TC 115 - High Voltage Direct Current (HVDC) transmission for DC voltages above 100 kV

IEC TS 63336:2024, which is a technical specification, applies to the commissioning of voltage-sourced converter (VSC) high voltage direct current (HVDC) systems which consist of two converter stations and the connecting HVDC transmission line.
The tests are generally applied to all HVDC configurations and could require addition or deletion to match the given solution.
This document provides guidance on the planning of commissioning activities. The commissioning described in this document is implemented through on-site testing on the whole system functionality, including testing on the subsystem and system. This document provides the scope, procedures and acceptance criteria of the tests.
Factory system tests, on-site equipment tests, electrode tests, and trial operation are not included in this document.

IEC TR 63127:2019(E) focuses on the system design of converter stations. It is applicable to point-­to-­point and back-to-back HVDC systems based on line-commutated converter (LCC) technology. This document provides guidance and supporting information on the procedure for system design and the technical issues involved in the system design of HVDC transmission projects for both purchaser and potential suppliers. It can be used as the basis for drafting a procurement specification and as a guide during project implementation.

IEC TR 63463:2024 provides guidelines for the general procedure for performing life assessment for an HVDC converter station. Following this, a more detailed description of performance issues of the thyristor based HVDC systems is given and the life assessment measures of equipment and guidelines for accessing the techno-economic life of equipment are given. This document also deals with information for specification of refurbishing HVDC system and the testing of the refurbished and replaced equipment. Lastly, this document outlines environmental issues and regulatory issues involved in the life assessment and concludes with a financial analysis of the refurbishment options.

IEC TS 63471:2023 provides a recommended DC voltage series for HVDC grids with a DC voltage above 1,5 kV. It concerns the selection of a nominal DC voltage of multi-terminal HVDC power transmission and distribution systems and meshed HVDC networks, grids, rather than a rated DC voltage or highest DC voltage.
There is no stringent requirement to consider this DC voltage series for the DC voltage selection for any stand-alone (not forming part of DC Grid) HVDC projects, e.g. a point-to-point HVDC power transmission and distribution system. However, in order to facilitate the later progression towards larger HVDC systems in the future the use of standardized DC voltages is very useful. At later stages, with multi-terminal systems and meshed HVDC grids, the use of harmonized voltages will indeed become essential in order to optimize both capital and operational costs. Also, for entirely new projects, system planning should include this outlook and can benefit from the use of the recommended DC voltage series.

IEC TS 63291-1:2023 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.

IEC TS 63291-2:2023 defines aspects 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 the 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.

IEC TR 63065:2017(E) provides general guidance on basic principles and general proposals for the safe and economic operation and maintenance of an LCC converter station.
These guidelines are based on the operation and maintenance practices that have been used successfully during the last decades at HVDC converter stations all over the world, and can be referred to by new HVDC users to optimize operation and maintenance policy and assist in performing the operation and maintenance work.
This document focuses only on the operation and maintenance of the equipment inside an LCC converter station, including back-to-back HVDC systems. The operation and maintenance of HVDC overhead transmission lines, HVDC cables and voltage sourced converter (VSC) are not covered by this document.

IEC TR 63363-1:2022(E) is to present the "state of the art" with respect to general guidance on the steady-state performance demands of VSC HVDC transmission systems. It concerns the steady-state performance of two-terminal VSC HVDC transmission systems utilizing converters with power flow capability in both directions.
Different configurations of a VSC HVDC transmission system are covered in this document, including the symmetrical monopolar, asymmetrical monopolar, bipolar with earth return, bipolar with dedicated metallic return and rigid bipolar configurations.
There are many variations between different VSC HVDC transmission systems. This document does not consider these in detail; consequently, it cannot be used directly as a specification for a particular project, but rather to provide the general basis for the system steady-state performance demands.
Normally, the performance specifications are based on a complete system including two VSC HVDC converter stations. However, sometimes a VSC HVDC transmission system can also be separately specified and purchased from multiple vendors instead of single turnkey vendor. In such cases, due consideration can be given to the coordination of each part with the overall VSC HVDC system performance objectives and the interface of each with the system can be clearly defined. The major components of the VSC HVDC transmission system are presented in IEC 62747.
Referring to IEC 62747, an HVDC substation/converter station is defined as that part of the VSC HVDC transmission system which consists of one or more VSC converter units installed in a single location together with buildings, reactors, filters, reactive power supply, control, monitoring, protective, measuring and auxiliary equipment. The AC substations are not covered in this document.
This document provides guidance and supporting information on the procedure for system design and the technical issues involved in the system design of VSC HVDC transmission projects for both owners and contractors. This document can be used as the basis for drafting a procurement specification and as a guide during project implementation.

IEC TR 62681:2022 provides general guidance on the electromagnetic environment issues of HVDC overhead transmission lines. It concerns the major parameters adopted to describe the electromagnetic properties of an HVDC overhead transmission line, including electric fields, ion current, magnetic fields, radio interference, and audible noise generated as a consequence of such effects. If the evaluation method and/or criteria of electromagnetic properties are not yet regulated, engineers in different countries can refer to this document to:
- support/guide the electromagnetic design of HVDC overhead transmission lines,
- limit the influence on the environment within acceptable ranges, and
- optimize engineering costs.

IEC TS 62344:2022 applies to the design of earth electrode stations for high-voltage direct current (HVDC) links. It is intended to provide necessary guidelines, limits, and precautions to be followed during the design of earth electrodes to ensure safety of personnel and earth electrodes, and reduce any significant impacts on DC power transmission systems and the surrounding environment. This edition includes the following significant technical changes with respect to the previous edition:
- Changed the requirement of earthing resistance limit for short-time unipolar earth system in 5.1.3.
- Corrected the coefficient before ρs from 0,015 9 to 0,008 in touch voltage limit calculation formula (3) in 5.1.5.
- Deleted the analytical calculation formulas of earthing resistance for sea and shore electrodes in 6.1.3.
- Changed the current density limit from 100 A/m2 to 40 A/m2 ~ 50 A/m2 for the sea electrodes that are not accessible to human beings or to marine fauna in 6.1.7.
- Extended some detailed technical requirements for the measurement of ground/water soil parameters in 6.2.5.
- Reformulated the types and characteristics of electrode element material for sea and shore electrodes in 6.3.2.
- Added an informative Annex B: Earth electrode design process.
- Added an informative Annex C: Test results of human body resistance.
- Deleted the formula for calculating the average soil resistivity using harmonic mean when processing the measurement data in D.2.6 of Annex D.
- Extended some detailed technical requirements of electrode online monitoring system in Annex H.
- CIGRE 675:2017 is added to the bibliography.
- Terminology and way of expressions are modified using more commonly used terms in the HVDC electrode design industries and English-speaking countries, so as to make the readers understand the content more easily.

IEC TR 63179-1:2020 (E) provides guidelines for the selection of a high-voltage directive current (HVDC) system with line-commutated converters (LCC), hereafter referred to as HVDC system, for the purposes of HVDC system planning. It covers the guidelines on the requirements for integrating HVDC systems in AC power networks, selection of rated voltage and power, overloads, circuit configuration, expandability, comparison of technical, economic, regulatory, political, social and environmental factors, etc.
This document is applicable for planning an HVDC system. This guideline is not exhaustive and it is possible that there will be other specific aspects, particular to a specific HVDC project, which will also need to be considered.

IEC/TS 61973:2012(E) applies to the specification and evaluation of outdoor audible noise from high voltage direct current (HVDC) substations. It is intended to be primarily for the use of the utilities and consultants who are responsible for issuing technical specifications for new HVDC projects with and evaluating designs proposed by prospective contractors. It is primarily intended for HVDC projects with line-commutated converters. Part of this technical specification can also be used for the same purpose for HVDC projects using voltage sourced converters, and for flexible a.c. transmission systems (FACTS) devices such as static Var compensators (SVCs) and static synchronous compensators (STATCOMs).

IEC TR 62672:2018(E) applies to all line-commutated and voltage-sourced high-voltage direct current (HVDC) transmission systems used for power exchange in utility systems. The purpose of this document is to define a standardized reporting protocol so that data collected from different HVDC transmission systems can be compared on an equitable basis. This document covers point-to-point transmission systems, back-to-back interconnections and multi-terminal transmission systems.

IEC TS 63014-1:2018(E) is intended to provide an overall and consistent set of guidelines to facilitate the specification of equipment for the DC-side of a high-voltage direct current (HVDC) system using line-commutated converters. For point-to-point HVDC transmission systems, this document covers all DC-side equipment located between the converter valves and the DC overhead line or cable termination, excluding the converter valves themselves. For back-to-back HVDC systems, this document covers all DC-side equipment excluding the converter valves themselves.

IEC TR 62978:2017(E) gives guidelines on the current asset management perspectives for HVDC installations based on best practices of asset owners, operators, users, original equipment manufacturers and regulators within the power industry. This document covers HVDC systems with Line-Commutated Converters (LCC) and can be generally applied to Voltage Sourced Converters (VSC), not including specific equipment or sub-equipment required under VSC. This document provides base guidelines on fundamental aspects and prudent practices to be considered by stake holders in managing HVDC assets. Compliance to additional requirements and recommendations stipulated in this document by the supplier or OEM are non-obligatory, unless explicitly specified by the customer.

IEC TR 62681:2014 provides general guidance on the electromagnetic environment issues of HVDC transmission lines. It concerns the major parameters adopted to describe the electromagnetic environment of a High-Voltage Direct Current (HVDC) transmission line, including electric fields, ion current, magnetic fields radio interference, and audible noise generated as a consequence of such effects. Engineers in different countries can refer to this Technical Report to ensure the safe operation of HVDC transmission lines, limit the influence on the environment within acceptable ranges, and optimize engineering costs.

IEC/TS 62344:2013(E) applies to the design of earth electrode stations for high-voltage direct current (HVDC) links. It is intended to provide necessary guidelines, limits, and precautions to be followed during the design of earth electrodes to ensure safety of personnel and earth electrodes and prevent any significant impact they may exert on d.c. power transmission systems and the surrounding environment. This technical specification cancels and replaces IEC/PAS 62344 published in 2007. This first edition constitutes a technical revision.

IEC/TS 62672-1:2013(E) applies to all line-commutated high-voltage direct current (HVDC) transmission systems used for power exchange in utility systems. HVDC stations with voltage sourced converters (VSC) are not covered. The purpose of this part of IEC 62672 is to define a standardized reporting protocol so that data collected from different HVDC transmission systems can be compared on an equitable basis. It covers point-to-point transmission systems, back-to-back interconnections and multi-terminal transmission systems. For point-to-point systems and back-to-back interconnections, i.e. two-terminal systems, statistics are to be reported based on the total transmission capability from the sending end to the receiving end measured at a given point. If, however, the two terminals are operated by different users/owners, or are composed of equipment of different vintage or of equipment from different suppliers, statistics can be reported on an individual station basis if so desired by those responsible for reporting. In such a case, the outage should only be reported under the originating converter station taking care not to report the same event twice. For distributed multi-terminal systems, i.e. systems with more than two terminals, statistics are to be reported separately for each converter station based on its own individual capability.

Provides a guide for the design of electrode stations for HVDC links intended for ground return. This design guide was prepared by the CIGRÉ Working Group 14.21: HVDC Ground Electrode Design during the period 1995-1998.