IEC TR 60071-4:2004

TECHNICAL IEC
REPORT TR 60071-4
First edition
2004-06
Insulation co-ordination –
Part 4:
Computational guide to insulation co-ordination
and modelling of electrical networks

Reference number
IEC/TR 60071-4:2004(E)
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TECHNICAL IEC
REPORT TR 60071-4
First edition
2004-06
Insulation co-ordination –
Part 4:
Computational guide to insulation co-ordination
and modelling of electrical networks
 IEC 2004  Copyright - all rights reserved
No part of this publication may be reproduced or utilized in any form or by any means, electronic or
mechanical, including photocopying and microfilm, without permission in writing from the publisher.
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– 2 – TR 60071-4  IEC:2004(E)
CONTENTS
FOREWORD.7

Scope and object .9
2 Normative references.9
3 Terms and definitions .9
4 List of symbols and acronyms .12
5 Types of overvoltages.12
6 Types of studies .13
6.1 Temporary overvoltages (TOV) .14
6.2 Slow-front overvoltages (SFO) .14
6.3 Fast-front overvoltages (FFO).15
6.4 Very-fast-front overvoltages (VFFO).15
7 Representation of network components and numerical considerations .15
7.1 General .15
7.2 Numerical considerations.15
7.3 Representation of overhead lines and underground cables .18
7.4 Representation of network components when computing temporary
overvoltages .19
7.5 Representation of network components when computing slow-front
overvoltages .25
7.6 Representation of network components when computing fast-front transients.30
7.7 Representation of network components when computing very-fast-front
overvoltages .42
8 Temporary overvoltages analysis .44
8.1 General .44
8.2 Fast estimate of temporary overvoltages.45
8.3 Detailed calculation of temporary overvoltages [2], [9] .45
9 Slow-front overvoltages analysis .48
9.1 General .48
9.2 Fast methodology to conduct SFO studies .48
9.3 Method to be employed.49
9.4 Guideline to conduct detailed statistical methods .49
10 Fast-front overvoltages analysis.52
10.1 General .52
10.2 Guideline to apply statistical and semi-statistical methods .53
11 Very-fast-front overvoltage analysis .58
11.1 General .58
11.2 Goal of the studies to be performed .58
11.3 Origin and typology of VFFO .58
11.4 Guideline to perform studies .60
12 Test cases.60
12.1 General .60
12.2 Case 1: TOV on a large transmission system including long lines .60
12.3 Case 2 (SFO) – Energization of a 500 kV line .68
12.4 Case 3 (FFO) – Lightning protection of a 500 kV GIS substation .73
12.5 Case 4 (VFFO) – Simulation of transients in a 765 kV GIS [51] .80

TR 60071-4  IEC:2004(E) – 3 –
Annex A (informative) Representation of overhead lines and underground cables .86
Annex B (informative) Arc modelling: the physics of the circuit-breaker .90
Annex C (informative) Probabilistic methods for computing lightning-related risk of
failure of power system apparatus .93
Annex D (informative) Test case 5 (TOV) – Resonance between a line and a reactor in
a 400/220 kV transmission system .99
Annex E (informative) Test case 6 (SFO) – Evaluation of the risk of failure of a gas-
insulated line due to SFO . 105
Annex F (informative) Test case 7 (FFO) – High-frequency arc extinction when
switching a reactor . 113

Bibliography . 116

Figure 1 – Types of overvoltages (excepted very-fast-front overvoltages).12
Figure 2 – Damping resistor applied to an inductance .17
Figure 3 – Damping resistor applied to a capacitance .17
Figure 4 – Example of assumption for the steady-state calculation of a non-linear
element.17
Figure 5 – AC-voltage equivalent circuit.19
Figure 6 – Dynamic source modelling .20
Figure 7 − Linear network equivalent .21
Figure 8 − Representation of load in [56] .24
Figure 9 – Representation of the synchronous machine .26
Figure 10 – Diagram showing double distribution used for statistical switches .29
Figure 11 – Multi-story transmission tower [16], H = l + l + l + l .31
1 2 3 4
Figure 12 − Example of a corona branch model .33
Figure 13 −Example of volt-time curve.34
Figure 14 – Double ramp shape.38
Figure 15 – CIGRE concave shape.39
Figure 16 – Simplified model of earthing electrode.41
Figure 17 – Example of a one-substation-deep network modelling .51
Figure 18 – Example of a two-substation-deep network modelling.51
Figure 19 − Application of statistical or semi-statistical methods .53
Figure 20 – Application of the electro-geometric model.56
Figure 21 – Limit function for the two random variables considered: the maximum value
of the lightning current and the disruptive voltage .57
Figure 22 – At the GIS-air interface: coupling between enclosure and earth (Z ), between
overhead line and earth (Z ) and between bus conductor and enclosure (Z ) [33] .59
2 1
Figure 23 − Single-line diagram of the test-case system .62
Figure 24 − TOV at CHM7, LVD7 and CHE7 from system transient stability simulation.63
Figure 25 – Generator frequencies at generating centres Nos. 1, 2 and 3 from system
transient stability simulation .64
Figure 26 – Block diagram of dynamic source model [55].65
Figure 27 − TOV at LVD7 – Electromagnetic transient simulation with 588 kV and
612 kV permanent surge arresters.66

– 4 – TR 60071-4  IEC:2004(E)
Figure 28 − TOV at CHM7 – Electromagnetic transient simulation with 588 kV and
612 kV permanent surge arresters.67
Figure 29 − TOV at LVD7 – Electromagnetic transient simulation with 484 kV switched

metal-oxide surge arresters.67
Figure 30 − TOV at CHM7 – Electromagnetic transient simulation with 484 kV switched
metal-oxide surge arresters.67
Figure 31 – Representation of the system.68
Figure 32 – Auxiliary contact and main .70
Figure 33 – An example of cumulative probability function of phase-to-earth
overvoltages and of discharge probability of insulation in a configuration with trapped
charges and insertion resistors.72
Figure 34 – Number of failure for 1 000 operations versus the withstand voltage of the
insulation .72
Figure 35 – Schematic diagram of a 500 kV GIS substation intended for lightning
studies.
...