SIST-TS CLC IEC/TS 63291-1:2025

SLOVENSKI STANDARD
01-november-2025
Sistemi visokonapetostnega enosmernega omrežja in priključene pretvorniške
postaje - Smernice in seznam parametrov za funkcijsko specifikacijo - 1. del:
Smernice
High voltage direct current (HVDC) grid systems and connected converter stations -
Guideline and parameter lists for functional specifications - Part 1: Guideline
Hochspannungsgleichstrom-Netzsysteme und angeschlossene Umrichterstationen -
Leitfaden und Parameterlisten für funktionale Spezifikationen - Teil 1: Leitfaden
Réseaux en courant continu à haute tension (CCHT) et postes de conversion connectés
- Lignes directrices et listes de paramètres pour les spécifications fonctionnelles - Partie
1: Lignes directrices
Ta slovenski standard je istoveten z: CLC IEC/TS 63291-1:2025
ICS:
29.200 Usmerniki. Pretvorniki. Rectifiers. Convertors.
Stabilizirano električno Stabilized power supply
napajanje
29.240.01 Omrežja za prenos in Power transmission and
distribucijo električne energije distribution networks in
na splošno general
2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.

TECHNICAL SPECIFICATION CLC IEC/TS 63291-1

SPÉCIFICATION TECHNIQUE
TECHNISCHE SPEZIFIKATION September 2025
ICS 29.200; 29.240.01 Supersedes CLC/TS 50654-1:2020
English Version
High voltage direct current (HVDC) grid systems and connected
converter stations - Guideline and parameter lists for functional
specifications - Part 1: Guideline
(IEC/TS 63291-1:2023)
Réseaux en courant continu à haute tension (CCHT) et Hochspannungsgleichstrom-Netzsysteme und
postes de conversion connectés - Lignes directrices et angeschlossene Stromrichterstationen - Leitfaden und
listes de paramètres pour les spécifications fonctionnelles - Parameter-Listen für funktionale Spezifikationen - Teil 1:
Partie 1: Lignes directrices Leitfaden
(IEC/TS 63291-1:2023) (IEC/TS 63291-1:2023)
This Technical Specification was approved by CENELEC on 2025-08-26.

CENELEC members are required to announce the existence of this TS in the same way as for an EN and to make the TS available promptly
at national level in an appropriate form. It is permissible to keep conflicting national standards in force.

CENELEC members are the national electrotechnical committees of Austria, Belgium, Bulgaria, Croatia, Cyprus, the Czech Republic,
Denmark, Estonia, Finland, France, Germany, Greece, Hungary, Iceland, Ireland, Italy, Latvia, Lithuania, Luxembourg, Malta, the
Netherlands, Norway, Poland, Portugal, Republic of North Macedonia, Romania, Serbia, Slovakia, Slovenia, Spain, Sweden, Switzerland,
Türkiye and the United Kingdom.

European Committee for Electrotechnical Standardization
Comité Européen de Normalisation Electrotechnique
Europäisches Komitee für Elektrotechnische Normung
CEN-CENELEC Management Centre: Rue de la Science 23, B-1040 Brussels
© 2025 CENELEC All rights of exploitation in any form and by any means reserved worldwide for CENELEC Members.
Ref. No. CLC IEC/TS 63291-1:2025 E

European foreword
This document (CLC IEC/TS 63291-1:2025) consists of the text of document IEC/TS 63291-1:2023,
prepared by IEC/TC 115 "High Voltage Direct Current (HVDC) transmission for DC voltages above
100 kV".
Attention is drawn to the possibility that some of the elements of this document may be the subject of
patent rights. CENELEC shall not be held responsible for identifying any or all such patent rights.
This document is read in conjunction with CLC IEC/TS 63291-2:2025.
Any feedback and questions on this document should be directed to the users’ national committee. A
complete listing of these bodies can be found on the CENELEC website.
Endorsement notice
The text of the International Technical Specification IEC/TS 63291-1:2023 was approved by CENELEC
as a European Technical Specification without any modification.
In the official version, for Bibliography, the following notes have to be added for the standard indicated:
IEC 60633:2019 NOTE Approved as EN IEC 60633:2019 (not modified)
IEC 61660-1:1997 NOTE Approved as EN 61660-1:1997 (not modified)
IEC 61000-1-2 NOTE Approved as EN 61000-1-2
IEC 61000-4-7 NOTE Approved as EN 61000-4-7
IEC 61850 (series) NOTE Approved as EN 61850 (series)
Annex ZA
(normative)
Normative references to international publications
with their corresponding European publications
The following documents are referred to in the text in such a way that some or all of their content
constitutes requirements of this document. For dated references, only the edition cited applies. For
undated references, the latest edition of the referenced document (including any amendments) applies.
NOTE 1 Where an International Publication has been modified by common modifications, indicated by (mod),
the relevant EN/HD applies.
NOTE 2 Up-to-date information on the latest versions of the European Standards listed in this annex is available
here: www.cencenelec.eu.
Publication Year Title EN/HD Year
IEC 60909 series Short-circuit currents in three-phase AC EN 60909 series
systems
IEC 61975 2010 High-voltage direct current (HVDC) EN 61975 2010
installations - System tests
+ A1 2016 + A1 2017
+ A2 2022 + A2 2022
IEC 62271-100 - High-voltage switchgear and controlgear - EN IEC 62271-100 -
Part 100: Alternating-current circuit-
breakers
IEC 62271-102 - High-voltage switchgear and controlgear - EN IEC 62271-102 -
Part 102: Alternating current disconnectors
and earthing switches
IEC 62747 2014 Terminology for voltage-sourced converters EN 62747 2014
(VSC) for high-voltage direct current
(HVDC) systems
+ A1 2019 + A1 2019
IEC/TS 63014-1 - High voltage direct current (HVDC) power - -
transmission - System requirements for DC-
side equipment - Part 1: Using line-
commutated converters
IEC/TS 63291-2 2023 High voltage direct current (HVDC) grid CLC IEC/TS 63291-2 2025
systems and connected converter stations -
Guideline and parameter lists for functional
specifications - Part 2: Parameter lists
ISO/IEC 25010 2011 Systems and software engineering_- - -
Systems and software Quality
Requirements and Evaluation (SQuaRE)_-
System and software quality models

IEC TS 63291-1 ®
Edition 1.0 2023-09
TECHNICAL
SPECIFICATION
colour
inside
High voltage direct current (HVDC) grid systems and connected converter

stations – Guideline and parameter lists for functional specifications –

Part 1: Guideline
INTERNATIONAL
ELECTROTECHNICAL
COMMISSION
ICS 29.200; 29.240.01 ISBN 978-2-8322-7571-9

– 2 – IEC TS 63291-1:2023 © IEC 2023
CONTENTS
FOREWORD . 7
INTRODUCTION . 9
1 Scope . 10
2 Normative references . 10
3 Terms, definitions and abbreviated terms . 11
3.1 Terms and definitions . 11
3.2 Abbreviated terms . 16
4 Coordination of HVDC grid and AC systems . 16
4.1 About HVDC grids . 16
4.2 HVDC grid structure . 17
4.3 Purpose of the HVDC grid and power network diagram . 18
4.4 AC/DC power flow optimisation . 19
4.5 Converter operational functions . 20
4.5.1 General . 20
4.5.2 Basic operation functions – Converter normal operation state . 20
4.5.3 Basic operation functions – Converter abnormal operation state . 22
4.5.4 Ancillary services . 23
5 HVDC grid characteristics . 28
5.1 HVDC circuit topologies . 28
5.1.1 Availability and reliability . 28
5.1.2 Basic characteristics and nomenclature . 28
5.1.3 Attributes of HVDC grids or HVDC grid subsystems . 32
5.1.4 Attributes of an HVDC station . 33
5.2 Connection modes . 34
5.3 Grid operating states . 34
5.3.1 General . 34
5.3.2 Normal state . 35
5.3.3 Alert state . 35
5.3.4 Emergency state . 35
5.3.5 Blackout state . 35
5.3.6 Restoration . 35
5.4 DC voltages . 35
5.4.1 General . 35
5.4.2 Nominal DC system voltage . 35
5.4.3 Steady-state DC pole voltage . 36
5.4.4 Temporary DC pole voltage . 36
5.4.5 DC neutral bus voltage . 37
5.5 Insulation coordination . 39
5.6 Short-circuit characteristics . 39
5.6.1 Calculation of short-circuit currents in HVDC grids . 39
5.6.2 Short-circuit current design requirements . 41
5.7 Steady-state voltage and current distortions . 41
5.7.1 Emissions and impacts . 41
5.7.2 Rights and obligations of a connectee . 42
5.7.3 Similarities between HVDC grids and AC networks . 43
5.7.4 Voltage and current distortion limits . 44

IEC TS 63291-1:2023 © IEC 2023 – 3 –
5.7.5 Allocation of limits to individual connectees . 45
5.7.6 Frequency-dependent DC system impedance . 45
5.8 DC system restoration. 46
5.8.1 General . 46
5.8.2 Post-DC fault recovery . 46
5.8.3 Restoration from blackout . 46
6 HVDC grid control . 47
6.1 Closed-loop control functions . 47
6.1.1 General . 47
6.1.2 Core control functions . 47
6.1.3 Coordinating control functions . 47
6.2 Controller hierarchy . 48
6.2.1 General . 48
6.2.2 Internal converter control . 49
6.2.3 DC node voltage control . 49
6.2.4 Coordinated HVDC grid control . 50
6.2.5 AC/DC grid control . 52
6.3 Propagation of information . 53
6.4 Open-loop controls. 55
6.4.1 Coordination of connection modes between HVDC stations and their
PoC-DC . 55
6.4.2 Operating sequences for HVDC grid installations . 56
6.4.3 Post-DC fault recovery . 56
7 HVDC grid protection . 57
7.1 General . 57
7.2 DC fault separation . 58
7.3 Protection system related installations and equipment . 58
7.3.1 AC/DC converter station . 58
7.3.2 HVDC grid topology and equipment . 59
7.4 HVDC grid protection zones . 59
7.4.1 General . 59
7.4.2 Permanent stop P . 62
7.4.3 Permanent stop PQ . 64
7.4.4 Temporary stop P . 65
7.4.5 Temporary stop PQ . 68
7.4.6 Continued operation . 69
7.4.7 Example of a protection zone matrix . 71
7.5 DC protection . 72
7.5.1 General . 72
7.5.2 DC converter protections . 73
7.5.3 HVDC grid protections . 73
7.5.4 HVDC grid protection communication . 75
8 AC/DC converter stations . 75
8.1 Purpose . 75
8.2 AC/DC converter station types . 75
8.2.1 General . 75
8.2.2 AC/DC converter station type 1 (AC/DC type 1) . 75
8.2.3 AC/DC converter station type 2 (AC/DC type 2) . 75
8.2.4 AC/DC converter station type 3 (AC/DC type 3) . 76

– 4 – IEC TS 63291-1:2023 © IEC 2023
8.2.5 AC/DC converter station type 4 (AC/DC type 4) . 76
8.2.6 AC/DC converter station type 5 (AC/DC type 5) . 76
8.3 Overall requirements . 76
8.3.1 Robustness of AC/DC converter stations . 76
8.3.2 Availability and reliability . 77
8.3.3 Active power reversal . 77
8.4 Main circuit design . 77
8.4.1 General characteristics . 77
8.4.2 DC side . 79
8.4.3 AC side. 87
8.5 HVDC grid control and protection interface . 88
8.6 Controls . 88
8.6.1 General . 88
8.6.2 Automated vs manual operation . 88
8.6.3 Control modes and support of coordination . 89
8.6.4 Limitation strategies . 89
8.6.5 Operating sequences for AC/DC converter stations . 89
8.6.6 Dynamic behaviour . 91
8.7 Protection . 92
8.7.1 General . 92
8.7.2 Configuration requirements . 92
8.7.3 Function requirements . 93
8.7.4 Fault separation strategy for faults inside the AC/DC converter station . 94
8.7.5 Coordination of the DC protection with the HVDC grid . 95
8.7.6 Example for coordination of the DC protection with the HVDC grid . 95
9 HVDC grid installations . 97
9.1 General . 97
9.2 DC switching station . 100
9.2.1 Purpose . 100
9.2.2 Overall requirements . 100
9.2.3 Main circuit design . 100
9.2.4 HVDC grid control and protection interface . 111
9.2.5 Controls . 112
9.2.6 Protection . 113
9.3 HVDC transmission lines. 115
9.3.1 Purpose . 115
9.3.2 Overall requirements . 115
9.3.3 Main circuit design . 116
9.3.4 HVDC grid control and protection interface . 119
9.3.5 Controls . 119
9.3.6 Protection . 119
9.4 DC/DC converter stations . 120
10 Studies and associated models . 121
10.1 General . 121
10.2 Description of studies . 121
10.2.1 General . 121
10.2.2 HVDC grid planning studies . 121
10.2.3 HVDC grid design studies . 122
10.2.4 HVDC grid extension studies . 122

IEC TS 63291-1:2023 © IEC 2023 – 5 –
10.2.5 Studies for HVDC grid installation refurbishments and other
modifications . 122
10.3 Models and interfaces . 123
10.3.1 General . 123
10.3.2 Model interfaces and integration compatibility . 123
10.3.3 Model capability . 123
10.3.4 Model format . 124
10.3.5 Model maintenance and portability . 124
10.3.6 Model aggregation . 124
10.3.7 Model testing and validation . 124
11 Testing . 125
11.1 General . 125
11.2 Off-site testing . 125
11.2.1 General . 125
11.2.2 Factory system tests . 126
11.3 On-site testing . 131
Bibliography . 132

Figure 1 – Definition of the point of connection-AC and the point of connection-DC at
an AC/DC converter station . 12
Note 2 to entry: See Figure 2 – Rigid bipolar HVDC system . 14
Figure 2 – Rigid bipolar HVDC system . 15
Figure 3 – Schematic structure of an HVDC grid . 18
Figure 4 – Example of a PQ-diagram showing the active vs reactive power exchange
capability of an AC/DC converter station for a given AC voltage level . 19
Figure 5 – Generic AC over- and under voltage ride through profile of an AC/DC
converter station . 23
Figure 6 – Example of an active power frequency response capability of an AC/DC
converter station in frequency sensitive mode (FSM) with zero deadband and
insensitivity with a positive active power setpoint; FSM in this figure shall be
understood as FCR . 24
Figure 7 – Example of an HVDC grid in 2DCe topology with different AC/DC converter
station topologies . 31
Figure 8 – Operating states. 35
Figure 9 – Generic temporary DC pole to earth voltage profiles in HVDC grids . 37
Figure 10 – Generic neutral bus voltage profile . 39
Figure 11 – Standard approximation function . 41
Figure 12 – Equivalent circuit, defining the relationship between voltage and current
distortions . 42
Figure 13 – Disturbance level . 43
Figure 14 – Planning level and headroom . 44
Figure 15 – General controller hierarchy with typical time ranges of operation . 48
Figure 16 – Typical DC node voltage control modes (illustration in DC voltage/power
plane) . 50
Figure 17 – Generation of final converter schedules including converter control modes
and its parameters . 54
Figure 18 – Propagation of switching commands to individual HVDC stations . 55

– 6 – IEC TS 63291-1:2023 © IEC 2023
Figure 19 – Typical operating sequences for transitions between operating states of
HVDC grid, HVDC grid subsystem or HVDC grid installation . 56
Figure 20 – Example illustrating the concept of HVDC grid protection zones in HVDC

grids . 61
Figure 21 – Example of voltage and current traces in the event of "permanent stop" . 63
Figure 22 – Example voltage and current traces in the event of "temporary stop P" . 67
Figure 23 – Example voltage and current traces in the event of "continued operation" . 70
Figure 24 – Example of an HVDC grid protection zone layout . 72
Figure 25 – AC/DC converter station types in the U/I diagram. 76
Figure 26 – Example of a BRO AC/DC converter station with connected BRZ DC
switching station. The AC/DC converter station is of bipolar topology. Its adjacent DC
switching station connects two bipolar transmission circuits with DMR in this example . 80
Figure 27 – Operating states and transitions for AC/DC converter stations . 89
Figure 28 – Example illustrating the coordination of the DC protection of AC/DC
converter station 1 with the HVDC grid . 97
Figure 29 – Example of a BRZ DC switching station. The DC switching station
connects two bipolar transmission circuits with DMR and an AC/DC converter station
of bipolar topology . 103
Figure 30 – Example test environment based on complete C&P equipment

represented as hardware . 127
Figure 31 – Example test environment partly based on C&P equipment as hardware
and the remaining C&P equipment as functional software-in-the-loop model with two
alternatives for representing the HVDC grid controller . 128
Figure 32 – Example test environment based on complete C&P equipment
represented as functional software-in-the-loop model . 129
Figure 33 – Example test environment dedicated to test the HVDC grid controller,
based on complete C&P equipment represented as functional software-in-the-loop
model and HVDC grid controller as hardware . 130

Table 1 – Nomenclature of HVDC circuit topologies . 29
Table 2 – HVDC circuit topologies – HVDC grid characteristics . 29
Table 3 – HVDC circuit topologies – HVDC station characteristics at a PoC . 30
Table 4 – DC fault separation concepts of HVDC grids or parts thereof defined at a

PoC-AC or PoC-DC respectively . 61
Table 5 – HVDC grid protection zone matrix . 71
Table 6 – DC Connection modes of an AC/DC converter station . 81
Table 7 – DC circuit re-configuration requirements. 82
Table 8 – Example protection coordination of AC/DC converter station 1 and HVDC
grid (for main and backup concept including the separation concept and the FSD) . 96
Table 9 – Functions changing operating states . 98
Table 10 – Functions of grid operation . 99
Table 11 – Protective functions . 99
Table 12 – Connection modes of the bipolar DC SU of Figure 29 connecting a PoC-DC
of an HVDC transmission line . 105
Table 13 – Connection modes of the bipolar DC SU of Figure 29 connecting a PoC-DC

of an AC/DC converter station (x = 1) . 106
Table 14 – Normally used DC circuit reconfiguration time requirements for the DC SU
example of Figure 29 (PoC-DC) . 106

IEC TS 63291-1:2023 © IEC 2023 – 7 –
INTERNATIONAL ELECTROTECHNICAL COMMISSION
____________
HIGH VOLTAGE DIRECT CURRENT (HVDC) GRID SYSTEMS AND
CONNECTED CONVERTER STATIONS – GUIDELINE AND PARAMETER
LISTS FOR FUNCTIONAL SPECIFICATIONS –

Part 1: Guideline
FOREWORD
1) The International Electrotechnical Commission (IEC) is a worldwide organization for standardization comprising
all national electrotechnical committees (IEC National Committees). The object of IEC is to promote international
co-operation on all questions concerning standardization in the electrical and electronic fields. To this end and
in addition to other activities, IEC publishes International Standards, Technical Specifications, Technical Reports,
Publicly Available Specifications (PAS) and Guides (hereafter referred to as “IEC Publication(s)”). Their
preparation is entrusted to technical committees; any IEC National Committee interested in the subject dealt with
may participate in this preparatory work. International, governmental and non-governmental organizations liaising
with the IEC also participate in this preparation. IEC collaborates closely with the International Organization for
Standardization (ISO) in accordance with conditions determined by agreement between the two organizations.
2) The formal decisions or agreements of IEC on technical matters express, as nearly as possible, an international
consensus of opinion on the relevant subjects since each technical committee has representation from all
interested IEC National Committees.
3) IEC Publications have the form of recommendations for international use and are accepted by IEC National
Committees in that sense. While all reasonable efforts are made to ensure that the technical content of IEC
Publications is accurate, IEC cannot be held responsible for the way in which they are used or for any
misinterpretation by any end user.
4) In order to promote international uniformity, IEC National Committees undertake to apply IEC Publications
transparently to the maximum extent possible in their national and regional publications. Any divergence between
any IEC Publication and the corresponding national or regional publication shall be clearly indicated in the latter.
5) IEC itself does not provide any attestation of conformity. Independent certification bodies provide conformity
assessment services and, in some areas, access to IEC marks of conformity. IEC is not responsible for any
services carried out by independent certification bodies.
6) All users should ensure that they have the latest edition of this publication.
7) No liability shall attach to IEC or its directors, employees, servants or agents including individual experts and
members of its technical committees and IEC National Committees for any personal injury, property damage or
other damage of any nature whatsoever, whether direct or indirect, or for costs (including legal fees) and
expenses arising out of the publication, use of, or reliance upon, this IEC Publication or any other IEC
Publications.
8) Attention is drawn to the Normative references cited in this publication. Use of the referenced publications is
indispensable for the correct application of this publication.
9) Attention is drawn to the possibility that some of the elements of this IEC Publication may be the subject of patent
rights. IEC shall not be held responsible for identifying any or all such patent rights.
IEC TS 63291-1 has been prepared by IEC technical committee TC 115: High Voltage Direct
Current (HVDC) transmission for DC voltages above 100 kV. It is a Technical Specification.
The text of this Technical Specification is based on the following documents:
Draft Report on voting
115/319/DTS 115/328A/RVDTS
Full information on the voting for its approval can be found in the report on voting indicated in
the above table.
The language used for the development of this Technical Specification is English.
This Technical Specification is to be used in conjunction with IEC TS 63291-2:2023.

– 8 – IEC TS 63291-1:2023 © IEC 2023
A list of all parts in the IEC 63291 series, published under the general title High voltage direct
current (HVDC) grid systems and connected converter stations – Guideline and parameter lists
for functional specifications, can be found on the IEC website.
This document was drafted in accordance with ISO/IEC Directives, Part 2, and developed in
accordance with ISO/IEC Directives, Part 1 and ISO/IEC Directives, IEC Supplement, available
at www.iec.ch/members_experts/refdocs. The main document types developed by IEC are
described in greater detail at www.iec.ch/standardsdev/publications.
The committee has decided that the contents of this document will remain unchanged until the
stability date indicated on the IEC website under webstore.iec.ch in the data related to the
specific document. At this date, the document will be
• reconfirmed,
• withdrawn,
• replaced by a revised edition, or
• amended.
IMPORTANT – The "colour inside" logo on the cover page of this document indicates
that it contains colours which are considered to be useful for the correct understanding
of its contents. Users should therefore print this document using a colour printer.

IEC TS 63291-1:2023 © IEC 2023 – 9 –
INTRODUCTION
In the preparation of this document, special care has been taken to, as far as possible, describe
the requirements in a technologically independent way. In order to achieve that, a function of
interest is described by a comprehensive set of parameters. The parameters are selected based
on a systematic analysis of physical phenomena relevant to achieve the requested functionality.
Reflecting the early stage of technology, the technical parameters need comprehensive
explanations and background information. This need is reflected in the dual character of the
content, which is presented in the two corresponding parts:
• IEC TS 63291-1, Guideline containing the explanations and the background information in
context with the parameter lists;
• IEC TS 63291-2, Parameter lists containing the essential lists of parameters and values
describing properties of the AC respectively DC system (operating conditions) and
parameters describing the performance of the newly installed component (performance
requirements).
IEC TS 63291-1 and IEC TS 63291-2 have the same structure to aid the reader.
At the time of writing there is no real-life multi-national, multi-vendor HVDC grid project to which
the guideline and parameter lists can be applied. Practical experiences in the near future are
expected to provide input for developing these guideline and parameter lists further.

– 10 – IEC TS 63291-1:2023 © IEC 2023
HIGH VOLTAGE DIRECT CURRENT (HVDC) GRID SYSTEMS AND
CONNECTED CONVERTER STATIONS – GUIDELINE AND PARAMETER
LISTS FOR FUNCTIONAL SPECIFICATIONS –

Part 1: Guideline
1 Scope
This document contains guidelines on planning, specification, and execution of multi-vendor
HVDC grid systems also referred to as HVDC grids. The terms "HVDC grid systems" or "HVDC
grids" are used in this document to describe HVDC systems for power transmission having more
than two HVDC stations connected to a common DC circuit. The DC circuit can be of radial or
meshed topology or a combination thereof. In this document, the term "HVDC grids" is used.
While this document focuses on requirements specific for HVDC grids, some requirements are
considered applicable to all HVDC systems in general, i.e., including point-to-point HVDC
systems. Existing IEC (e.g. IEC TR 63363-1 [1]), Cigre or other relevant documents have been
used for reference as far as possible.
Corresponding to electric power transmission applications, this document is applicable to high
voltage systems, i.e. those having typically nominal DC voltages higher than 50 kV with respect
to earth are considered in this document.
NOTE While the physical principles of DC networks are basically voltage independent, the technical options for
designing equipment get much wider with lower DC voltage levels, e.g. in case of converters or switchgear.
This document covers technical aspects of:
• coordination of HVDC grid and AC systems,
• HVDC grid characteristics,
• HVDC grid control,
• HVDC grid protection,
• AC/DC converter stations,
• HVDC grid installations, including DC switching stations and HVDC transmission lines,
• studies and associated models,
• testing.
Beyond the scope of this document, the following content is proposed for future work:
• DC/DC converter stations.
2 Normative references
The following documents are referred to in the text in such a way that some or all of their content
constitutes requirements of this document. For dated references, only the edition cited applies.
For undated references, the latest edition of the referenced document (including any
amendments) applies.
IEC 60909 (all parts), Short-circuit currents in three-phase AC systems

IEC TS 63291-1:2023 © IEC 2023 – 11 –
IEC 61975:2010, High-voltage direct current (HVDC) installations – System tests
IEC 61975:2010/AMD1:2016
IEC 61975:2010/AMD2:2022
IEC 62271-100, High-voltage switchgear and controlgear – Part 100: Alternating-current
circuit-breakers
IEC 62271-102, High-voltage switchgear and controlgear – Part 102: Alternating current
disconnectors an
...