UHV AC transmission systems - Part 102: General system design

This part of IEC 63042-102 specifies the procedure to plan and design UHV transmission project and the items to be considered.

Prenosni sistemi UHV AC - Načrtovanje splošnih zahtev

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SLOVENSKI STANDARD
oSIST prEN IEC 63042-102:2020
01-december-2020
Prenosni sistemi UHV AC - Načrtovanje splošnih zahtev
UHV AC transmission systems - General system design
Ta slovenski standard je istoveten z: prEN IEC 63042-102:2020
ICS:
29.240.01 Omrežja za prenos in Power transmission and
distribucijo električne energije distribution networks in
na splošno general
oSIST prEN IEC 63042-102:2020 en

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

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oSIST prEN IEC 63042-102:2020
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oSIST prEN IEC 63042-102:2020
122/94/CDV
COMMITTEE DRAFT FOR VOTE (CDV)
PROJECT NUMBER:
IEC 63042-102 ED1
DATE OF CIRCULATION: CLOSING DATE FOR VOTING:
2020-09-25 2020-12-18
SUPERSEDES DOCUMENTS:
122/92/CD, 122/93/CC
IEC TC 122 : UHV AC TRANSMISSION SYSTEMS
SECRETARIAT: SECRETARY:
Japan Mr Eiichi Zaima
OF INTEREST TO THE FOLLOWING COMMITTEES: PROPOSED HORIZONTAL STANDARD:
TC 8,TC 14,SC 17A,SC 17C,TC 37,TC 99
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:
UHV AC transmission systems – General system design
PROPOSED STABILITY DATE: 2024
NOTE FROM TC/SC OFFICERS:

Copyright © 2020 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 63042-102:2020
63042-102/Ed1/CDV  IEC (E) – 2 – 122/94/CDV
1 CONTENTS

2 FOREWORD ........................................................................................................................... 3

3 INTRODUCTION ..................................................................................................................... 5

4 1 Scope .............................................................................................................................. 6

5 2 Normative references ...................................................................................................... 6

6 3 Terms and definitions ...................................................................................................... 6

7 4 Objective and key issues of UHV AC transmission application ......................................... 6

8 4.1 Objective ................................................................................................................ 6

9 4.2 Key application issues ............................................................................................ 7

10 5 Required studies on UHV AC system planning / design ................................................... 7

11 5.1 General ................................................................................................................... 7

12 5.2 Required studies ..................................................................................................... 7

13 5.3 Required analyses tools .......................................................................................... 8

14 6 UHV AC system planning................................................................................................. 9

15 6.1 General ................................................................................................................... 9

16 6.2 Scenario planning ................................................................................................. 11

17 6.3 Scenario procedure ............................................................................................... 11

18 6.3.1 Power transmission capacity.......................................................................... 11

19 6.3.2 System voltage .............................................................................................. 12

20 6.3.3 Route selection .............................................................................................. 12

21 6.3.4 Series compensation ..................................................................................... 13

22 6.4 Required parameter .............................................................................................. 13

23 6.5 Transmission network (topology) ........................................................................... 14

24 6.6 Reliability .............................................................................................................. 14

25 7 UHV AC system design ................................................................................................. 15

26 7.1 General ................................................................................................................. 15

27 7.2 Reactive power management ................................................................................ 15

28 7.3 Reclosing schemes ............................................................................................... 15

29 7.4 Zero offset phenomenon ....................................................................................... 17

30 7.5 Protection and control system ............................................................................... 17

31 7.6 Insulation design (cost effectiveness) ................................................................... 18

33 Figure 1 Analysis tool by time domain ..................................................................................... 8

34 Figure 2 The flowchart for reactive power compensation configuration .................................. 10

35 Figure 3 Π equivalent circuit ................................................................................................. 11

36 Figure 4 Four-legged reactor ................................................................................................ 16

37 Figure 5 Fast reclosing using High Speed Earthing Switches (HSES) ................................... 17

38 Figure 6 Procedure for Insulation Design .............................................................................. 19

40 Table 1 Specification to reclosing scheme ............................................................................ 17

41 Annex A (informative) History of development of UHV AC transmission technologies ………. 20

42 Annex B (informative) Experience of UHV AC transmissions (Use case) ………..……………...23

43 Annex C (informative) Summary of system technologies specific to UHV AC transmission

44 systems ………..………..………..………..………..………..………..………..………..………………49
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46 INTERNATIONAL ELECTROTECHNICAL COMMISSION
47 ____________
49 UHV AC TRANSMISSION SYSTEMS –
51 Part 102: General system design
53 FOREWORD

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

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

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

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

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

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

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

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

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

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

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

65 interested IEC National Committees.

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

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

69 misinterpretation by any end user.

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

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

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

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

82 indispensable for the correct application of this publication.

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

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

85 IEC 63042-102 has been prepared by IEC technical committee TC122: UHV AC transmission

86 systems.
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oSIST prEN IEC 63042-102:2020
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88 The text of this International Standard is based on the following documents:
FDIS Report on voting
XX/XX/FDIS XX/XX/RVD

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

91 report on voting indicated in the above table.

92 This document has been drafted in accordance with the ISO/IEC Directives, Part 2.

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

94 stability date indicated on the IEC website under "http://webstore.iec.ch" in the data related to

95 the specific document. At this date, the document will be
96 • reconfirmed,
97 • withdrawn,
98 • replaced by a revised edition, or
99 • amended.
100
101
102
103
104
105
106
107
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108 INTRODUCTION

109 Large-capacity power sources including large-scale renewable energy have recently been

110 developed, which are generally located far away from the load center. To meet the requirements

111 for large power transmission, some countries have introduced, or are considering introducing,

112 ultra high voltage (UHV) transmission systems, overlaying these on the existing transmission

113 systems at lower voltages such as 420 kV and 550 kV.

114 The objective of UHV AC power system planning/design is to achieve both economic efficiency

115 and high reliability, considering its impact on systems at lower voltages such as 420 kV and

116 550 kV.

117 Moreover, UHV AC transmission systems requires comparatively large space so that how to

118 realize to minimize and optimize the size and structure of UHV AC transmission lines and

119 substation apparatus is another important issue.
120
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121 UHV AC TRANSMISSION SYSTEMS –
122
123 Part 102: General system design
124
125
126 1 Scope

127 This part of IEC 63042-102 specifies the procedure to plan and design UHV transmission

128 project and the items to be considered.
129 2 Normative references

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

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

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

133 amendments) applies.
134 IEC 63042-101, Voltage regulation and insulation design
135 3 Terms and definitions

136 For the purposes of this document, the following terms and definitions apply.

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

138 addresses:
139 – IEC Electropedia: available at http://www.electropedia.org/
140 – ISO Online browsing platform: available at http://www.iso.org/obp
141 4 Objective and key issues of UHV AC transmission application
142 4.1 Objective

143 Recently, large-capacity power sources including large-scale renewable energy have been

144 developed, in most cases, far away from the load centres. To fully utilise these facilities, it is

145 important to transmit power generation from these sources efficiently. Evacuation through Extra

146 High Voltage (EHV) network enhancements would need more lines (Right-of-way, ROW) and

147 substation, increasing transmission losses and worsening fault current problems.

148 UHV transmission systems are characterized with large capacity over long distances and can

149 provide a solution to address above issues by minimising ROW and Switchyard requirements,

150 effectively less losses, improvement of fault current conditions etc.

151 For example, the transmission Surge Impedance Loading (SIL) capacity of an 1100 kV

152 transmission line can replace 4 to 5 of 550 kV lines, effectively reducing one-third of the tower

153 materials and one-half of the wires. It can save construction cost of the power lines and

154 substations.
155 UHV transmission system has many features as follows:
156 – Large- capacity, long-distance and high-efficiency power transmission
157 – Decrease of ROW required for transferring per unit GW
158 – Improvement of fault current condition and system stability
159 – Reduction of environmental impact
160 – Reduction of transmission losses
161 Many UHV projects have been launched and are in commercial operation.
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162 Note: Introduction of an UHV AC transmission systems can lessen or solve fault current problems in most cases,

163 however, the effect of UHV on short circuit issues should be seen in totality.

164 4.2 Key application issues

165 UHV AC transmission systems are capable of transmitting large amounts of electric power.

166 However, if a failure occurs in an UHV AC system, the system influence can be severe from the

167 viewpoints of reliability and overall security of the supply of the power system. Especially, UHV

168 AC transmission systems design should be considered to improve lightning and switching

169 protection performance.

170 In UHV AC transmission systems, typical phenomenon depends on the length of the

171 transmission line. For the phenomenon due to the long transmission line, reactive power issues

172 such as voltage rise due to the Ferranti effect and geometrical mean distance for increasing

173 surge impedance loading (SIL) should be taken care. For high voltage issues, secondary arc

174 extinction, TOV (Temporary Over-Voltage) at load shedding, and DC time constant of short-

175 circuit currents are also necessary to be considered.

176 In addition, size and cost of equipment are large so that system design should consider

177 minimizing visual impact, construction/maintenance costs and transmission losses, and

178 increasing the network connectivity by forecasting generation and load scenarios.

179 5 Required studies on UHV AC system planning / design
180 5.1 General

181 Early strategic system planning is conducted to meet their load growth and power source

182 development planning. Once it is determined that a new transmission line is required in the

183 system, preliminary economic feasibility study and project design begin.

184 In the term of project design, three primary decisions must be addressed in a transmission-line

185 project at the conceptual stage at first capacity, voltage, and route.

186 Furthermore, strategic planning, as it relates to the environmental permitting process, is often

187 overlooked or viewed as being of secondary importance. Early strategic planning for the project-

188 specific environmental review process can avoid significant effects on a project’s schedule,

189 costs, and ultimate success.
190 5.2 Required studies

191 The analytical studies can be divided into three types, corresponding to chronological phases

192 of a project’s planning, design, and implementation:
193 1) System planning study

194 In the planning stages, wherever new lines are needed, the voltage and current ratings, and

195 major auxiliary equipment such as shunt compensation are determined. At this stage, system

196 contingencies are considered. Further studies need to be carried out for various power demand

197 and generation scenarios, typical ones including peak demand, off peak demand for various

198 seasons (Summer/Winter/Rain), to check adequacy of the proposed transmission system. The

199 basic study is a power flow calculation for which positive sequence parameters are adequate.

200 2) System impact study or detailed system design study

201 The impact of new planned transmission or generation on the power system should be

202 evaluated by the system impact study. Based on the impact study, the high-level specification

203 has to be determined. The system impact study may result in some adjustments, or mitigations

204 applied to the system.
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205 Study topics include harmonic resonance, short-circuit currents, transient stability, voltage

206 stability, and system relaying. The study tools include short circuit, stability, and harmonic

207 analysis programs, and in some cases an electromagnetic transient analytical program to

208 explore resonant overvoltages. The modelling needs to vary from lumped parameter to

209 distributed parameter, from positive sequence to three-phase unbalanced representation, and

210 from DC to a few kHz, depending on the subject. Models are often generic in early studies, later

211 progressing to specific models for particular equipment.
212 3) Equipment and system design study

213 Detailed protection and operating procedures for the switchgear, shunt compensation, and

214 related equipment are established. The basic study tool is an electromagnetic transient

215 analytical program.

216 Accurate frequency dependent models are preferable and sometimes necessary for many of

217 these studies.
218 5.3 Required analyses tools

219 The main considerations are power flow, fault current, voltage control, dynamic stability and

220 operational criteria that include reliability and system security.

221 Once the high-level specification (number and type of conductors, voltage level, current rating,

222 and reactive power compensation) has been determined, a more detailed design phase follows

223 to specify equipment, such as circuit breakers, shunt reactors, and surge arrestors. No

224 foreseeable problem should affect the reliable and safe operation of the system.

225 The analysis tool by time-domain mentioned in Figure 1.
226
227 Figure 1 Analysis tool by time domain

228 Line Constants – a program that calculates and represents electrical RLC parameters in a

229 matrix form for a general system of tower and conductors, over a range of frequencies, and

230 using either transposed or full unbalanced assumptions. This function may be bundled with

231 another tool, or used separately.
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232 Power flow – calculate steady-state voltages and currents based on a positive sequence model,

233 with nonlinear loads. The line model is symmetric and transposed. Power flow is the basic tool

234 for transmission planning.

235 Short-Circuit – a program that solves for voltage and current during faults, especially three-

236 phase and single-phase-to-ground faults. The model is linear, symmetric, and assumes phase

237 transposition. An auxiliary protection function simulates the response of relays to fault current

238 and voltage.

239 Dynamics – a time-domain simulator based on numerical integration of differential equations. It

240 differs from an Electromagnetic Transients Program (EMTP) in focusing on (slower)

241 electromechanical and control system transients, rather than electromagnetic transients. The

242 models are sometimes linear and balanced. The program usually includes eigenvalue analysis,

243 or other functions for small-signal stability.

244 Harmonics – a frequency domain program that solves voltage and current over a range of

245 frequencies, using linear or non-linear load and source models, and balanced or unbalanced

246 impedances. The frequency-scan function outputs driving point impedance, as obtained from

247 the bus voltage for a unit current injection.

248 EMTP – a time-domain or transient simulator based on numerical integration of differential

249 equations, including non-linear component models, unbalanced impedances, and frequency-

250 dependent RLC parameters. An EMTP can also perform frequency scans, and may include an

251 AUX program of EMTP Cable Constants.

252 Electromagnetic Field Program – A program can compute electric and magnetic fields in the air

253 and soil, as well as electric potentials, and the current distribution in the soil and in the

254 conductors.
255 6 UHV AC system planning
256 6.1 General

257 Generally, the planning study is proceeded by the following steps. As UHV AC system planning

258 has specific requirements, some considerations are necessary in each steps.
259 6.1.1 Transmission capacity considering their routes and line types to use

260 In the planning and design of power grid, increasing the voltage level of the transmission line

261 to UHV not only increases the transmission capacity, but also reduces the cost of the

262 transmission system and increases the corridor utilization rate of the transmission line.

263 The economic transmission distance of UHV transmission lines can reach 1 000~1 500 km or

264 even longer. The single line transmission capacity with 8 bundled wires can reach to 12 000

265 MW. In the selection of UHV transmission capacity, the economic benefits of the entire power

266 grid should be considered, rather than being limited to the economic benefits of a transmission

267 line project.
268 6.1.2 Reactive power management issues

269 In the planning of the power system, the planning of reactive power supply and reactive power

270 compensation facilities must be included. In the engineering design of UHV AC transmission,

271 the design of reactive power supply and reactive power compensation facilities should be

272 carried out.

273 Appropriate amount of reactive power supply should be planned and installed in UHV AC system

274 to meet the system voltage regulation requirements and reduce the unintended reactive power

275 transfer between different network nodes.
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276 Sufficient amount of reactive power supply with flexible adjustable capacity, as well as reserve

277 capacity of reactive power should be maintained.

278 The configuration of reactive power compensation and equipment type selection should be

279 technically and economically compared.

280 Planning and design of reactive power compensator for UHV AC system should meet the

281 overvoltage limiting requirement of UHV AC transmission systems.

282 The process of configuring reactive power compensation for UHV AC system is as follows:

283 1) Identify the range of likely active power flow across the UHV line, calculate and analyze the

284 characteristics of reactive power and voltage profiles along the UHV line, taking into account

285 of charging reactive power produced by UHV AC lines and reactive power loss under

286 different power flows. (Step 1)

287 2) Select UHV transformer tap position to avoid overvoltage under a range of operating

288 conditions taking into account UHV substation location, number of transmission lines

289 connected, and system operation mode. (Step 2)

290 3) Select capacity and location of UHV shunt reactor with consideration of limiting temporary

291 overvoltage and reducing secondary arc current, and balancing charging power of lines and

292 flexibly controlling bus voltage. (Step 3)

293 4) Identify total and unit capacity of compensator installed in tertiary side of the transformer.

294 The total capacity should be selected to reduce the reactive power exchange between

295 different voltage levels and maintain bus voltage in an admissible range; the selection of

296 single bank capacity should consider the voltage fluctuation induced by switching of single

297 group capacitor or reactor within a reasonable range. (Step 4)

298 5) Check if the dynamic reactive power reserve provided by generators is adequate within their

299 reactive power capability range. If it is adequate, then the process stops, otherwise go back

300 to Step 4. (Step 5)
301 Figure 2 shows the process of configuring reactive power compensation
302
303 Figure 2 The flowchart for reactive power compensation configuration
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304 6.1.3 Environmental issues

305 The environmental impact of power transmission project, generally includes the impact on the

306 ecological environment, electromagnetic fields, land occupation, visual landscape, and so on.

307 At present, the public's awareness of the quality of the environment in which they live has been

308 strengthened, and more and more attention are paid to the environment impact of power

309 transmission project. Related environment laws and regulations in each country should be

310 complied with.

311 During the UHV AC system planning and feasibility research, environmental issues must be

312 included. UHV AC transmission has advantages in saving the total width of transmission

313 corridor, as a result of its huge transmission capacity. However, because of its higher voltage

314 and rated current, it may cause more serious electromagnetic fields and related problems, which

315 include power frequency electric field, power frequency magnetic field, corona phenomenon,

316 radio interference, audible noise. Corresponding countermeasures should be considered during

317 the substation and transmission line design. Appropriate test and measurement should be

318 carried out to verify the effect of the countermeasure, during research and system

319 commissioning.
320 6.2 Scenario planning

321 System planning mainly include power load forecast, power source development planning and

322 power grid planning. System planning is formulated considering the load growth demand, site

323 selection of power source, and paths and networking how to connect the demand side and the

324 supply side. Then it power grid planning depends on the power development source planning.

325 Construction of power plants requires several years but its prerequisite is that the corridors and

326 required network enhancement is prepared.

327 Generally speaking, construction period of UHV transmission line may be comparatively longer

328 than those of lower voltage level and is required more restrictions for so that it is necessary to

329 determine when and how to introduce UHV AC transmission systems based on the accumulated

330 experiences and findings as well as demand forecast and then for
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