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BS EN 60071-5:2015

$215.11

Insulation co-ordination – Procedures for high-voltage direct current (HVDC) converter stations

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BSI 2015 100
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This part of IEC 60071 provides guidance on the procedures for insulation co-ordination of high-voltage direct current (HVDC) converter stations, without prescribing standardized insulation levels.

This standard applies only for HVDC applications in high-voltage a.c. power systems and not for industrial conversion equipment. Principles and guidance given are for insulation coordination purposes only. The requirements for human safety are not covered by this standard.

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PDF Pages PDF Title
6 English
CONTENTS
10 INTRODUCTION
11 1 General
1.1 Scope
1.2 Additional background
12 2 Normative references
3 Terms and definitions
13 Tables
Table 1 – Classes and shapes of overvoltages, standard voltage shapes and standard withstand voltage tests
18 4 Symbols and abbreviations
4.1 General
4.2 Subscripts
4.3 Letter symbols
19 4.4 Abbreviations
5 Typical HVDC converter station schemes
21 Figures
Figure 1 – Possible arrester locations in a pole with two 12-pulse converters in series
22 Figure 2 – Possible arrester locations for a back-to-back converter station
Table 2 – Symbol description
23 6 Principles of insulation co-ordination
6.1 General
6.2 Essential differences between a.c. and d.c. systems
6.3 Insulation co-ordination procedure
24 6.4 Comparison of withstand voltage selection in a.c. and d.c. systems
25 Table 3 – Comparison of the selection of withstand voltages for a.c. equipment with that for HVDC converter station equipment
26 7 Voltages and overvoltages in service
7.1 Continuous operating voltages at various locations in the converter station
27 Figure 3 – HVDC converter station with one 12-pulse converter bridge per pole
29 Figure 4 – Continuous operating voltages at various locations (location identification according to Figure 3)
30 7.2 Peak continuous operating voltage (PCOV) and crest continuous operating voltage (CCOV)
31 Figure 5 – Operating voltage of a valve arrester (V), rectifier operation
Figure 6 – Operating voltage of a mid-point arrester (M), rectifier operation
32 7.3 Sources and types of overvoltages
Figure 7 – Operating voltage of a converter bus arrester (CB), rectifier operation
33 7.4 Temporary overvoltages
7.4.1 General
7.4.2 Temporary overvoltages on the a.c. side
7.4.3 Temporary overvoltages on the d.c. side
7.5 Slow-front overvoltages
7.5.1 General
7.5.2 Slow-front overvoltages on the a.c. side
34 7.5.3 Slow-front overvoltages on the d.c. side
35 7.6 Fast-front, very-fast-front and steep-front overvoltages
36 8 Arrester characteristics and stresses
8.1 Arrester characteristics
37 8.2 Arrester specification
8.3 Arrester stresses
8.3.1 General
38 8.3.2 AC bus arrester (A)
39 8.3.3 AC filter arrester (FA)
8.3.4 Transformer valve winding arresters (T)
8.3.5 Valve arrester (V)
42 8.3.6 Bridge arrester (B)
43 8.3.7 Converter unit arrester (C)
8.3.8 Mid-point d.c. bus arrester (M)
44 8.3.9 Converter unit d.c. bus arrester (CB)
8.3.10 DC bus and d.c. line/cable arrester (DB and DL/DC)
8.3.11 Neutral bus arrester (E, EL, EM in Figure 3, EB, E1, EL, EM in Figure 1)
45 8.3.12 DC reactor arrester (DR)
46 8.3.13 DC filter arrester (FD)
8.3.14 Earth electrode station arrester
8.4 Protection strategy
8.4.1 General
8.4.2 Insulation directly protected by a single arrester
47 8.4.3 Insulation protected by more than one arrester in series
8.4.4 Valve side neutral point of transformers
8.4.5 Insulation between phase conductors of the converter transformer
8.4.6 Summary of protection strategy
48 Table 4 – Arrester protection on the d.c. side: Single 12-pulse converter (Figure 3)
Table 5 – Arrester protection on the d.c. side: Two 12-pulse converters (Figure 1)
49 8.5 Summary of events and stresses
50 Table 6 – Events stressing arresters: Single 12-pulse converter (Figure 3)
Table 7 – Types of arrester stresses for different events: Single 12-pulse converter (Figure 3)
51 9 Design procedure of insulation co-ordination
9.1 General
9.2 Arrester requirements
52 Table 8 – Arrester requirements
53 9.3 Characteristics of insulation
9.4 Representative overvoltages (Urp)
Table 9 – Representative overvoltages and required withstand voltages
54 9.5 Determination of the co-ordination withstand voltages (Ucw)
9.6 Determination of the required withstand voltages (Urw)
56 9.7 Determination of the specified withstand voltage (Uw)
10 Study tools and system modelling
10.1 General
10.2 Study approach and tools
Table 10 – Indicative values of ratios of required impulse withstandvoltage to impulse protective level
57 10.3 System details
10.3.1 Modelling and system representation
58 Table 11 – Origin of overvoltages and associated frequency ranges
59 10.3.2 AC network and a.c. side of the HVDC converter station
Figure 8 – One pole of an HVDC converter station
60 10.3.3 DC overhead line/cable and earth electrode line details
10.3.4 DC side of an HVDC converter station details
61 11 Creepage distances
11.1 General
11.2 Base voltage for creepage distance
11.3 Creepage distance for outdoor insulation under d.c. voltage
62 11.4 Creepage distance for indoor insulation under d.c. or mixed voltage
11.5 Creepage distance of a.c. insulators
12 Clearances in air
64 Annex A (informative) Example of insulation co-ordination for conventional HVDC converters
A.1 General
A.2 Arrester protective scheme
A.3 Arrester stresses, protection and insulation levels
A.3.1 General
65 A.3.2 Slow-front overvoltages transferred from the a.c. side
A.3.3 Earth fault between valve and upper bridge transformer bushing
68 A.4 Transformer valve side withstand voltages
A.4.1 Phase-to-phase
69 A.4.2 Upper bridge transformer phase-to-earth (star)
A.4.3 Lower bridge transformer phase-to-earth (delta)
A.5 Air-insulated smoothing reactors withstand voltages
A.5.1 Terminal-to-terminal slow-front overvoltages
70 A.5.2 Terminal-to-earth
A.6 Results
71 Figure A.1 – AC and d.c. arresters
Figure A.2 – Valve arrester stressesfor slow-front overvoltages from a.c. side
72 Figure A.3 – Arrester V2 stress for slow-front overvoltagefrom a.c. side
Figure A.4 – Valve arrester stresses for earth fault between valveand upper bridge transformer bushing
73 Figure A.5 – Arrester V1 stress for earth fault between valveand upper bridge transformer bushing
74 Annex B (informative) Example of insulation co-ordination for capacitor commutated converters (CCC) and controlled series capacitor converters (CSCC)
B.1 General
B.2 Arrester protective scheme
B.3 Arrester stresses, protection and insulation levels
B.3.1 General
75 B.3.2 Transferred slow-front overvoltages from the a.c. side
76 B.3.3 Earth fault between valve and upper bridge transformer bushing
79 B.4 Transformer valve side withstand voltages
B.4.1 Phase-to-phase
B.4.2 Upper bridge transformer phase-to-earth (star)
B.4.3 Lower bridge transformer phase-to-earth (delta)
80 B.5 Air-insulated smoothing reactors withstand voltages
B.5.1 Slow-front terminal-to-terminal overvoltages
B.5.2 Terminal-to-earth
81 B.6 Results
82 Figure B.1 – AC and d.c. arresters for CCC and CSCC converters
83 Figure B.2 – Valve arrester stresses for slow-front overvoltages from a.c. side
84 Figure B.3 – Arrester V2 stress for slow-front overvoltage from a.c. side
86 Figure B.4 – Valve arrester stresses for earth fault between valveand upper bridge transformer bushing
87 Figure B.5 – Arrester V1 stress for earth fault between valveand upper bridge transformer bushing
88 Figure B.6 – Stresses on capacitor arresters Ccc and Csc during earth fault between valve and upper bridge transformer bushing
89 Annex C (informative) Considerations for insulation co-ordination of some special converter configurations
C.1 Procedure for insulation co-ordination of back-to-back type of HVDC links
C.2 Procedure for insulation co-ordination of parallel valve groups
C.2.1 General
90 C.2.2 AC bus arrester (A)
C.2.3 AC filter arrester (FA)
C.2.4 Valve arrester (V)
C.2.5 Bridge arrester (B) and converter unit arrester (C)
C.2.6 Mid-point arrester (M)
C.2.7 Converter unit d.c. bus arrester (CB)
Figure C.1 – Expanded HVDC converter with parallel valve groups
91 C.2.8 DC bus and d.c. line/cable arrester (DB and DL)
C.2.9 Neutral bus arrester (E)
C.2.10 DC reactor arrester (DR)
C.2.11 DC filter arrester (FD)
C.2.12 New converter stations with parallel valve groups
C.3 Procedure for insulation co-ordination of upgrading existing systems with series-connected valve groups
C.3.1 General
92 C.3.2 AC bus arrester (A)
C.3.3 AC filter arrester (FA)
C.3.4 Valve arrester (V)
C.3.5 Bridge arrester (B) and converter unit arrester (C)
C.3.6 Mid-point arrester (M)
Figure C.2 – Upgraded HVDC converter with series valve group
93 C.3.7 Converter unit d.c. bus arrester (CB), d.c. bus and d.c. line/cable arrester (DB and DL)
C.3.8 Neutral bus arrester (E)
C.3.9 DC reactor arrester (DR)
C.3.10 DC filter arrester (FD)
C.4 Overvoltages in the a.c. network due to closely coupled HVDC links
94 C.5 Effect of gas-insulated switchgear on insulation co-ordination of HVDC converter stations
95 Annex D (informative) Typical arrester characteristics
Figure D.1 – Typical arrester V-I characteristics
96 Bibliography
BS EN 60071-5:2015
$215.11