the Tank Wall ; 14.3.3.3 Effects of Three-Phase Currents on Losses ; 14.3.3.4 Stray Losses from the 3D Analysis versus Analytical and Test Losses ; 14.4 Tank and Shield Losses Due to Nearby Busbars ; 14.4.1 Losses Obtained with 2D Finite Element Study ; 14.4.2 Losses Obtained Analytically ; 14.4.2.1 Current Sheet ; 14.4.2.2 Delta Function Current ; 14.4.2.3 Collection of Delta Function Currents ; 14.4.2.4 Model Studies ; 14.5 Tank Losses Associated with the Bushings ; 14.5.1 Comparison with a 3D Finite Element Calculation ; 15 Thermal Design ; 15.1 Introduction ; 15.2 Thermal Model of a Disk Coil with Directed Oil Flow ; 15.2.1 Oil Pressures and Velocities ; 15.2.2 Oil Nodal Temperatures and Path Temperature Rises ; 15.2.3 Disk Temperatures ; 15.3 Thermal Model for Coils without Directed Oil Flow ; 15.4 Radiator Thermal Model ; 15.5 Tank Cooling ; 15.6 Oil Mixing in the Tank ; 15.7 Time Dependence ; 15.8 Pumped Flow ; 15.9 Comparison with Test Results ; 15.10 Determining m and n Exponents ; 15.11 Loss of Life Calculation ; 15.12 Cable and Lead Temperature Calculation ; 15.13 Tank Wall Temperature Calculation ; 15.14 Tieplate Temperature ; 15.15 Core Steel Temperature Calculation ; 16 Load Tap Changers ; 16.1 Introduction ; 16.2 General Description of Load Tap Changers ; 16.3 Types of Regulation ; 16.4 Principles of Operation ; 16.4.1 Resistive Switching ; 16.4.2 Reactive Switching with Preventive Autotransformers ; 16.5 Connection Schemes ; 16.5.1 Power Transformers ; 16.5.2 Autotransformers ; 16.5.3 Use of Auxiliary Transformers ; 16.5.4 Phase-Shifting Transformers ; 16.5.5 Reduced versus Full-Rated Taps ; 16.6 General Maintenance ; 17 Miscellaneous Topics ; 17.1 Setting the Impulse Test Generator to Achieve Close to Ideal Waveshapes ; 17.1.1 Impulse Generator Circuit Model ; 17.1.2 Transformer Circuit Model ; 17.1.3 Determining the Generator Settings for Approximating the Ideal Waveform ; 17.1.4 Practical Implementation ; 17.2 Impulse or Lightning Strike on a Transformer through a Length of Cable ; 17.2.1 Lumped Parameter Model ; 17.2.1.1 Numerical Example ; 17.2.2 Traveling Wave Theory ; 17.3 Air Core Inductance ; 17.4 Electrical Contacts ; 17.4.1 Contact Resistance ; 17.4.2 Thermal Considerations ; 17.4.3 Practical Considerations ; References ; Index ER -