Detail of GB/T 1094.4-2005

Introduction of GB/T 1094.4-2005

1 Scope This Part gives guidance and explanatory comments on the existing procedures for lightning and switching impulse testing of power transformers to supplement the requirements of GB 1094.3. It is also generally applicable to the testing of reactors (see GB/T 10229), modifications to power transformer procedures being indicated where required. This Part gives the information on waveshapes, test circuits including test connections, earthing practices, failure detection methods, test procedures, measuring techniques and interpretation of results. Where applicable, the test techniques specified in this Part are as recommended in GB/T 16927.1 and GB/T 16927.2. 2 Normative References The following normative documents contain provisions which, through reference in this text, constitute provisions of this Part of GB 1094. For dated references, subsequent amendments to, or revisions of, any of these publications do not apply. However, parties to agreements based on this Standard are encouraged to investigate the possibility of applying the most recent editions of the normative documents indicated below. For undated references, the latest edition of the normative documents referred to applies. GB 1094.3 Power Transformers — Part 3: Insulation Levels, Dielectric Tests and External Clearances in Air (GB 1094.3-2003, IEC 60076-3:2000, MOD) GB/T 10229 Reactors (GB/T 10229-1988, eqv IEC 60289:1987) GB/T 16896.1 Digital Recorders for Measurements in High-voltage Impulse Tests – Part 1: Requirements for Digital Recorders (GB/T 16896.1-1997, eqv IEC 61083-1:1991) GB/T 16927.1 High Voltage Test Techniques — Part 1: General Test Requirements (GB/T 16896.1-1997, eqv IEC 61083-1:1991) GB/T 16927.2 High Voltage Test Techniques — Part 2: Measuring Systems (GB/T 16927.1-1997, eqv IEC 60060-1:1989) IEC 61083-2 Digital Recorders for Measurements in High-voltage Impulse Tests — Part 2: Evaluation of Software Used for the Determination of the Parameters of Impulse Waveforms

Contents of GB/T 1094.4-2005

Foreword IV 1 Scope 2 Normative References 3 General 4 Specified Waveshapes 5 Test Circuit 6 Calibration 7 Lightning Impulse Tests 7.1 Waveshapes 7.2 Impulses chopped on the tail 7.3 Terminal connections and applicable methods of failure detection 7.4 Test procedures 7.5 Recording of tests 8 Switching Impulse Tests 8.1 Special requirements 8.2 Transformers 8.3 Reactors 9 Interpretation of Oscillograms or Digital Recordings 9.1 Lightning impulse 9.2 Switching impulse 10 Digital Processing, Including Transfer Function Analysis 11 Impulse Test Reports Appendix A (Informative) Principles of Waveshape Control A.1 General A.2 High-impedance windings (Lt > 100 mH) A.3 Low-impedance windings (Lt < 20 mH) Appendix B (Informative) Typical Oscillograms and Digital Recordings Figure 1 Typical Impulse Test Circuit Figure 2 Lightning Impulse Test Terminal Connections and Applicable Methods of Failure Detection Figure 3 Transformer and Reactor Switching Impulse Waveshapes Figure 4 Switching Impulse Test Terminal Connections and Methods of Failure Detection Figure A.1 Waveshape Control for High-impedance Windings Figure A.2 Wavetail Control for Low Impedance Windings Figure A.3 Damped Oscillation Figure A.4 Effects Due to Short Length of Wavetail Figure A.5 Winding Earthed Through a Resistor Figure A.6 Resistance Earthing of Low-impedance Windings Figure B.1 Lightning Impulse, Full-wave Failure — Line-to-neutral Breakdown Across High-voltage Winding of 400 kV Generator Transformer Figure B.2 Lightning Impulse, Full-wave Failure — Breakdown between Discs at Entrance to High-voltage Winding of 115 kV Transformer Figure B.3 Lightning Impulse, Interlayer Breakdown in Coarse-step Tapping Winding of a 400 kV/220 kV Transformer Figure B.4 Lightning Impulse, Full-wave Failure — Breakdown between Leads of Two 1.1 % Sections of Outside Tapping Winding of 400 kV Generator Transformer Figure B.5 Lightning Impulse, Full-wave Failure — Breakdown Short-circuiting one Section of the Fine-step Tapping Winding of a 220 kV Transformer Figure B.6 Lightning Impulse, Full-wave Failure — Breakdown between Parallel Conductors of a Main High-voltage Winding of a 220/110 kV Transformer Figure B.7 Lightning Impulse, Full-wave Failure — Breakdown between Foils of 66 kV Bushing on Tested Winding Figure B.8 Lightning Impulse, Chopped-wave Failure — Breakdown between Turns in the main High-voltage Winding of a 115 kV Transformer Figure B.9 Lightning Impulse, Chopped-wave Failure — Breakdown between Turns in a Fine-step Tapping Winding of a 220 kV Transformer Figure B.10 Chopped Lightning Impulse — Impulses at Different Voltage Levels with Identical Times to Chopping when Testing a 115 kV Transformer Figure B.11 Chopped Lightning Impulse — Effects of Differences in Times to Chopping When Testing a 220 kV Transformer Figure B.12 Full Lightning Impulse — Effect of Non-linear Resistors Embodied in Neutral End On-load Tap-changer of a Transformer with Separate Windings Figure B.13 Full Lightning Impulse — Effect of Generator Firing Differences at Different Voltage Levels When Testing a 400 kV Transformer Figure B.14 Switching Impulse — Satisfactory Test on a 400 kV Three-phase Generator Transformer Figure B.15 Switching Impulse — Breakdown by Axial Flashover of the Main High-voltage Winding of a 525 kV Single-phase, Generator Transformer Figure B.16 Switching Impulse — Satisfactory Test on a 33 Mvar, 525 kV Single-phase Shunt Reactor Figure B.17 Lightning Impulse — Comparison of the Transfer Function of a Full Wave and a Chopped Wave Figure B.18 Full Lightning Impulse — Evaluation of a Non-standard Waveshape — Influence of In-built Smoothing Algorithms in Digitizers Figure B.19 Full Lightning Impulse — Non-standard Waveshape, Superimposed Oscillations with > 50 % Amplitude and Frequency < 0.5 MHz Figure B.20 Chopped Lightning Impulse — Non-standard Chopped Wave on a Layer Type Winding Figure B.21 Full lightning Impulse — Non-standard Waveshape, Comparison of Non-standard Waveshapes by Digitizers of Different Make from the Same Recording Figure B.22 Full Lightning Impulse — Test-circuit Problem Caused by a Sparkover to Earth from a Measuring Cable Figure B.23 Full Lightning Impulse — Failure Digital Recordings of a Flashover between Tap Leads of a Tap Changer and of a Flashover between Coarse and Fine Tapping Windings