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BS EN IEC 60071-2:2023 – TC

BS EN IEC 60071-2:2023 – TC

$280.87

Tracked Changes. Insulation co-ordination – Application guidelines

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BSI 2023 435
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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.

PDF Catalog

PDF Pages PDF Title
1 30481456
246 A-30387030
247 undefined
250 Annex ZA (normative)Normative references to international publicationswith their corresponding European publications
251 English
CONTENTS
258 FOREWORD
260 1 Scope
2 Normative references
261 3 Terms, definitions, abbreviated terms and symbols
3.1 Terms and definitions
3.2 Abbreviated terms
262 3.3 Symbols
267 4 Concepts governing the insulation co-ordination
268 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
269 5.2.2 Metal-oxide surge arresters without gaps (MOSA)
271 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
275 5.3.3 Slow-front overvoltages
277 Figures
Figure 1 – Range of 2 % slow-front overvoltages at the receiving end due to line energization and re-energization [27]
278 Figure 2 – Ratio between the 2 % values of slow-front overvoltages phase-to-phase and phase-to-earth [28], [29]
281 5.3.4 Fast-front overvoltages
285 5.3.5 Very-fast-front overvoltages
Figure 3 – Diagram for surge arrester connection to the protected object
286 5.4 Determination of representative overvoltages by detailed simulations
5.4.1 General overview
5.4.2 Temporary overvoltages
287 5.4.3 Slow-front overvoltages
288 5.4.4 Fast-front overvoltages
291 Figure 4 – Modelling of transmission lines and substations/power stations
292 5.4.5 Very-fast-front overvoltages
293 6 Co-ordination withstand voltage
6.1 Insulation strength characteristics
6.1.1 General
294 6.1.2 Influence of polarity and overvoltage shapes
295 6.1.3 Phase-to-phase and longitudinal insulation
296 6.1.4 Influence of weather conditions on external insulation
6.1.5 Probability of disruptive discharge of insulation
298 6.2 Performance criterion
6.3 Insulation co-ordination procedures
6.3.1 General
299 6.3.2 Insulation co-ordination procedures for continuous (power-frequency) voltage and temporary overvoltage
300 6.3.3 Insulation co-ordination procedures for slow-front overvoltages
Figure 5 – Distributive discharge probability of self-restoring insulation described on a linear scale
301 Figure 6 – Disruptive discharge probability of self-restoring insulation described on a Gaussian scale
Figure 7 – Evaluation of deterministic co-ordination factor Kcd
302 Figure 8 – Evaluation of the risk of failure
304 6.3.4 Insulation co-ordination procedures for fast-front overvoltages
Figure 9 – Risk of failure of external insulation for slow-front overvoltages as a function of the statistical co-ordination factor Kcs
305 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
306 7.2.2 Altitude correction
307 7.3 Safety factors
7.3.1 General
Figure 10 – Dependence of exponent m on the co-ordination switching impulse withstand voltage
308 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)
309 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
310 8.2 Test conversion factors
8.2.1 Range I
8.2.2 Range II
Tables
Table 1 – Test conversion factors for range I, to convert required SIWV to SDWV and LIWV
311 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 – Test conversion factors for range II to convert required SDWV to SIWV
312 8.3.4 Mixed insulation
Table 3 – Selectivity of test procedures B and C of IEC 60060-1
313 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 – Probability P of an equipment to pass the test dependent on the difference K between the actual and the rated impulse withstand voltage
314 9 Special considerations for apparatus and transmission line
9.1 Overhead line
9.1.1 General
315 9.1.2 Insulation co-ordination for operating voltages and temporary overvoltages
9.1.3 Insulation co-ordination for slow-front overvoltages
316 9.1.4 Insulation co-ordination for fast-front overvoltages
317 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
318 9.2.4 Insulation co-ordination for fast-front overvoltages
9.2.5 Overvoltage protection of cable lines
319 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
320 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 – Example of a schematic substation layout used for the overvoltage stress location
321 9.4.2 Insulation co-ordination for overvoltages
324 Annexes
Annex A (informative) Determination of temporary overvoltages due to earth faults
325 Figure A.1 – Earth fault factor k on a base of X0/X1 for R1/X1 = Rf = 0
Figure A.2 – Relationship between R0/X1 and X0/X1 for constant values of earth fault factor k where R1 = 0
326 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
327 Figure A.5 – Relationship between R0/X1 and X0/X1 for constant values of earth fault factor k where R1 = 2X1
328 Annex B (informative) Weibull probability distributions
B.1 General remarks
329 B.2 Disruptive discharge probability of external insulation
331 Table B.1 – Breakdown voltage versus cumulative flashover probability – Single insulation and 100 parallel insulations
332 B.3 Cumulative frequency distribution of overvoltages
334 Figure B.1 – Conversion chart for the reduction of the withstand voltage due to placing insulation configurations in parallel
335 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 – Probability density and cumulative distribution for derivation of the representative overvoltage phase-to-earth
338 C.3 Probability distribution of the representative amplitude of the prospective overvoltage phase-to-phase
339 C.4 Insulation characteristic
342 C.5 Numerical example
343 Figure C.2 – Example for bivariate phase-to-phase overvoltage curves with constant probability density and tangents giving the relevant 2 % values
344 Figure C.3 – Principle of the determination of the representative phase-to-phase overvoltage Upre
345 Figure C.4 – Schematic phase-phase-earth insulation configuration
Figure C.5 – Description of the 50 % switching impulse flashover voltage ofa phase-phase-earth insulation
346 Figure C.6 – 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
347 Annex D (informative) Transferred overvoltages in transformers
D.1 General remarks
348 D.2 Transferred temporary overvoltages
D.3 Capacitively transferred surges
350 D.4 Inductively transferred surges
352 Figure D.1 – Distributed capacitances of the windings of a transformer and the equivalent circuit describing the windings
353 Figure D.2 – Values of factor J describing the effect of the winding connections on the inductive surge transference
354 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
355 E.2.2 Self-protection of substation
Table E.1 – Corona damping constant Kco
356 E.3 Estimation of the representative lightning overvoltage amplitude
E.3.1 General
E.3.2 Shielding penetration
357 E.3.3 Back flashovers
359 E.4 Simplified approach
361 E.5 Assumed maximum value of the representative lightning overvoltage
Table E.2 – Factor A for various overhead lines
363 Annex F (informative) Calculation of air gap breakdown strength from experimental data
F.1 General
F.2 Insulation response to power-frequency voltages
364 F.3 Insulation response to slow-front overvoltages
365 F.4 Insulation response to fast-front overvoltages
367 Table F.1 – Typical gap factors K for switching impulse breakdown phase-to-earth (according to [1] and [4])
368 Table F.2 – Gap factors for typical phase-to-phase geometries
369 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
370 G.2.2 Part 1: no special operating conditions
376 Table G.1 – Summary of minimum required withstand voltages obtained for the example shown in G.2.2
377 G.2.3 Part 2: influence of capacitor switching at station 2
378 Table G.2 – Summary of required withstand voltages obtained for the example shown in G.2.3
379 G.2.4 Part 3: flow charts related to the example of Clause G.2
384 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
385 G.3.3 Step 2: determination of the co-ordination withstand voltages – values of Ucw
386 G.3.4 Step 3: determination of the required withstand voltages – values of Urw
387 G.3.5 Step 4: conversion to switching impulse withstand voltages (SIWV)
388 G.3.6 Step 5: selection of standard insulation levels
G.3.7 Considerations relative to phase-to-phase insulation co-ordination
389 G.3.8 Phase-to-earth clearances
390 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
391 G.4.2 Step 1: determination of the representative overvoltages – values of Urp
G.4.3 Step 2: determination of the co-ordination withstand voltages – values of Ucw
392 G.4.4 Step 3: determination of required withstand voltages – values of Urw
393 G.4.5 Step 4: conversion to standard short-duration power-frequency and lightning impulse withstand voltages
394 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
395 Table G.3 – Values related to the insulation co-ordination procedure for the example in G.4
396 Annex H (informative) Atmospheric correction – Altitude correction application example
H.1 General principles
H.1.1 Atmospheric correction in standard tests
397 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
398 Figure H.2 – Principal task of the atmospheric correction in insulation co-ordination according to IEC 60071-1
399 H.2 Atmospheric correction in insulation co-ordination
H.2.1 Factors for atmospheric correction
H.2.2 General characteristics for moderate climates
400 H.2.3 Special atmospheric conditions
401 H.2.4 Altitude dependency of air pressure
Figure H.3 – Comparison of atmospheric correction δ × kh with relative air pressure p/p0 for various weather stations around the world
402 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
403 H.3.2 Principle of altitude correction
404 H.3.3 Altitude correction for standard equipment operating at altitudes up to 1 000 m
Figure H.5 – Principle of altitude correction: decreasing withstand voltage U10 of equipment with increasing altitude
405 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
406 H.4.2 Derivation of exponent m for switching impulse voltage
408 H.4.3 Derivation of exponent m for critical switching impulse voltage
Figure H.6 – Sets of m-curves for standard switching impulse voltage including the variations in altitude for each gap factor
Figure H.7 – Exponent m for standard switching impulse voltage for selected gap factors covering altitudes up to 4 000 m
409 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
410 Figure H.10 – 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 – Comparison of functional expressions of Figure 10 with the selected parameters from the derivation of m-curves with critical switching impulse
411 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
412 I.3.2 Evaluation of overvoltage shape
I.4 Evaluation method for transformer
I.4.1 Experiments
413 I.4.2 Evaluation of overvoltage shape
Figure I.1 – Examples of lightning overvoltage shapes
414 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
415 Figure I.4 – Shape evaluation flow for GIS and transformer
416 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)
417 Figure I.7 – Application to transformer lightning overvoltage
Table I.2 – Evaluation of lightning overvoltage in the transformer of 500 kV system
418 Annex J (informative) Insulation co-ordination for very-fast-front overvoltages in UHV substations
J.1 General
J.2 Influence of disconnector design
419 J.3 Insulation co-ordination for VFFO
420 Figure J.1 – Insulation co-ordination for very-fast-front overvoltages
421 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
422 K.4 SFO and Beat frequency overvoltage limited by neutral arrester
423 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
424 Annex L (informative) Calculation of lightning stroke rate and lightning outage rate
L.1 General
L.2 Description in CIGRE [37]
425 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 – Outline of the CIGRE method for lightning performance of an overhead line
427 Figure L.2 – Flowchart to calculate lightning outage rate of transmission lines
428 L.4.2 Comparison of Calculation Results with Observations
Figure L.3 – Typical conductor arrangements of large-scale transmission lines
Figure L.4 – Lightning stroke rate to power lines -calculations and observations-
429 Figure L.5 – Lightning outage rate -calculations and observations-
430 Bibliography

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BS EN IEC 60071-2:2023 - TC
$280.87