This part of IEC 60071 constitutes application guidelines and deals with the selection of insulation levels of equipment or installations for three-phase a.c. systems. Its aim is to give guidance for the determination of the rated withstand voltages for ranges I and II of IEC 60071- 1 and to justify the association of these rated values with the standardized highest voltages for equipment. This association is for insulation co-ordination purposes only. The requirements for human safety are not covered by this document. This document covers three-phase a.c. systems with nominal voltages above 1 kV. The values derived or proposed herein are generally applicable only to such systems. However, the concepts presented are also valid for two-phase or single-phase systems. This document covers phase-to-earth, phase-to-phase and longitudinal insulation. This document is not intended to deal with routine tests. These are to be specified by the relevant product committees. The content of this document strictly follows the flow chart of the insulation co-ordination process presented in Figure 1 of IEC 60071-1:2019. Clauses 5 to 8 correspond to the squares in this flow chart and give detailed information on the concepts governing the insulation coordination process which leads to the establishment of the required withstand levels. This document emphasizes the necessity of considering, at the very beginning, all origins, all classes and all types of voltage stresses in service irrespective of the range of highest voltage for equipment. Only at the end of the process, when the selection of the standard withstand voltages takes place, does the principle of covering a particular service voltage stress by a standard withstand voltage apply. Also, at this final step, this document refers to the correlation made in IEC 60071-1 between the standard insulation levels and the highest voltage for equipment. The annexes contain examples and detailed information which explain or support the concepts described in the main text, and the basic analytical techniques used.<\/p>\n
| PDF Pages<\/th>\n | PDF Title<\/th>\n<\/tr>\n | ||||||
|---|---|---|---|---|---|---|---|
| 1<\/td>\n | 30481456 <\/td>\n<\/tr>\n | ||||||
| 246<\/td>\n | A-30387030 <\/td>\n<\/tr>\n | ||||||
| 247<\/td>\n | undefined <\/td>\n<\/tr>\n | ||||||
| 250<\/td>\n | Annex ZA (normative)Normative references to international publicationswith their corresponding European publications <\/td>\n<\/tr>\n | ||||||
| 251<\/td>\n | English CONTENTS <\/td>\n<\/tr>\n | ||||||
| 258<\/td>\n | FOREWORD <\/td>\n<\/tr>\n | ||||||
| 260<\/td>\n | 1 Scope 2 Normative references <\/td>\n<\/tr>\n | ||||||
| 261<\/td>\n | 3 Terms, definitions, abbreviated terms and symbols 3.1 Terms and definitions 3.2 Abbreviated terms <\/td>\n<\/tr>\n | ||||||
| 262<\/td>\n | 3.3 Symbols <\/td>\n<\/tr>\n | ||||||
| 267<\/td>\n | 4 Concepts governing the insulation co-ordination <\/td>\n<\/tr>\n | ||||||
| 268<\/td>\n | 5 Representative voltage stresses in service 5.1 Origin and classification of voltage stresses 5.2 Characteristics of overvoltage protection devices 5.2.1 General remarks <\/td>\n<\/tr>\n | ||||||
| 269<\/td>\n | 5.2.2 Metal-oxide surge arresters without gaps (MOSA) <\/td>\n<\/tr>\n | ||||||
| 271<\/td>\n | 5.2.3 Line surge arresters (LSA) for overhead transmission and distribution lines 5.3 General approach for the determination of representative voltages and overvoltages 5.3.1 Continuous (power-frequency) voltage 5.3.2 Temporary overvoltages <\/td>\n<\/tr>\n | ||||||
| 275<\/td>\n | 5.3.3 Slow-front overvoltages <\/td>\n<\/tr>\n | ||||||
| 277<\/td>\n | Figures Figure 1 \u2013 Range of 2 % slow-front overvoltages at the receiving end due to line energization and re-energization [27] <\/td>\n<\/tr>\n | ||||||
| 278<\/td>\n | Figure 2 \u2013 Ratio between the 2 % values of slow-front overvoltages phase-to-phase and phase-to-earth [28], [29] <\/td>\n<\/tr>\n | ||||||
| 281<\/td>\n | 5.3.4 Fast-front overvoltages <\/td>\n<\/tr>\n | ||||||
| 285<\/td>\n | 5.3.5 Very-fast-front overvoltages Figure 3 \u2013 Diagram for surge arrester connection to the protected object <\/td>\n<\/tr>\n | ||||||
| 286<\/td>\n | 5.4 Determination of representative overvoltages by detailed simulations 5.4.1 General overview 5.4.2 Temporary overvoltages <\/td>\n<\/tr>\n | ||||||
| 287<\/td>\n | 5.4.3 Slow-front overvoltages <\/td>\n<\/tr>\n | ||||||
| 288<\/td>\n | 5.4.4 Fast-front overvoltages <\/td>\n<\/tr>\n | ||||||
| 291<\/td>\n | Figure 4 \u2013 Modelling of transmission lines and substations\/power stations <\/td>\n<\/tr>\n | ||||||
| 292<\/td>\n | 5.4.5 Very-fast-front overvoltages <\/td>\n<\/tr>\n | ||||||
| 293<\/td>\n | 6 Co-ordination withstand voltage 6.1 Insulation strength characteristics 6.1.1 General <\/td>\n<\/tr>\n | ||||||
| 294<\/td>\n | 6.1.2 Influence of polarity and overvoltage shapes <\/td>\n<\/tr>\n | ||||||
| 295<\/td>\n | 6.1.3 Phase-to-phase and longitudinal insulation <\/td>\n<\/tr>\n | ||||||
| 296<\/td>\n | 6.1.4 Influence of weather conditions on external insulation 6.1.5 Probability of disruptive discharge of insulation <\/td>\n<\/tr>\n | ||||||
| 298<\/td>\n | 6.2 Performance criterion 6.3 Insulation co-ordination procedures 6.3.1 General <\/td>\n<\/tr>\n | ||||||
| 299<\/td>\n | 6.3.2 Insulation co-ordination procedures for continuous (power-frequency) voltage and temporary overvoltage <\/td>\n<\/tr>\n | ||||||
| 300<\/td>\n | 6.3.3 Insulation co-ordination procedures for slow-front overvoltages Figure 5 \u2013 Distributive discharge probability of self-restoring insulation described on a linear scale <\/td>\n<\/tr>\n | ||||||
| 301<\/td>\n | Figure 6 \u2013 Disruptive discharge probability of self-restoring insulation described on a Gaussian scale Figure 7 \u2013 Evaluation of deterministic co-ordination factor Kcd <\/td>\n<\/tr>\n | ||||||
| 302<\/td>\n | Figure 8 \u2013 Evaluation of the risk of failure <\/td>\n<\/tr>\n | ||||||
| 304<\/td>\n | 6.3.4 Insulation co-ordination procedures for fast-front overvoltages Figure 9 \u2013 Risk of failure of external insulation for slow-front overvoltages as a function of the statistical co-ordination factor Kcs <\/td>\n<\/tr>\n | ||||||
| 305<\/td>\n | 6.3.5 Insulation co-ordination procedures for very-fast-front overvoltages 7 Required withstand voltage 7.1 General remarks 7.2 Atmospheric correction 7.2.1 General remarks <\/td>\n<\/tr>\n | ||||||
| 306<\/td>\n | 7.2.2 Altitude correction <\/td>\n<\/tr>\n | ||||||
| 307<\/td>\n | 7.3 Safety factors 7.3.1 General Figure 10 \u2013 Dependence of exponent m on the co-ordination switching impulse withstand voltage <\/td>\n<\/tr>\n | ||||||
| 308<\/td>\n | 7.3.2 Ageing 7.3.3 Production and assembly dispersion 7.3.4 Inaccuracy of the withstand voltage 7.3.5 Recommended safety factors (Ks) <\/td>\n<\/tr>\n | ||||||
| 309<\/td>\n | 8 Standard withstand voltage and testing procedures 8.1 General remarks 8.1.1 Overview 8.1.2 Standard switching impulse withstand voltage 8.1.3 Standard lightning impulse withstand voltage <\/td>\n<\/tr>\n | ||||||
| 310<\/td>\n | 8.2 Test conversion factors 8.2.1 Range I 8.2.2 Range II Tables Table 1 \u2013 Test conversion factors for range I, to convert required SIWV to SDWV and LIWV <\/td>\n<\/tr>\n | ||||||
| 311<\/td>\n | 8.3 Determination of insulation withstand by type tests 8.3.1 Test procedure dependency upon insulation type 8.3.2 Non-self-restoring insulation 8.3.3 Self-restoring insulation Table 2 \u2013 Test conversion factors for range II to convert required SDWV to SIWV <\/td>\n<\/tr>\n | ||||||
| 312<\/td>\n | 8.3.4 Mixed insulation Table 3 \u2013 Selectivity of test procedures B and C of IEC 60060-1 <\/td>\n<\/tr>\n | ||||||
| 313<\/td>\n | 8.3.5 Limitations of the test procedures 8.3.6 Selection of the type test procedures 8.3.7 Selection of the type test voltages Figure 11 \u2013 Probability P of an equipment to pass the test dependent on the difference K between the actual and the rated impulse withstand voltage <\/td>\n<\/tr>\n | ||||||
| 314<\/td>\n | 9 Special considerations for apparatus and transmission line 9.1 Overhead line 9.1.1 General <\/td>\n<\/tr>\n | ||||||
| 315<\/td>\n | 9.1.2 Insulation co-ordination for operating voltages and temporary overvoltages 9.1.3 Insulation co-ordination for slow-front overvoltages <\/td>\n<\/tr>\n | ||||||
| 316<\/td>\n | 9.1.4 Insulation co-ordination for fast-front overvoltages <\/td>\n<\/tr>\n | ||||||
| 317<\/td>\n | 9.2 Cable line 9.2.1 General 9.2.2 Insulation co-ordination for operating voltages and temporary overvoltages 9.2.3 Insulation co-ordination for slow-front overvoltages <\/td>\n<\/tr>\n | ||||||
| 318<\/td>\n | 9.2.4 Insulation co-ordination for fast-front overvoltages 9.2.5 Overvoltage protection of cable lines <\/td>\n<\/tr>\n | ||||||
| 319<\/td>\n | 9.3 GIL (gas insulated transmission line) \/ GIB (Gas-insulated busduct) 9.3.1 General 9.3.2 Insulation co-ordination for operating voltages and temporary overvoltages 9.3.3 Insulation co-ordination for slow-front overvoltages <\/td>\n<\/tr>\n | ||||||
| 320<\/td>\n | 9.3.4 Insulation co-ordination for fast-front overvoltages 9.3.5 Overvoltage protection of GIL\/GIB lines 9.4 Substation 9.4.1 General Figure 12 \u2013 Example of a schematic substation layout used for the overvoltage stress location <\/td>\n<\/tr>\n | ||||||
| 321<\/td>\n | 9.4.2 Insulation co-ordination for overvoltages <\/td>\n<\/tr>\n | ||||||
| 324<\/td>\n | Annexes Annex A (informative) Determination of temporary overvoltages due to earth faults <\/td>\n<\/tr>\n | ||||||
| 325<\/td>\n | Figure A.1 \u2013 Earth fault factor k on a base of X0\/X1 for R1\/X1 = Rf = 0 Figure A.2 \u2013 Relationship between R0\/X1 and X0\/X1 for constant values of earth fault factor k where R1 = 0 <\/td>\n<\/tr>\n | ||||||
| 326<\/td>\n | Figure A.3 \u2013 Relationship between R0\/X1 and X0\/X1 for constant values of earth fault factor k where R1 = 0,5 X1 Figure A.4 \u2013 Relationship between R0\/X1 and X0\/X1 for constant values of earth fault factor k where R1 = X1 <\/td>\n<\/tr>\n | ||||||
| 327<\/td>\n | Figure A.5 \u2013 Relationship between R0\/X1 and X0\/X1 for constant values of earth fault factor k where R1 = 2X1 <\/td>\n<\/tr>\n | ||||||
| 328<\/td>\n | Annex B (informative) Weibull probability distributions B.1 General remarks <\/td>\n<\/tr>\n | ||||||
| 329<\/td>\n | B.2 Disruptive discharge probability of external insulation <\/td>\n<\/tr>\n | ||||||
| 331<\/td>\n | Table B.1 \u2013 Breakdown voltage versus cumulative flashover probability \u2013 Single insulation and 100 parallel insulations <\/td>\n<\/tr>\n | ||||||
| 332<\/td>\n | B.3 Cumulative frequency distribution of overvoltages <\/td>\n<\/tr>\n | ||||||
| 334<\/td>\n | Figure B.1 \u2013 Conversion chart for the reduction of the withstand voltage due to placing insulation configurations in parallel <\/td>\n<\/tr>\n | ||||||
| 335<\/td>\n | Annex C (informative) Determination of the representative slow-front overvoltage due to line energization and re-energization C.1 General remarks C.2 Probability distribution of the representative amplitude of the prospective overvoltage phase-to-earth Figure C.1 \u2013 Probability density and cumulative distribution for derivation of the representative overvoltage phase-to-earth <\/td>\n<\/tr>\n | ||||||
| 338<\/td>\n | C.3 Probability distribution of the representative amplitude of the prospective overvoltage phase-to-phase <\/td>\n<\/tr>\n | ||||||
| 339<\/td>\n | C.4 Insulation characteristic <\/td>\n<\/tr>\n | ||||||
| 342<\/td>\n | C.5 Numerical example <\/td>\n<\/tr>\n | ||||||
| 343<\/td>\n | Figure C.2 \u2013 Example for bivariate phase-to-phase overvoltage curves with constant probability density and tangents giving the relevant 2 % values <\/td>\n<\/tr>\n | ||||||
| 344<\/td>\n | Figure C.3 \u2013 Principle of the determination of the representative phase-to-phase overvoltage Upre <\/td>\n<\/tr>\n | ||||||
| 345<\/td>\n | Figure C.4 \u2013 Schematic phase-phase-earth insulation configuration Figure C.5 \u2013 Description of the 50 % switching impulse flashover voltage ofa phase-phase-earth insulation <\/td>\n<\/tr>\n | ||||||
| 346<\/td>\n | Figure C.6 \u2013 Inclination angle of the phase-to-phase insulation characteristic in range “b” dependent on the ratio of the phase-phase clearance Dto the height Ht above earth <\/td>\n<\/tr>\n | ||||||
| 347<\/td>\n | Annex D (informative) Transferred overvoltages in transformers D.1 General remarks <\/td>\n<\/tr>\n | ||||||
| 348<\/td>\n | D.2 Transferred temporary overvoltages D.3 Capacitively transferred surges <\/td>\n<\/tr>\n | ||||||
| 350<\/td>\n | D.4 Inductively transferred surges <\/td>\n<\/tr>\n | ||||||
| 352<\/td>\n | Figure D.1 \u2013 Distributed capacitances of the windings of a transformer and the equivalent circuit describing the windings <\/td>\n<\/tr>\n | ||||||
| 353<\/td>\n | Figure D.2 \u2013 Values of factor J describing the effect of the winding connections on the inductive surge transference <\/td>\n<\/tr>\n | ||||||
| 354<\/td>\n | Annex E (informative) Determination of lightning overvoltages by simplified method E.1 General remarks E.2 Determination of the limit distance (Xp) E.2.1 Protection with arresters in the substation <\/td>\n<\/tr>\n | ||||||
| 355<\/td>\n | E.2.2 Self-protection of substation Table E.1 \u2013 Corona damping constant Kco <\/td>\n<\/tr>\n | ||||||
| 356<\/td>\n | E.3 Estimation of the representative lightning overvoltage amplitude E.3.1 General E.3.2 Shielding penetration <\/td>\n<\/tr>\n | ||||||
| 357<\/td>\n | E.3.3 Back flashovers <\/td>\n<\/tr>\n | ||||||
| 359<\/td>\n | E.4 Simplified approach <\/td>\n<\/tr>\n | ||||||
| 361<\/td>\n | E.5 Assumed maximum value of the representative lightning overvoltage Table E.2 \u2013 Factor A for various overhead lines <\/td>\n<\/tr>\n | ||||||
| 363<\/td>\n | Annex F (informative) Calculation of air gap breakdown strength from experimental data F.1 General F.2 Insulation response to power-frequency voltages <\/td>\n<\/tr>\n | ||||||
| 364<\/td>\n | F.3 Insulation response to slow-front overvoltages <\/td>\n<\/tr>\n | ||||||
| 365<\/td>\n | F.4 Insulation response to fast-front overvoltages <\/td>\n<\/tr>\n | ||||||
| 367<\/td>\n | Table F.1 \u2013 Typical gap factors K for switching impulse breakdown phase-to-earth (according to [1] and [4]) <\/td>\n<\/tr>\n | ||||||
| 368<\/td>\n | Table F.2 \u2013 Gap factors for typical phase-to-phase geometries <\/td>\n<\/tr>\n | ||||||
| 369<\/td>\n | Annex G (informative) Examples of insulation co-ordination procedure G.1 Overview G.2 Numerical example for a system in range I (with nominal voltage of 230 kV) G.2.1 General <\/td>\n<\/tr>\n | ||||||
| 370<\/td>\n | G.2.2 Part 1: no special operating conditions <\/td>\n<\/tr>\n | ||||||
| 376<\/td>\n | Table G.1 \u2013 Summary of minimum required withstand voltages obtained for the example shown in G.2.2 <\/td>\n<\/tr>\n | ||||||
| 377<\/td>\n | G.2.3 Part 2: influence of capacitor switching at station 2 <\/td>\n<\/tr>\n | ||||||
| 378<\/td>\n | Table G.2 \u2013 Summary of required withstand voltages obtained for the example shown in G.2.3 <\/td>\n<\/tr>\n | ||||||
| 379<\/td>\n | G.2.4 Part 3: flow charts related to the example of Clause G.2 <\/td>\n<\/tr>\n | ||||||
| 384<\/td>\n | G.3 Numerical example for a system in range II (with nominal voltage of 735 kV) G.3.1 General G.3.2 Step 1: determination of the representative overvoltages \u2013 values of Urp <\/td>\n<\/tr>\n | ||||||
| 385<\/td>\n | G.3.3 Step 2: determination of the co-ordination withstand voltages \u2013 values of Ucw <\/td>\n<\/tr>\n | ||||||
| 386<\/td>\n | G.3.4 Step 3: determination of the required withstand voltages \u2013 values of Urw <\/td>\n<\/tr>\n | ||||||
| 387<\/td>\n | G.3.5 Step 4: conversion to switching impulse withstand voltages (SIWV) <\/td>\n<\/tr>\n | ||||||
| 388<\/td>\n | G.3.6 Step 5: selection of standard insulation levels G.3.7 Considerations relative to phase-to-phase insulation co-ordination <\/td>\n<\/tr>\n | ||||||
| 389<\/td>\n | G.3.8 Phase-to-earth clearances <\/td>\n<\/tr>\n | ||||||
| 390<\/td>\n | G.3.9 Phase-to-phase clearances G.4 Numerical example for substations in distribution systems with Um up to 36 kV in range I G.4.1 General <\/td>\n<\/tr>\n | ||||||
| 391<\/td>\n | G.4.2 Step 1: determination of the representative overvoltages \u2013 values of Urp G.4.3 Step 2: determination of the co-ordination withstand voltages \u2013 values of Ucw <\/td>\n<\/tr>\n | ||||||
| 392<\/td>\n | G.4.4 Step 3: determination of required withstand voltages \u2013 values of Urw <\/td>\n<\/tr>\n | ||||||
| 393<\/td>\n | G.4.5 Step 4: conversion to standard short-duration power-frequency and lightning impulse withstand voltages <\/td>\n<\/tr>\n | ||||||
| 394<\/td>\n | G.4.6 Step 5: selection of standard withstand voltages G.4.7 Summary of insulation co-ordination procedure for the example of Clause G.4 <\/td>\n<\/tr>\n | ||||||
| 395<\/td>\n | Table G.3 \u2013 Values related to the insulation co-ordination procedure for the example in G.4 <\/td>\n<\/tr>\n | ||||||
| 396<\/td>\n | Annex H (informative) Atmospheric correction \u2013 Altitude correction application example H.1 General principles H.1.1 Atmospheric correction in standard tests <\/td>\n<\/tr>\n | ||||||
| 397<\/td>\n | H.1.2 Task of atmospheric correction in insulation co-ordination Figure H.1 \u2013 Principle of the atmospheric correction during test of a specified insulation level according to the procedure of IEC 60060-1 <\/td>\n<\/tr>\n | ||||||
| 398<\/td>\n | Figure H.2 \u2013 Principal task of the atmospheric correction in insulation co-ordination according to IEC 60071-1 <\/td>\n<\/tr>\n | ||||||
| 399<\/td>\n | H.2 Atmospheric correction in insulation co-ordination H.2.1 Factors for atmospheric correction H.2.2 General characteristics for moderate climates <\/td>\n<\/tr>\n | ||||||
| 400<\/td>\n | H.2.3 Special atmospheric conditions <\/td>\n<\/tr>\n | ||||||
| 401<\/td>\n | H.2.4 Altitude dependency of air pressure Figure H.3 \u2013 Comparison of atmospheric correction \u03b4 \u00d7 kh with relative air pressure p\/p0 for various weather stations around the world <\/td>\n<\/tr>\n | ||||||
| 402<\/td>\n | H.3 Altitude correction H.3.1 Definition of the altitude correction factor Figure H.4 \u2013 Deviation of simplified pressure calculation by exponential function in this document from the temperature dependent pressure calculation of ISO 2533 <\/td>\n<\/tr>\n | ||||||
| 403<\/td>\n | H.3.2 Principle of altitude correction <\/td>\n<\/tr>\n | ||||||
| 404<\/td>\n | H.3.3 Altitude correction for standard equipment operating at altitudes up to 1 000 m Figure H.5 \u2013 Principle of altitude correction: decreasing withstand voltage U10 of equipment with increasing altitude <\/td>\n<\/tr>\n | ||||||
| 405<\/td>\n | H.3.4 Altitude correction for standard equipment operating at altitudes above 1 000 m H.4 Selection of the exponent m H.4.1 General <\/td>\n<\/tr>\n | ||||||
| 406<\/td>\n | H.4.2 Derivation of exponent m for switching impulse voltage <\/td>\n<\/tr>\n | ||||||
| 408<\/td>\n | H.4.3 Derivation of exponent m for critical switching impulse voltage Figure H.6 \u2013 Sets of m-curves for standard switching impulse voltage including the variations in altitude for each gap factor Figure H.7 \u2013 Exponent m for standard switching impulse voltage for selected gap factors covering altitudes up to 4 000 m <\/td>\n<\/tr>\n | ||||||
| 409<\/td>\n | Figure H.8 \u2013 Sets of m-curves for critical switching impulse voltage including the variations in altitude for each gap factor Figure H.9 \u2013 Exponent m for critical switching impulse voltage for selected gap factors covering altitudes up to 4 000 m <\/td>\n<\/tr>\n | ||||||
| 410<\/td>\n | Figure H.10 \u2013 Accordance of m-curves from Figure 10 with determination of exponent m by means of critical switching impulse voltage for selected gap factors and altitudes Table H.1 \u2013 Comparison of functional expressions of Figure 10 with the selected parameters from the derivation of m-curves with critical switching impulse <\/td>\n<\/tr>\n | ||||||
| 411<\/td>\n | Annex I (informative) Evaluation method of non-standard lightning overvoltage shape for representative voltages and overvoltages I.1 General remarks I.2 Lightning overvoltage shape I.3 Evaluation method for GIS I.3.1 Experiments <\/td>\n<\/tr>\n | ||||||
| 412<\/td>\n | I.3.2 Evaluation of overvoltage shape I.4 Evaluation method for transformer I.4.1 Experiments <\/td>\n<\/tr>\n | ||||||
| 413<\/td>\n | I.4.2 Evaluation of overvoltage shape Figure I.1 \u2013 Examples of lightning overvoltage shapes <\/td>\n<\/tr>\n | ||||||
| 414<\/td>\n | Figure I.2 \u2013 Example of insulation characteristics with respect to lightning overvoltages of the SF6 gas gap (Shape E) Figure I.3 \u2013 Calculation of duration time Td Table I.1 \u2013 Evaluation of the lightning overvoltage in the GIS of UHV system <\/td>\n<\/tr>\n | ||||||
| 415<\/td>\n | Figure I.4 \u2013 Shape evaluation flow for GIS and transformer <\/td>\n<\/tr>\n | ||||||
| 416<\/td>\n | Figure I.5 \u2013 Application to GIS lightning overvoltage Figure I.6 \u2013 Example of insulation characteristics with respect to lightning overvoltage of the turn-to-turn insulation (Shape C) <\/td>\n<\/tr>\n | ||||||
| 417<\/td>\n | Figure I.7 \u2013 Application to transformer lightning overvoltage Table I.2 \u2013 Evaluation of lightning overvoltage in the transformer of 500 kV system <\/td>\n<\/tr>\n | ||||||
| 418<\/td>\n | Annex J (informative) Insulation co-ordination for very-fast-front overvoltages in UHV substations J.1 General J.2 Influence of disconnector design <\/td>\n<\/tr>\n | ||||||
| 419<\/td>\n | J.3 Insulation co-ordination for VFFO <\/td>\n<\/tr>\n | ||||||
| 420<\/td>\n | Figure J.1 \u2013 Insulation co-ordination for very-fast-front overvoltages <\/td>\n<\/tr>\n | ||||||
| 421<\/td>\n | Annex K (informative) Application of shunt reactors to limit TOV and SFO of high voltage overhead transmission line K.1 General remarks K.2 Limitation of TOV and SFO K.3 Application of the neutral grounding reactor to limit resonance overvoltage and secondary arc current <\/td>\n<\/tr>\n | ||||||
| 422<\/td>\n | K.4 SFO and Beat frequency overvoltage limited by neutral arrester <\/td>\n<\/tr>\n | ||||||
| 423<\/td>\n | K.5 SFO and FFO due to SR de-energization K.6 Limitation of TOV by Controllable SR K.7 Insulation coordination of the SR and neutral grounding reactor K.8 Self-excitation TOV of synchronous generator <\/td>\n<\/tr>\n | ||||||
| 424<\/td>\n | Annex L (informative) Calculation of lightning stroke rate and lightning outage rate L.1 General L.2 Description in CIGRE [37] <\/td>\n<\/tr>\n | ||||||
| 425<\/td>\n | L.3 Flash program in IEEE [49] L.4 [Case Study] Calculation of Lightning Stroke Rate and Lightning Outage Rate (Appendix D in CIGRE TB 839 [37]) L.4.1 Basic flow of calculation method Figure L.1 \u2013 Outline of the CIGRE method for lightning performance of an overhead line <\/td>\n<\/tr>\n | ||||||
| 427<\/td>\n | Figure L.2 \u2013 Flowchart to calculate lightning outage rate of transmission lines <\/td>\n<\/tr>\n | ||||||
| 428<\/td>\n | L.4.2 Comparison of Calculation Results with Observations Figure L.3 \u2013 Typical conductor arrangements of large-scale transmission lines Figure L.4 \u2013 Lightning stroke rate to power lines -calculations and observations- <\/td>\n<\/tr>\n | ||||||
| 429<\/td>\n | Figure L.5 \u2013 Lightning outage rate -calculations and observations- <\/td>\n<\/tr>\n | ||||||
| 430<\/td>\n | Bibliography <\/td>\n<\/tr>\n<\/table>\n","protected":false},"excerpt":{"rendered":" Tracked Changes. Insulation co-ordination – Application guidelines<\/b><\/p>\n |