BS EN IEC 60071-2:2018
$215.11
Insulation co-ordination – Application guidelines
| Published By | Publication Date | Number of Pages |
| BSI | 2018 | 162 |
IEC 60071-2:2018 is now available as /2 which contains the International Standard and its Redline version, showing all changes of the technical content compared to the previous edition.
IEC 60071-2:2018 constitutes application guidelines and deals with the selection of insulation levels of equipment or installations for three-phase electrical systems. It gives 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. It covers three-phase systems with nominal voltages above 1 kV. It has the status of a horizontal standard in accordance with IEC Guide 108. This edition includes the following significant technical changes with respect to the previous edition: a) the annex on clearance in air to assure a specified impulse withstand voltage installation is deleted because the annex in IEC 60071-1 is overlapped; b) 4.2 and 4.3 on surge arresters are updated; c) 4.3.5 on very-fast-front overvoltages is revised. Annex J on insulation co-ordination for very-fast-front overvoltages in UHV substations is added; d) Annex H on atmospheric correction – altitude correction is added. e) Annex I on evaluation method of non-standard lightning overvoltage shape is added.
PDF Catalog
| PDF Pages | PDF Title |
|---|---|
| 2 | undefined |
| 6 | English CONTENTS |
| 12 | FOREWORD |
| 14 | 1 Scope 2 Normative references |
| 15 | 3 Terms, definitions, abbreviated terms and symbols 3.1 Terms and definitions 3.2 Abbreviated terms 3.3 Symbols |
| 20 | 4 Representative voltage stresses in service 4.1 Origin and classification of voltage stresses |
| 21 | 4.2 Characteristics of overvoltage protection devices 4.2.1 General remarks 4.2.2 Metal-oxide surge arresters without gaps (MOSA) |
| 23 | 4.2.3 Line surge arresters (LSA) for overhead transmission and distribution lines 4.3 Representative voltages and overvoltages 4.3.1 Continuous (power-frequency) voltage |
| 24 | 4.3.2 Temporary overvoltages |
| 27 | 4.3.3 Slow-front overvoltages |
| 29 | Figures Figure 1 – Range of 2 % slow-front overvoltages at the receiving end due to line energization and re-energization |
| 30 | Figure 2 – Ratio between the 2 % values of slow-front overvoltages phase-to-phase and phase-to-earth |
| 33 | 4.3.4 Fast-front overvoltages |
| 37 | 4.3.5 Very-fast-front overvoltages [13] Figure 3 – Diagram for surge arrester connection to the protected object |
| 38 | 5 Co-ordination withstand voltage 5.1 Insulation strength characteristics 5.1.1 General |
| 39 | 5.1.2 Influence of polarity and overvoltage shapes |
| 40 | 5.1.3 Phase-to-phase and longitudinal insulation 5.1.4 Influence of weather conditions on external insulation |
| 41 | 5.1.5 Probability of disruptive discharge of insulation |
| 42 | 5.2 Performance criterion |
| 43 | 5.3 Insulation co-ordination procedures 5.3.1 General |
| 44 | 5.3.2 Insulation co-ordination procedures for continuous (power-frequency) voltage and temporary overvoltage 5.3.3 Insulation co-ordination procedures for slow-front overvoltages |
| 45 | Figure 4 – Distributive discharge probability of self-restoring insulation described on a linear scale Figure 5 – Disruptive discharge probability of self-restoring insulation described on a Gaussian scale |
| 46 | Figure 6 – Evaluation of deterministic co-ordination factor Kcd |
| 47 | Figure 7 – Evaluation of the risk of failure |
| 49 | 5.3.4 Insulation co-ordination procedures for fast-front overvoltages Figure 8 – Risk of failure of external insulation for slow-front overvoltages as a function of the statistical co-ordination factor Kcs |
| 50 | 6 Required withstand voltage 6.1 General remarks 6.2 Atmospheric correction 6.2.1 General remarks 6.2.2 Altitude correction |
| 51 | Figure 9 – Dependence of exponent m on the co-ordination switching impulse withstand voltage |
| 52 | 6.3 Safety factors 6.3.1 General 6.3.2 Ageing 6.3.3 Production and assembly dispersion 6.3.4 Inaccuracy of the withstand voltage |
| 53 | 6.3.5 Recommended safety factors (Ks) 7 Standard withstand voltage and testing procedures 7.1 General remarks 7.1.1 Overview 7.1.2 Standard switching impulse withstand voltage |
| 54 | 7.1.3 Standard lightning impulse withstand voltage 7.2 Test conversion factors 7.2.1 Range I |
| 55 | 7.2.2 Range II 7.3 Determination of insulation withstand by type tests 7.3.1 Test procedure dependency upon insulation type Tables Table 1 – Test conversion factors for range I, to convert required SIWV to SDWV and LIWV Table 2 – Test conversion factors for range II to convert required SDWV to SIWV |
| 56 | 7.3.2 Non-self-restoring insulation 7.3.3 Self-restoring insulation 7.3.4 Mixed insulation |
| 57 | 7.3.5 Limitations of the test procedures Figure 10 – Probability P of an equipment to pass the test dependent onthe difference K between the actual and the rated impulse withstand voltage Table 3 – Selectivity of test procedures B and C of IEC 60060-1 |
| 58 | 7.3.6 Selection of the type test procedures 7.3.7 Selection of the type test voltages |
| 59 | 8 Special considerations for overhead lines 8.1 General remarks 8.2 Insulation co-ordination for operating voltages and temporary overvoltages 8.3 Insulation co-ordination for slow-front overvoltages 8.3.1 General |
| 60 | 8.3.2 Earth-fault overvoltages 8.3.3 Energization and re-energization overvoltages 8.4 Insulation co-ordination for lightning overvoltages 8.4.1 General 8.4.2 Distribution lines |
| 61 | 8.4.3 Transmission lines 9 Special considerations for substations 9.1 General remarks 9.1.1 Overview 9.1.2 Operating voltage 9.1.3 Temporary overvoltage Figure 11 – Example of a schematic substation layout used for the overvoltage stress location |
| 62 | 9.1.4 Slow-front overvoltages 9.1.5 Fast-front overvoltages 9.2 Insulation co-ordination for overvoltages 9.2.1 Substations in distribution systems with Um up to 36 kV in range I |
| 63 | 9.2.2 Substations in transmission systems with Um between 52,5 kV and 245 kV in range I |
| 64 | 9.2.3 Substations in transmission systems in range II |
| 65 | Annexes Annex A (informative) Determination of temporary overvoltages due to earth faults |
| 66 | Figure A.1 – Earth fault factor k on a base of X0/X1 for R1/X1 = R = 0 Figure A.2 – Relationship between R0/X1 and X0/X1 for constant values of earth fault factor k where R1 = 0 |
| 67 | Figure A.3 – Relationship between R0/X1 and X0/X1 for constant values of earth fault factor k where R1 = 0,5 X1 Figure A.4 – Relationship between R0/X1 and X0/X1 for constant values of earth fault factor k where R1 = X1 |
| 68 | Figure A.5 – Relationship between R0/X1 and X0/X1 for constant values of earth fault factor k where R1 = 2X1 |
| 69 | Annex B (informative) Weibull probability distributions B.1 General remarks |
| 70 | B.2 Disruptive discharge probability of external insulation |
| 71 | Table B.1 – Breakdown voltage versus cumulative flashover probability –Single insulation and 100 parallel insulations |
| 72 | B.3 Cumulative frequency distribution of overvoltages |
| 74 | Figure B.1 – Conversion chart for the reduction of the withstand voltage due to placing insulation configurations in parallel |
| 75 | 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 C.3 Probability distribution of the representative amplitude of the prospective overvoltage phase-to-phase |
| 77 | C.4 Insulation characteristic |
| 79 | C.5 Numerical example |
| 81 | Figure C.1 – Example for bivariate phase-to-phase overvoltage curves with constant probability density and tangents giving the relevant 2 % values |
| 82 | Figure C.2 – Principle of the determination of the representative phase-to-phase overvoltage Upre |
| 83 | Figure C.3 – Schematic phase-phase-earth insulation configuration Figure C.4 – Description of the 50 % switching impulse flashover voltage ofa phase-phase-earth insulation |
| 84 | Figure C.5 – Inclination angle of the phase-to-phase insulation characteristicin range “b” dependent on the ratio of the phase-phase clearance Dto the height Ht above earth |
| 85 | Annex D (informative) Transferred overvoltages in transformers D.1 General remarks |
| 86 | D.2 Transferred temporary overvoltages D.3 Capacitively transferred surges |
| 88 | D.4 Inductively transferred surges |
| 90 | Figure D.1 – Distributed capacitances of the windings of a transformer and the equivalent circuit describing the windings |
| 91 | Figure D.2 – Values of factor J describing the effect of the winding connections on the inductive surge transference |
| 92 | Annex E (informative) Lightning overvoltages E.1 General remarks E.2 Determination of the limit distance (Xp) E.2.1 Protection with arresters in the substation |
| 93 | E.2.2 Self-protection of substation Table E.1 – Corona damping constant Kco |
| 94 | E.3 Estimation of the representative lightning overvoltage amplitude E.3.1 General E.3.2 Shielding penetration |
| 95 | E.3.3 Back flashovers |
| 97 | E.4 Simplified method |
| 98 | Table E.2 – Factor A for various overhead lines |
| 99 | E.5 Assumed maximum value of the representative lightning overvoltage |
| 100 | Annex F (informative) Calculation of air gap breakdown strength from experimental data F.1 General F.2 Insulation response to power-frequency voltages |
| 101 | F.3 Insulation response to slow-front overvoltages |
| 102 | F.4 Insulation response to fast-front overvoltages |
| 104 | Table F.1 – Typical gap factors K for switching impulse breakdown phase-to-earth (according to [1] and [4]) |
| 105 | Table F.2 – Gap factors for typical phase-to-phase geometries |
| 106 | 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 |
| 107 | G.2.2 Part 1: no special operating conditions |
| 113 | Table G.1 – Summary of minimum required withstand voltages obtained for the example shown in G.2.2 |
| 114 | G.2.3 Part 2: influence of capacitor switching at station 2 |
| 115 | Table G.2 – Summary of required withstand voltages obtained for the example shown in G.2.3 |
| 116 | G.2.4 Part 3: flow charts related to the example of Clause G.2 |
| 121 | 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 – values of Urp |
| 122 | G.3.3 Step 2: determination of the co-ordination withstand voltages – values of Ucw |
| 123 | G.3.4 Step 3: determination of the required withstand voltages – values of Urw |
| 124 | G.3.5 Step 4: conversion to switching impulse withstand voltages (SIWV) G.3.6 Step 5: selection of standard insulation levels |
| 125 | G.3.7 Considerations relative to phase-to-phase insulation co-ordination |
| 126 | G.3.8 Phase-to-earth clearances G.3.9 Phase-to-phase clearances |
| 127 | G.4 Numerical example for substations in distribution systems with Um up to 36 kV in range I G.4.1 General G.4.2 Step 1: determination of the representative overvoltages – values of Urp |
| 128 | G.4.3 Step 2: determination of the co-ordination withstand voltages – values of Ucw |
| 129 | G.4.4 Step 3: determination of required withstand voltages – values of Urw |
| 130 | G.4.5 Step 4: conversion to standard short-duration power-frequency and lightning impulse withstand voltages G.4.6 Step 5: selection of standard withstand voltages |
| 131 | G.4.7 Summary of insulation co-ordination procedure for the example of Clause G.4 |
| 132 | Table G.3 – Values related to the insulation co-ordination procedure for the example in G.4 |
| 133 | Annex H (informative)Atmospheric correction – Altitude correction H.1 General principles H.1.1 Atmospheric correction in standard tests |
| 134 | H.1.2 Task of atmospheric correction in insulation co-ordination Figure H.1 – Principle of the atmospheric correction during test of a specified insulation level according to the procedure of IEC 60060-1 |
| 135 | Figure H.2 – Principal task of the atmospheric correctionin insulation co-ordination according to IEC 60071-1 |
| 136 | H.2 Atmospheric correction in insulation co-ordination H.2.1 Factors for atmospheric correction H.2.2 General characteristics for moderate climates |
| 137 | H.2.3 Special atmospheric conditions Figure H.3 – Comparison of atmospheric correction δ × kh with relative air pressure p/p0 for various weather stations around the world |
| 138 | H.2.4 Altitude dependency of air pressure |
| 139 | H.3 Altitude correction H.3.1 Definition of the altitude correction factor Figure H.4 – Deviation of simplified pressure calculation by exponential function in this document from the temperature dependent pressure calculation of ISO 2533 |
| 140 | H.3.2 Principle of altitude correction Figure H.5 – Principle of altitude correction: decreasing withstand voltage U10 of equipment with increasing altitude |
| 141 | H.3.3 Standard equipment operating at altitudes up to 1 000 m H.3.4 Equipment operating at altitudes above 1 000 m |
| 142 | H.4 Selection of the exponent m H.4.1 General H.4.2 Derivation of exponent m for switching impulse voltage |
| 144 | Figure H.6 – Sets of m-curves for standard switching impulse voltage including the variations in altitude for each gap factor |
| 145 | H.4.3 Derivation of exponent m for critical switching impulse voltage Figure H.7 – Exponent m for standard switching impulse voltage for selected gap factors covering altitudes up to 4 000 m |
| 146 | Figure H.8 – Sets of m-curves for critical switching impulse voltage including the variations in altitude for each gap factor Figure H.9 – Exponent m for critical switching impulse voltage for selected gap factors covering altitudes up to 4 000 m |
| 147 | Figure H.10 – Accordance of m-curves from Figure 9 with determination ofexponent m by means of critical switching impulse voltage for selected gap factors and altitudes Table H.1 – Comparison of functional expressions of Figure 9 with the selected parameters from the derivation of m-curves with critical switching impulse |
| 148 | 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 |
| 149 | I.3.2 Evaluation of overvoltage shape I.4 Evaluation method for transformer I.4.1 Experiments I.4.2 Evaluation of overvoltage shape |
| 151 | Figure I.1 – Examples of lightning overvoltage shapes |
| 152 | Figure I.2 – Example of insulation characteristics with respect to lightning overvoltages of the SF6 gas gap (Shape E) Figure I.3 – Calculation of duration time Td Table I.1 – Evaluation of the lightning overvoltage in the GIS of UHV system |
| 153 | Figure I.4 – Shape evaluation flow for GIS and transformer |
| 154 | Figure I.5 – Application to GIS lightning overvoltage Figure I.6 – Example of insulation characteristics with respect to lightning overvoltage of the turn-to-turn insulation (Shape C) |
| 155 | Figure I.7 – Application to transformer lightning overvoltage Table I.2 – Evaluation of lightning overvoltage in the transformer of 500 kV system |
| 156 | Annex J (informative) Insulation co-ordination for very-fast-front overvoltages in UHV substations J.1 General J.2 Influence of disconnector design |
| 157 | J.3 Insulation co-ordination for VFFO |
| 158 | Figure J.1 – Insulation co-ordination for very-fast-front overvoltages |
| 159 | Bibliography |
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