FprEN IEC 60071-12:2022

Insulation co-ordination - Part 12: Application guidelines for LCC HVDC converter stations

Isolationskoordination für HVDC Systeme – Teil 12: Anwendungsrichtlinien für Stromrichterstationen mit Stromzwischenkreis-Konverter (LCC)

Coordination de l’isolement - Partie 12: Lignes directrices en matière d’application pour stations de conversion à courant continu haute tension (CCHT) équipées de convertisseurs commutés par le réseau (LCC)

Koordinacija izolacije - 12. del: Smernice za uporabo LCC visokonapetostnih enosmernih (HVDC) pretvorniških postaj

General Information

• Status: Not Published
• ICS: 29.080.30 - Insulation systems
• Technical Committee: CLC/TC 99X - Power installations exceeding 1 kV a.c. (1,5 kV d.c.)
• Drafting Committee: IEC/TC 99 - IEC_TC_99
• Ref Project: kSIST prEN IEC 60071-12:2022 - Insulation co-ordination - Part 12: Application guidelines for LCC HVDC converter stations

Standards Content (sample)

SLOVENSKI STANDARD
oSIST prEN IEC 60071-12:2021
01-november-2021
Koordinacija izolacije - 12. del: Smernice za uporabo LCC visokonapetostnih
enosmernih (HVDC) pretvorniških postaj

Insulation co-ordination - Part 12: Application guidelines for LCC HVDC converter

stations
Ta slovenski standard je istoveten z: prEN IEC 60071-12:2021
ICS:
29.080.30 Izolacijski sistemi Insulation systems
oSIST prEN IEC 60071-12:2021 en

2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.

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oSIST prEN IEC 60071-12:2021
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oSIST prEN IEC 60071-12:2021
99/326/CDV
COMMITTEE DRAFT FOR VOTE (CDV)
PROJECT NUMBER:
IEC 60071-12 ED1
DATE OF CIRCULATION: CLOSING DATE FOR VOTING:
2021-09-24 2021-12-17
SUPERSEDES DOCUMENTS:
99/308/CD, 99/315/CC

IEC TC 99 : INSULATION CO-ORDINATION AND SYSTEM ENGINEERING OF HIGH VOLTAGE ELECTRICAL POWER INSTALLATIONS ABOVE

1,0 KV AC AND 1,5 KV DC
SECRETARIAT: SECRETARY:
Australia Ms Erandi Chandrasekare
OF INTEREST TO THE FOLLOWING COMMITTEES: PROPOSED HORIZONTAL STANDARD:
TC 8,SC 22F,TC 115
Other TC/SCs are requested to indicate their interest, if any, in
this CDV to the secretary.
FUNCTIONS CONCERNED:
EMC ENVIRONMENT QUALITY ASSURANCE SAFETY

SUBMITTED FOR CENELEC PARALLEL VOTING NOT SUBMITTED FOR CENELEC PARALLEL VOTING

Attention IEC-CENELEC parallel voting
The attention of IEC National Committees, members of
CENELEC, is drawn to the fact that this Committee Draft
for Vote (CDV) is submitted for parallel voting.
The CENELEC members are invited to vote through the
CENELEC online voting system.

This document is still under study and subject to change. It should not be used for reference purposes.

Recipients of this document are invited to submit, with their comments, notification of any relevant patent rights of which

they are aware and to provide supporting documentation.
TITLE:

Insulation co-ordination - Part 12: Application guidelines for LCC HVDC converter stations

PROPOSED STABILITY DATE: 2028
NOTE FROM TC/SC OFFICERS:

Copyright © 2021 International Electrotechnical Commission, IEC. All rights reserved. It is permitted to download this

electronic file, to make a copy and to print out the content for the sole purpose of preparing National Committee positions.

You may not copy or "mirror" the file or printed version of the document, or any part of it, for any other purpose without

permission in writing from IEC.
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oSIST prEN IEC 60071-12:2021
IEC CDV 60071-12 © IEC 2021 – 2 – 99/326/CDV
1 CONTENTS

3 FOREWORD ........................................................................................................................... 5

4 1 General ........................................................................................................................... 8

5 1.1 Scope ..................................................................................................................... 8

6 1.2 Additional background ............................................................................................ 8

7 2 Normative references ...................................................................................................... 8

8 3 Terms, definitions, symbols and abbreviations ................................................................. 9

9 3.1 Terms and definition ............................................................................................... 9

10 3.2 Symbols and abbreviation ....................................................................................... 9

11 3.2.1 General ........................................................................................................... 9

12 3.2.2 Subscripts ..................................................................................................... 10

13 3.2.3 Letter symbols ............................................................................................... 10

14 3.2.4 Abbreviations................................................................................................. 10

15 4 Typical LCC HVDC converter station schemes .............................................................. 11

16 5 Voltages and overvoltages in service ............................................................................. 13

17 5.1 Continuous operating voltages at various locations in the converter station .......... 13

18 5.2 Peak continuous operating voltage (PCOV) and crest continuous operating

19 voltage (CCOV) .................................................................................................... 17

20 5.3 Sources and types of overvoItages ....................................................................... 18

21 5.4 Temporary overvoltage ......................................................................................... 19

22 5.4.1 General ......................................................................................................... 19

23 5.4.2 Temporary overvoltage on the a.c. side ......................................................... 19

24 5.4.3 Temporary overvoltages on the d.c. side ....................................................... 20

25 5.5 Slow-front overvoltages ........................................................................................ 20

26 5.5.1 General ......................................................................................................... 20

27 5.5.2 Slow-front overvoltages on the a.c. side ........................................................ 20

28 5.5.3 Slow-front overvoltages on the d.c. side ........................................................ 21

29 5.6 Fast-front, very-fast-front and steep-front overvoltages ......................................... 21

30 6 Arrester characteristics and stresses ............................................................................. 22

31 6.1 Arrester characteristics ......................................................................................... 22

32 6.2 Arrester specification ............................................................................................ 23

33 6.3 Arrester stresses .................................................................................................. 24

34 6.3.1 General ......................................................................................................... 24

35 6.3.2 AC bus arrester (A) ........................................................................................ 24

36 6.3.3 AC filter arrester (FA) .................................................................................... 25

37 6.3.4 Transformer valve winding arresters (T) ........................................................ 25

38 6.3.5 Valve arrester (V) .......................................................................................... 25

39 6.3.6 Bridge arrester (B) ......................................................................................... 28

40 6.3.7 Converter unit arrester (C) ............................................................................. 29

41 6.3.8 Mid-point d.c. bus arrester (M) ....................................................................... 29

42 6.3.9 Converter unit d.c. bus arrester (CB) ............................................................. 29

43 6.3.10 DC bus and d.c. line/cable arrester (DB and DL/DC) ...................................... 30

44 6.3.11 Neutral bus arrester (E, EL, EM in Figure 3, EB, E1, EL, EM in Figure 1) ...... 30

45 6.3.12 DC reactor arrester (DR) ............................................................................... 31

46 6.3.13 DC filter arrester (FD) .................................................................................... 32

47 6.3.14 Earth electrode station arrester ..................................................................... 32

48 6.4 Protection strategy ................................................................................................ 32

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49 6.4.1 General ......................................................................................................... 32

50 6.4.2 Insulation directly protected by a single arrester ............................................ 32

51 6.4.3 Insulation protected by more than one arrester in series ................................ 32

52 6.4.4 Valve side neutral point of transformers ......................................................... 33

53 6.4.5 Insulation between phase conductors of the converter transformer ................ 33

54 6.4.6 Summary of protection strategy ..................................................................... 33

55 6.5 Summary of events and stresses .......................................................................... 35

56 7 Design procedure of insulation co-ordination ................................................................. 36

57 7.1 General ................................................................................................................. 36

58 7.2 Arrester requirements ........................................................................................... 36

59 7.3 Representative overvoltages (U ) ........................................................................ 37

60 7.4 Determination of the co-ordination withstand voltages (U )................................. 39

61 7.5 Determination of the required withstand voltages (U ) ........................................ 39

62 7.6 Determination of the specified withstand voltage (U ) .......................................... 39

63 8 Study tools and system modelling .................................................................................. 39

64 8.1 General ................................................................................................................. 39

65 8.2 Study approach and tooIs ..................................................................................... 39

66 8.3 System details ...................................................................................................... 40

67 8.3.1 Modelling and system representation ............................................................. 40

68 8.3.2 AC network and a.c. side of the LCC HVDC converter station ........................ 41

69 8.3.3 DC overhead line/cable and earth electrode line details ................................. 42

70 8.3.4 DC side of an LCC HVDC converter station details ........................................ 42

71 Annex A (informative) Example of insulation co-ordination for LCC HVDC converter

72 stations ......................................................................................................................... 44

73 A.1 Introduction ........................................................................................................... 44

74 A.2 Example for LCC HVDC converter station in a pole with one 12-pulse

75 converter .............................................................................................................. 44

76 A.2.1 Arrester protective scheme ............................................................................ 44

77 A.2.2 Arrester stresses, protection and insulation levels ......................................... 44

78 A.2.3 Transformer valve side withstand voltages .................................................... 48

79 A.2.4 Air-insulated smoothing reactors withstand voltages ...................................... 49

80 A.2.5 Results .......................................................................................................... 50

81 A.3 Example for LCC HVDC converter station in a pole with two 12-pulse

82 converters in series............................................................................................... 52

83 A.3.1 Arrester protective scheme ............................................................................ 52

84 A.3.2 Arrester stresses, protection and insulation levels ......................................... 53

85 A.3.3 Transformer valve side withstand voltages .................................................... 57

86 A.3.4 Smoothing reactor withstand voltages............................................................ 58

87 A.3.5 Results .......................................................................................................... 60

88 Bibliography .......................................................................................................................... 62

90 Figure 1 – Possible arrester locations in a pole with two 12-pulse converters in series ......... 12

91 Figure 2 – Possible arrester locations for a back-to-back converter station ........................... 13

92 Figure 3 – LCC HVDC converter station in a pole with one 12-pulse converter ...................... 14

93 Figure 4 – Continuous operating voltages at various locations (location identification

94 according to Figure 3) ........................................................................................................... 16

95 Figure 5 – Operating voltage of a valve arrester (V), rectifier operation ................................. 18

96 Figure 6 – Operating voltage of a mid-point arrester (M), rectifier operation .......................... 18

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97 Figure 7 – Operating voltage of a converter bus arrester (CB), rectifier operation ................. 18

98 Figure 8 – One pole of an LCC HVDC converter station ........................................................ 41

99 Figure A.1 – AC and DC arresters (LCC HVDC converter station in a pole with one 12-

100 pulse converter) .................................................................................................................... 51

101 Figure A.2 – Valve arrester stresses for slow-front overvoltages from a.c. side ..................... 51

102 Figure A.3 – Arrester V2 stress for slow-front overvoltage from a.c. side .............................. 51

103 Figure A.4 – Valve arrester stresses for earth fault between valve and upper bridge

104 transformer bushing .............................................................................................................. 52

105 Figure A.5 – Arrester V1 stress for earth fault between valve and upper bridge

106 transformer bushing .............................................................................................................. 52

107 Figure A.6 – AC and DC arresters (LCC HVDC converter station in a pole with two 12-

108 pulse converters in series) .................................................................................................... 61

109

110 Table 1 – Symbol description ................................................................................................ 13

111 Table 2 – Arrester protection on the d.c. side: one 12-pulse converter (Figure 3) .................. 33

112 Table 3 – Arrester protection on the d.c. side: two 12-pulse converters in series

113 (Figure1) ............................................................................................................................... 34

114 Table 4 – Events stressing arresters: one 12-pulse converter (Figure 3) ............................... 35

115 Table 5 – Types of arrester stresses for different events: one 12-pulse converter

116 (Figure 3) .............................................................................................................................. 36

117 Table 6 – Arrester requirements ............................................................................................ 37

118 Table 7 – Representative overvoltages and required withstand voltages ............................... 37

119 Table 8 – Origin of overvoltages and associated frequency ranges ....................................... 40

120
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oSIST prEN IEC 60071-12:2021
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121 INTERNATIONAL ELECTROTECHNICAL COMMISSION
122 ____________
123
124 INSULATION CO-ORDINATION
125
126 Part 12: Application guidelines for LCC HVDC converter stations
127
128
129
130 FOREWORD

131 1) The International Electrotechnical Commission (IEC) is a worldwide organization for standardization comprising

132 all national electrotechnical committees (IEC National Committees). The object of IEC is to promote international

133 co-operation on all questions concerning standardization in the electrical and electronic fields. To this end and

134 in addition to other activities, IEC publishes International Standards, Technical Specifications, Technical Reports,

135 Publicly Available Specifications (PAS) and Guides (hereafter referred to as “IEC Publication(s)”). Their

136 preparation is entrusted to technical committees; any IEC National Committee interested in the subject dealt with

137 may participate in this preparatory work. International, governmental and non-governmental organizations liaising

138 with the IEC also participate in this preparation. IEC collaborates closely with the International Organization for

139 Standardization (ISO) in accordance with conditions determined by agreement between the two organizations.

140 2) The formal decisions or agreements of IEC on technical matters express, as nearly as possible, an international

141 consensus of opinion on the relevant subjects since each technical committee has representation from all

142 interested IEC National Committees.

143 3) IEC Publications have the form of recommendations for international use and are accepted by IEC National

144 Committees in that sense. While all reasonable efforts are made to ensure that the technical content of IEC

145 Publications is accurate, IEC cannot be held responsible for the way in which they are used or for any

146 misinterpretation by any end user.

147 4) In order to promote international uniformity, IEC National Committees undertake to apply IEC Publications

148 transparently to the maximum extent possible in their national and regional publications. Any divergence between

149 any IEC Publication and the corresponding national or regional publication shall be clearly indicated in the latter.

150 5) IEC itself does not provide any attestation of conformity. Independent certification bodies provide conformity

151 assessment services and, in some areas, access to IEC marks of conformity. IEC is not responsible for any

152 services carried out by independent certification bodies.

153 6) All users should ensure that they have the latest edition of this publication.

154 7) No liability shall attach to IEC or its directors, employees, servants or agents including individual experts and

155 members of its technical committees and IEC National Committees for any personal injury, property damage or

156 other damage of any nature whatsoever, whether direct or indirect, or for costs (including legal fees) and

157 expenses arising out of the publication, use of, or reliance upon, this IEC Publication or any other IEC

158 Publications.

159 8) Attention is drawn to the Normative references cited in this publication. Use of the referenced publications is

160 indispensable for the correct application of this publication.

161 9) Attention is drawn to the possibility that some of the elements of this IEC Publication may be the subject of patent

162 rights. IEC shall not be held responsible for identifying any or all such patent rights.

163 IEC 60071-12 has been prepared by IEC technical committee 99: Insulation co-ordination and

164 system engineering of high voltage electrical power installations above 1,0 kV AC and 1,5 kV

165 DC. It is an International Standard.

166 This International Standard and IEC 60071-11 'Definitions, principles and rules for HVDC

167 system' jointly replace IEC 60071-5 published in 2014.

168 The sections arrangement of this standard and corresponding section of IEC 60071-5: 2014 are

169 as follows,
IEC 60071-12 IEC 60071-5:2014
1 General 1
1.1 Scope 1.1
1.2 Additional background 1.2
2 Normative references 2
3 Terms, definitions, symbols and abbreviations -
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3 .1 Terms and definitions 3
3.2 Symbols and abbreviations 4
3.2.1 General 4.1
3.2.2 Subscripts 4.2
3.2.3 Letter symbols 4.3
3.2.4 Abbreviations 4.4
4 Typical LCC HVDC converter station schemes 5
5 Voltages and overvoltages in service 7
5.1 Continuous operating voltages at various locations in the 7.1
converter station
5.2 Peak continuous operating voltage (PCOV) and crest continuous 7.2
operating voltage (CCOV)
5.3 Sources and types of overvoItages 7.3
5.4 Temporary overvoltage 7.4
5.5 Slow-front overvoltages 7.5
5.6 Fast-front, very-fast-front and steep-front overvoltages 7.6
6 Arrester characteristics stresses 8
6.1 Arresters characteristics 8.1
6.2 Arresters specification 8.2
6.3 Arrester stresses 8.3
6.4 Protection strategy 8.4
6.5 Summary of events and stresses 8.5
7 Design procedure of insulation co-ordination 9
7.1 General 9.1
7.2 Arrester requirements 9.2
7.3 Representative overvoltages (U ) 9.4
7.4 Determination of the co-ordination withstand voltages 9.5
(U )
7.5 Determination of the required withstand voltages (U ) 9.6
7.6 Determination of the specified withstand voltage (U ) 9.7
8 Study tools and system modelling 10
8.1 General 10.1
8.2 Study approach and tools 10.2
8.3 System details 10.3

Annex A (informative) Example of insulation co-ordination for LCC Annex A (informative) Example

HVDC converter stations of insulation co-ordination for
conventional HVDC converters
170 The text of this International Standard is based on the following documents:
FDIS Report on voting
xx/xx/FDIS xx/xx/RVD

171 Full information on the voting for the approval of this International Standard can be found in the

172 report on voting indicated in the above table.

173 The language used for the development of this International Standard is English.

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174 This document was drafted in accordance with ISO/IEC Directives, Part 2, and developed in

175 accordance with ISO/IEC Directives, Part 1 and ISO/IEC Directives, IEC Supplement, available

176 at www.iec.ch/members_experts/refdocs. The main document types developed by IEC are

177 described in greater detail at http://www.iec.ch/standardsdev/publications.

178 The committee has decided that the contents of this document will remain unchanged until the

179 stability date indicated on the IEC website under webstore.iec.ch in the data related to the

180 specific document. At this date, the document will be
181 • reconfirmed,
182 • withdrawn,
183 • replaced by a revised edition, or
184 • amended.
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oSIST prEN IEC 60071-12:2021
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185 INSULATION CO-ORDINATION
186
187 Part 12: Application guidelines for LCC HVDC converter stations
188
189
190
191 1 General
192 1.1 Scope

193 This standard applies guidelines on the procedures for insulation co-ordination of line

194 commutated converter (LCC) stations for high-voltage direct current (HVDC) project, whose aim

195 is to give guidance for the determination of the specified withstand voltages for equipment.

196 The content of this document strictly follows the flow chart of the insulation co-ordination

197 process and give detailed information on the concepts governing the insulation co-ordination

198 process which leads to the establishment of the specified withstand voltage levels.

199 This document emphasizes the necessity of considering, at the very beginning, all origins, all

200 classes and all types of voltage stresses in service. At the end of the process, when the

201 selection of the specified withstand voltages takes place, does the principle of covering a

202 particular service voltage stress by a specified withstand voltage apply.

203 The annex contains examples of insulation co-ordination for LCC HVDC converters which

204 support the concepts described in the main text, and the basic analytical techniques used.

205 1.2 Additional background

206 The use of power semi-conductor device in a series and/or parallel arrangement, along with the

207 unique control and protection strategies employed in the conversion process, has ramifications

208 requiring particular consideration of overvoltage protection of equipment in converter stations

209 compared with substations in a.c. systems. This standard outlines the procedures for evaluating

210 the overvoltage stresses on the converter station equipment subjected to combined d.c., a.c.

211 power frequency, harmonic and impulse voltages. The criteria for determining the protective

212 levels of series and/or parallel combinations of surge arresters used to ensure optimal

213 protection are also presented.

214 Concerning surge arrester protection, this standard deals only with metal-oxide surge arresters,

215 without gaps, which are used in modern HVDC converter stations. The basic arrester

216 characteristics, requirements for these arresters and the process of evaluating the maximum

217 overvoltages to which they may be exposed in service, are presented. Typical arrester

218 protection schemes and stresses of arresters are presented, along with methods to be applied

219 for determining these stresses.

220 This standard discusses insulation co-ordination related to line commutated converter (LCC)

221 HVDC converter stations. The insulation coordination of voltage sourced converters (VSC) is

222 not part of this standard.
223 2 Normative references

224 The following documents are referred to in the text in such a way that some or all of their content

225 constitutes requirements of this document. For dated references, only the edition cited applies.

226 For undated references, the latest edition of the referenced document (including any

227 amendments) applies.

228 IEC 60060-1, High-voltage test techniques – Part 1: General definitions and test requirements

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229 IEC 60071-1:2019, Insulation co-ordination – Part 1: Definitions, principles and rules

230 IEC 60071-2:2018, Insulation co-ordination – Part 2: Application guide

231 IEC 60099-4:2014, Surge arresters – Part 4: Metal-oxide surge arresters without gaps for a.c.

232 systems

233 IEC 60099-9:2014, Surge arresters – Part 9: Metal-oxide surge arresters without gaps for HVDC

234 converter stations
235 IEC 60633, Terminology for high-voltage direct current (HVDC) transmission

236 IEC TS 60815-1:2008, Selection and dimensioning of high-voltage insulators intended for use

237 in polluted conditions – Part 1: Definitions, information and general principles

238 IEC TS 60815-2:2008, Selection and dimensioning of high-voltage insulators intended for use

239 in polluted conditions – Part 2: Ceramic and glass insulators for a.c. systems

240 IEC TS 60815-3:2008, Selection and dimensioning of high-voltage insulators intended for use

241 in polluted conditions – Part 3: Polymer insulators for a.c. systems
242 3 Terms, definitions, symbols and abbreviations
243 3.1 Terms and definition

244 For the purposes of this document, the terms and definitions given in IEC 60071-11 and the

245 following apply.

246 ISO and IEC maintain terminological databases for use in standardization at the following

247 addresses:
248 • IEC Electropedia: available at http://www.electropedia.org/
249 • ISO Online browsing platform: available at http://www.iso.org/obp
250 3.1.1
251 crest value of continuous operating voltage
252 CCOV

253 highest continuously occurring crest value of the voltage at the equipment on the d.c. side of

254 the converter station excluding commutation overshoots
255 3.1.2
256 peak value of continuous operating voltage
257 PCOV

258 highest continuously occurring crest value of the voltage at the equipment on the d.c. side of

259 the converter station including commutation overshoots and commutation notches

260 3.1.3
261 thyristor valve protective firing

262 method of protecting the individual thyristors from excessive forward voltage stresses across

263 individual thyristors, by firing them
264 3.2 Symbols and abbreviation
265 3.2.1 General

266 The list covers only the most frequently used symbols and abbreviations, some of which are

267 illustrated graphically in the single-line diagram of Figure 1 and Figure 2. For a more complete

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268 list of symbols which has been adopted for LCC HVDC converter stations, and also for insulation

269 co- ordination, refer to the standards listed in the normative references (Clause 2) and to the

270 Bibliography.
271 3.2.2 Subscripts
...