IEC TS 63042-202:2021

IEC TS 63042-202 ®
Edition 1.0 2021-10
TECHNICAL
SPECIFICATION
colour
inside
UHV AC transmission systems –
Part 202: UHV AC Transmission line design
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IEC TS 63042-202 ®
Edition 1.0 2021-10
TECHNICAL
SPECIFICATION
colour
inside
UHV AC transmission systems –
Part 202: UHV AC Transmission line design

INTERNATIONAL
ELECTROTECHNICAL
COMMISSION
ICS 29.240.20 ISBN 978-2-8322-1035-7

– 2 – IEC TS 63042-202:2021 © IEC 2021
CONTENTS
FOREWORD . 10
1 Scope . 12
2 Normative references . 12
3 Terms and definitions . 13
4 Symbols and abbreviations . 13
5 UHV AC transmission line requirements . 14
5.1 General requirements . 14
5.2 Reliability requirements. 14
5.3 Electrical requirements . 14
5.4 Security requirements . 14
5.5 Safety requirements . 14
5.6 Environmental impact. 14
5.7 Economy . 14
6 Selection of clearance . 15
6.1 General . 15
6.2 Air gap, tower clearances (strike distance) . 15
6.2.1 Power frequency voltage . 15
6.2.2 Switching overvoltage . 15
6.2.3 Lightning overvoltage . 15
6.3 Phase to phase spacing (Horizontal, Vertical) . 16
6.4 Ground clearances – Statutory requirements, electric and magnetic field
limits . 16
6.5 Conductor-earth wire spacing, shielding angle – Lightning performance
criteria . 16
7 Insulation coordination, insulator and insulator string design . 17
7.1 General . 17
7.2 Insulation requirements – electrical design considerations . 17
7.3 Insulating materials, type of insulators . 17
7.4 Insulator string configurations for disc type insulators . 18
7.5 Mechanical design criteria of insulator strings and associated hardware
fittings . 19
8 Bundle-conductor selection . 19
8.1 General . 19
8.2 Conductor types . 19
8.3 Bundle conductor configurations . 20
8.3.1 Number of sub-conductors . 20
8.3.2 Bundle spacing . 20
8.4 Conductor bundle selection process . 20
8.4.1 Cross-section of conductor . 20
8.4.2 Conductor ampacity . 20
8.4.3 Requirements for electromagnetic environment . 21
8.4.4 Capital cost and loss evaluation . 21
8.5 Mechanical strength . 21
8.6 Conductor accessories . 22
8.6.1 General requirements for fittings . 22
8.6.2 Type and design features of link fittings, vibration dampers, spacers . 22
9 Earth wire/OPGW selection . 23

9.1 General . 23
9.2 Type of earth wire/OPGW . 23
9.3 Design Criteria/Requirements Specific to UHV Lines. 23
9.4 Induced voltages on earth wire . 23
10 Tower and foundation design . 24
10.1 General . 24
10.2 Tower classification . 24
10.2.1 General . 24
10.2.2 Conductor configuration . 24
10.2.3 Constructional features . 29
10.2.4 Line deviation angle . 29
10.2.5 Tower extensions . 30
10.2.6 Specific requirements . 30
10.3 Tower design . 30
10.3.1 General . 30
10.3.2 Selection of tower geometry based on electrical clearances . 30
10.3.3 Calculation of loads on tower . 31
10.3.4 Analysis using software . 31
10.3.5 Full scale tower testing . 32
10.3.6 Tower design methodology . 32
10.4 Foundation design . 33
10.4.1 General . 33
10.4.2 Open cast type foundations . 34
10.4.3 Raft type foundations . 34
10.4.4 Deep foundations (Pile/Well/Pier/Steel Anchor type) . 35
11 Environmental considerations . 35
11.1 General . 35
11.2 Electric field . 35
11.2.1 General . 35
11.2.2 Reference level of electric field . 35
11.2.3 Prediction of electric field . 36
11.2.4 Mitigation measures of electric field . 36
11.3 Magnetic field . 36
11.3.1 General . 36
11.3.2 Reference level of magnetic field . 36
11.3.3 Prediction of magnetic field . 36
11.3.4 Mitigation measures of magnetic field . 37
11.4 Corona noise (audible noise with corona discharge) . 37
11.4.1 General . 37
11.4.2 Characteristics of corona noise . 37
11.4.3 Reference level of corona noise . 37
11.4.4 Prediction of corona noise . 38
11.4.5 Mitigation measures of corona noise . 38
11.5 Radio interference with corona discharge . 38
11.5.1 General . 38
11.5.2 Characteristics of radio interference . 38
11.5.3 Reference level of radio interference . 39
11.5.4 Prediction of radio interference . 39
11.5.5 Mitigation measures of radio interference . 39

– 4 – IEC TS 63042-202:2021 © IEC 2021
11.6 Wind noise . 39
Annex A (informative) Experimental results and considerations on environmental
performance of UHV AC transmission lines in different countries . 40
A.1 General . 40
A.2 Experimental results and considerations on environmental performance of
UHV AC transmission lines in China . 40
A.2.1 Radio interference . 40
A.2.2 Audible noise . 40
A.2.3 Electric field . 41
A.3 Experimental results and considerations on environmental performance of
UHV AC transmission lines in India . 41
A.3.1 Electrical Clearances from buildings, structures, etc. . 41
A.3.2 Electric field . 41
A.3.3 Radio interference . 41
A.3.4 Audible noise . 41
A.4 Experimental results and considerations on environmental performance of
UHV AC transmission lines in Japan . 42
A.4.1 General . 42
A.4.2 AN (audible noise) . 42
A.4.3 RI (Radio Interference) . 43
A.4.4 EMF (Electromagnetic field) . 43
A.4.5 Electromagnetic induction interference, Electrostatic induction
interference . 45
A.4.6 Wind noise from conductor . 45
A.4.7 Ice and snow falling from conductor . 46
A.4.8 Landscape impact . 47
A.4.9 Nature conservation. 48
Annex B (informative) Design practice of UHV AC transmission lines in different
countries . 50
B.1 General . 50
B.2 Design practice in China . 50
B.2.1 General . 50
B.2.2 Conductor and earth wire . 50
B.2.3 Electrical clearances . 52
B.2.4 Insulation coordination . 53
B.2.5 Tower and foundation . 56
B.3 Design practice in India. 58
B.3.1 General . 58
B.3.2 Challenges in development and solutions . 58
B.3.3 Conductor selection . 58
B.3.4 Electrical clearances . 60
B.3.5 Insulation requirements . 61
B.3.6 1 200 kV test line . 62
B.3.7 400 kV double circuit (upgradable to 1 200 kV single circuit) line . 63
B.4 Design practice in Japan . 65
B.4.1 General . 65
B.4.2 Conductor and earth wire . 66
B.4.3 Insulation coordination . 67
B.4.4 Wind noise . 70
B.4.5 Tower and foundation . 71

Annex C (informative) Construction practice of UHV AC transmission lines in different
countries . 74
C.1 General . 74
C.2 Construction practice in China . 74
C.3 Construction practice in India . 75
C.4 Construction practice in Japan . 75
Annex D (informative) Flashover voltage test result for air clearances in different
countries . 77
D.1 General . 77
D.2 Flashover voltage test result for air clearances in China . 77
D.2.1 50 % Power frequency flashover voltage test results for air clearances
of transmission line structures . 77
D.2.2 50 % Switching impulse flashover voltage test results for air clearances

of transmission line structures . 80
D.2.3 50 % Lightning impulse flashover voltage test results for air clearances
of transmission line structures . 89
D.2.4 Effects of switching overvoltage time to peak on flashover voltage . 92
D.2.5 Tower width correction approaches for air clearances of transmission
line structures . 93
D.3 Flashover voltage test result for air clearances in India . 95
D.4 Flashover voltage test result for air clearances in Japan . 95
D.4.1 50 % Power frequency flashover voltage test results of transmission line
structures . 95
D.4.2 50 % Switching impulse flashover voltage test results for air clearances
of transmission line structures . 96
D.4.3 50 % lightning impulse flashover voltage test results for air clearances
of transmission line structures . 100
Annex E (informative) Restrictions on electromagnetic environment of UHV AC
transmission lines in different countries . 102
E.1 General . 102
E.2 Restrictions in China . 102
E.3 Restrictions in India . 102
E.4 Restrictions in Japan . 103
E.4.1 General . 103
E.4.2 RI (Radio Interference) . 103
E.4.3 AN (Audible Noise) . 103
E.4.4 Electric field . 103
E.4.5 Magnetic field . 104
E.4.6 Communication failure due to electromagnetic induction or electrostatic
induction . 104
E.4.7 Overvoltage due to electromagnetic induction . 104
Annex F (informative) Anti-vibration measures for conductors and earth wires in
different countries . 105
F.1 General . 105
F.2 Anti-vibration measures in China . 105
F.3 Anti-vibration measures in India . 106
F.4 Anti-vibration measures in Japan . 106
F.4.1 Conductor . 106
F.4.2 Earth wire . 106
Annex G (informative) Earth wire regulations in different countries . 108
G.1 General . 108

– 6 – IEC TS 63042-202:2021 © IEC 2021
G.2 Earth wires regulations in China . 108
G.3 Earth wires regulations in India . 108
G.4 Earth wires regulations in Japan . 108
Bibliography . 110

Figure 1 – Typical single circuit vertical configuration tower . 25
Figure 2 – Typical double circuit vertical configuration tower . 25
Figure 3 – Typical single circuit horizontal configuration tower . 26
Figure 4 – Typical single circuit delta configuration tower . 26
Figure 5 – Typical single circuit H-type tower . 27
Figure 6 – Typical double circuit danube configuration tower . 27
Figure 7 – 1 200 kV single circuit vertical configuration tower . 28
Figure 8 – 1 200 kV single circuit horizontal configuration tower . 28
Figure 9 – 1 200 kV double circuit vertical Configuration tower . 28
Figure 10 – 1 200 kV single circuit H-type tower (for gantry) . 29
Figure 11 – Tower design methodology . 33
Figure A.1 – Results of sensing tests under transmission lines . 44
Figure A.2 – Symbols related to wind noise prediction formula . 46
Figure B.1 – Composite insulator profiles . 53
Figure B.2 – 1 200 kV insulator profile . 55
Figure B.3 – 1 200 kV air-gap experimental tests . 60
Figure B.4 – 1 200 kV single circuit test line . 62
Figure B.5 – 1 200 kV double circuit test line . 63
Figure B.6 – 1 200 kV upgradable line –Suspension tower . 64
Figure B.7 – 1 200 kV upgradable line –Tension tower . 64
Figure B.8 – 1 200 kV Tower Prototype Testing . 65
Figure B.9 – UHV AC transmission lines in Japan . 66
Figure B.10 – Shape of conductor . 67
Figure B.11 – Shape of OPGW . 67
Figure B.12 – Foundation type . 73
Figure C.1 – Machinery for foundation construction . 74
Figure D.1 – The arrangement of power frequency flashover voltage test for side-
phase air clearances of 1 000 kV cat-head type towers . 77
Figure D.2 – The 50 % power frequency flashover voltage characteristic for air
clearance from side-phase conductor to tower body for 1 000 kV cat-head type towers. 77
Figure D.3 – The arrangement of power frequency flashover voltage test for side-
phase air clearances of 1 000 kV cup type towers . 78
Figure D.4 – The 50 % power frequency flashover voltage characteristic for air
clearance from side-phase conductor to tower body for 1 000 kV cup type towers 1 000

kV cup type towers . 78
Figure D.5 – The arrangement of power frequency flashover voltage test for air
clearances of 1 000 kV double-circuit lines . 79
Figure D.6 – The 50 % power frequency flashover voltage characteristic for air
clearance from middle-phase conductor with I-type string to tower body for 1 000 kV
double-circuit lines . 79

Figure D.7 – The arrangement of the power frequency flashover voltage test for air
clearances of bottom-phase with I-type string of 1 000 kV double-circuit lines. 80
Figure D.8 – The power frequency flashover voltage characteristic of air clearance
from bottom-phase conductor (with I-type string) to tower body of 1 000 kV double-
circuit lines . 80
Figure D.9 – The arrangement of switching impulse flashover voltage test for side-
phase air clearances of 1 000 kV cat-head type towers . 81
Figure D.10 – The 50 % switching impulse flashover voltage characteristic for air
clearances from conductor to tower body of 1 000 kV lines (with a time to peak of 250
µs) . 81
Figure D.11 – The arrangement of switching impulse flashover voltage test for middle-
phase air clearances of 1 000 kV cat-head type towers . 82
Figure D.12 – The arrangement of switching impulse flashover voltage test for side-

phase air clearances of 1 000 kV cup type towers . 82
Figure D.13 – The 50 % switching impulse flashover voltage characteristic for air
clearances from conductor to tower body of 1 000 kV lines (with a time to peak of
250 µs) . 83
Figure D.14 – The arrangement of switching impulse flashover voltage test for middle-
phase air clearances of 1 000 kV cup type towers . 83
Figure D.15 – The arrangement of switching impulse flashover voltage test at long
time to peak for middle-phase air clearances (with I-type string) of 1 000 kV double-
circuit lines . 84
Figure D.16 – The 50 % switching impulse (1 000 μs) flashover voltage characteristic
for air clearances from conductor to bottom crossarm of 1 000 kV double-circuit lines
(a distance of 9,0 m between conductor and middle crossarm) . 84
Figure D.17 – The arrangement of switching impulse flashover voltage test for air
clearances from middle-phase conductor (with V-type string) to bottom crossarm of

1 000 kV double-circuit lines . 85
Figure D.18 – The 50 % switching impulse (1 000 μs) flashover voltage characteristic
of air clearances from conductor to bottom crossarm of 1 000 kV double-circuit lines . 85
Figure D.19 – The arrangement of switching impulse flashover test for air clearances
from middle-phase conductor (with V-type string) to tower body of 1 000 kV double-
circuit lines . 86
Figure D.20 – The 50 % switching impulse (1 000 μs) flashover voltage characteristic
for air clearances from conductor to tower body of 1 000 kV double-circuit lines . 86
Figure D.21 – The arrangement of switching impulse flashover voltage test for air
clearances from middle-phase conductor (with V-type string) to middle crossarm of

1 000 kV double-circuit lines . 87
Figure D.22 – The 50 % switching impulse (1 000 μs) flashover voltage characteristic
for air clearances from conductor to middle crossarm of 1 000 kV double-circuit lines . 87
Figure D.23 – The arrangement of switching impulse flashover voltage test for air
clearances from bottom-phase conductor (with V-type string) to crossarm of 1 000 kV
double-circuit lines . 88
Figure D.24 – The 50 % switching impulse (1 000 μs) flashover voltage characteristic
for air clearances from conductor to crossarm of 1 000 kV double-circuit lines . 88
Figure D.25 – The arrangement of switching impulse flashover voltage test for air
clearances from bottom-phase conductor (with V-type string) to tower body of 1 000 kV

double-circuit lines . 89
Figure D.26 – The 50 % switching impulse (1 000 μs) flashover voltage characteristic
for air clearances from conductor to tower body of 1 000 kV double-circuit lines . 89
Figure D.27 – The 50 % lightning impulse flashover voltage characteristic for air
clearances from side-phase conductor to tower body of 1 000 kV single-circuit lines . 90

– 8 – IEC TS 63042-202:2021 © IEC 2021
Figure D.28 – The arrangement of lightning impulse flashover voltage test for air
clearances from middle-phase conductor (with I-type string) to bottom crossarm of
1 000 kV double-circuit lines . 90
Figure D.29 – The 50 % lightning impulse flashover voltage characteristic for air
clearances from conductor to lower crossarm of 1 000 kV double-circuit lines . 91
Figure D.30 – The arrangement of lightning impulse flashover voltage test for air
clearances from middle-phase conductor (with V-type string) to bottom crossarm of

1 000 kV double-circuit lines . 91
Figure D.31 – The 50 % positive and negative lightning impulse flashover voltage
characteristic for air clearances from conductor to lower crossarm of 1 000 kV double-
circuit lines . 92
Figure D.32 – Curve of the 50 % switching impulse flashover voltage as a function of
the time to peak for the air clearance from conductor to tower leg of 5 m . 92
Figure D.33 – Tower-width voltage correction factor . 94
Figure D.34 – Tower-width spacing correction factor . 94
Figure D.35 – Effects of tower leg width on switching impulse flashover voltage (with a
time to peak of 720 μs) . 95
Figure D.36 – The 50 % power frequency flashover voltage characteristic for air
clearance for 1 000 kV . 96
Figure D.37 – The arrangement of switching impulse flashover voltage test for air
clearances of 1 000 kV tension type towers . 97
Figure D.38 – The 50 % switching impulse flashover voltage characteristic for air
clearances of 1 000 kV tension type towers . 98
Figure D.39 – The arrangement of switching impulse flashover voltage test for air
clearances of 1 000 kV suspension I type towers . 98
Figure D.40 – The 50 % switching impulse flashover voltage characteristic for air
clearances from conductor to tower body of 1 000 kV suspension I type towers . 99
Figure D.41 – The arrangement of switching impulse flashover voltage test for air
clearances of 1 000 kV suspension V type towers . 99
Figure D.42 – The 50 % switching impulse flashover voltage characteristic for air
clearances of 1 000 kV suspension V type towers . 100
Figure D.43 – The 50 % Lightning impulse flashover voltage characteristic for air
clearance for 1 000 kV . 101
Figure F.1 – Resonance frequency type vibration damper . 105
Figure F.2 – Shape of distributed damper . 107

Table A.1 – Design limits for radio interference in China . 40
Table A.2 – Criteria for environmental noises in the five categories of areas in cities
(dB (A)) . 40
Table A.3 – Reference level of electric field and ground height of conductor . 44
Table B.1 – Conductor type selection . 50
Table B.2 – Conductor characteristics . 51
Table B.3 – Coefficient k . 52
i
Table B.4 – Recommended configuration of tension insulator string in light and medium
ice zone . 54
Table B.5 – Recommended configuration of tension insulator string in substation outlet
span . 54
Table B.6 – Recommended value of single circuit line air gap . 55
Table B.7 – Recommended value of double circuit line air gap . 55

Table B.8 – Conductor capacity . 59
Table B.9 – Conductor surface gradient . 59
Table B.10 – Conductor radio interference . 59
Table B.11 – Conductor audible noise . 59
Table B.12 – Conductor electric field . 60
Table B.13 – Salient results of the experimental tests . 61
Table B.14 – Salient features of the 1 200 kV test lines . 63
Table B.15 – Salient features of 1 200 kV upgraded transmission line . 65
Table B.16 – UHV AC transmission lines in Japan . 66
Table B.17 – Conductor configuration and AN . 66
Table B.18 – Specifications of insulator . 68
Table B.19 – Withstand voltage of single insulator in pollution [kV/unit] . 68
Table B.20 – Withstand voltage of single insulator under snow [kV/unit] . 68
Table B.21 – Altitude correction factor K . 69
Table B.22 – Loads for tower design . 72
Table D.1 – Switching impulse flashover voltages of side-phase air clearances of 1 000
kV cat-head type towers with different test time to peak . 81
Table D.2 – The switching impulse flashover voltage of air clearances from middle-
phase conductor to tower for 1 000 kV full-scale towers . 82
Table D.3 – The switching impulse flashover voltage for air clearance from the middle-
phase conductor to tower window in the arrangement shown in Figure D.14 a) and
Figure D.14 b) . 83
Table D.4 – Altitude correction factor K . 96
Table D.5 – Gap coefficient k . 96
Table D.6 – Altitude correction factor K . 97
Table D.7 – Gap coefficient k . 100
Table E.1 – Radio interference.
...