SIST EN IEC 61803:2026
(Main)Determination of power losses in high-voltage direct current (HVDC) converter stations (IEC 61803:2026)
- Abstract
This document applies to all high-voltage direct current (HVDC) converter stations with linecommutated converters (LCC) as well with voltage-sourced converters (VSC) used for power exchange (power transmission or back-to-back installation) in utility systems. For linecommutated converters (LCC), this document presumes the use of 12-pulse thyristor converters but can, with due care, also be used for 6-pulse thyristor converters.
Where VSC is referred to in this document, it is assumed to be of the MMC-type or similar, with very low harmonic generation. It is important to treat other types of VSC as appropriate.
In some applications, synchronous compensators, static var compensators (SVC), or static synchronous compensator (STATCOM) are connected to the AC bus of the HVDC converter station. The loss determination procedures for such equipment are not included in this document.
This document presents a set of standard procedures for determining the total losses of an HVDC converter station, except for VSC valves which are covered by the IEC 62751 series.
The procedures cover all parts, except as noted above, and address no-load operation and operating losses together with their methods of calculation which use, wherever possible, measured parameters.
Converter station designs employing novel components or circuit configurations compared to the typical design assumed in this document, or designs equipped with unusual auxiliary circuits that can affect the losses, are assessed on their own merits.
- Status
- Published
- Public Enquiry End Date
- 30-Jul-2025
- Publication Date
- 12-Oct-2026
- Technical Committee
- MOV - Measuring equipment for electromagnetic quantities
- Current Stage
- 6060 - National Implementation/Publication (Adopted Project)
- Start Date
- 28-Jul-2026
- Due Date
- 02-Oct-2026
- Completion Date
- 13-Oct-2026
SIST EN IEC 61803:2026 is the Slovenian standard for determining power losses in high-voltage direct current (HVDC) converter stations. It gives a common calculation method for line-commutated converter (LCC) and voltage-sourced converter (VSC) stations used for power transmission or back-to-back installation in utility systems, so suppliers and purchasers can compare losses on the same basis. The document focuses on summing equipment losses under defined operating conditions, using measured data wherever possible.
What does SIST EN IEC 61803:2026 specify?
SIST EN IEC 61803:2026 applies to HVDC converter stations with LCC and VSC used for power exchange in utility systems. For LCC, it assumes 12-pulse thyristor converters but can also be used for 6-pulse thyristor converters with due care. For VSC, the text assumes a modular multilevel converter (MMC) type or similar with very low harmonic generation.
It covers standard procedures for total station loss determination, except for VSC valves, which are covered by IEC 62751. It also leaves out loss-determination procedures for synchronous compensators, static var compensators (SVC), and static synchronous compensators (STATCOM) connected to the AC bus. Designs with novel components, unusual auxiliary circuits, or non-typical arrangements are to be assessed on their own merits.
| Annex | What it covers |
|---|---|
| Annex A | Calculation of harmonic currents and voltages for LCC stations |
| Annex B | Typical station losses |
| Annex C | An illustration of HVDC converter station loss evaluation |
The document is organized into clauses on scope, normative references, terms and symbols, overview, and equipment-loss determination, followed by informative annexes.
What are the key requirements of SIST EN IEC 61803:2026?
SIST EN IEC 61803:2026 sets a calculation method for station losses by adding the losses of each relevant item of equipment. Clause 4 explains why direct whole-station measurement is often too inaccurate at HVDC voltage levels, because the station losses are usually a small fraction of transmitted power. In practice, this means loss guarantees are normally checked from component data, not from one large input-output measurement.
Reference conditions matter to every calculation
Clause 4.2 fixes the ambient reference conditions used for loss evaluation. The outdoor dry-bulb reference temperature is 20 °C, the standard air pressure is 101.3 kPa corrected for altitude above 1000 m, and coolant temperature and flow rate are defined by the purchaser and supplier. If a wet-bulb temperature is needed and none is stated, 14 °C is recommended.
This matters because losses change with temperature, coolant, and altitude. If two bids use different reference conditions, the numbers are not directly comparable.
Operating losses and no-load losses are treated separately
Clause 4.3 separates operating losses from no-load operation losses. Operating losses are determined at the load levels specified by the purchaser, or at rated load if none are given. No-load operation means the transformers are energized, the converters are blocked, and filters and reactive compensation are disconnected unless they are needed to sustain zero-load operation.
For VSC stations, reactive power is assumed to be zero unless otherwise specified. In practice, this tells the reader which equipment must be energized for each operating point and which auxiliary systems must be included.
LCC valve losses are built up component by component
Clause 5.1 gives a detailed loss model for thyristor valves in LCC stations. It covers conduction loss, spreading loss, other conduction losses, DC voltage-dependent loss, two damping-loss terms, turn-off loss, reactor loss, temperature effects, and no-load operation loss per valve. The calculations use measured or production data where possible, including thyristor characteristics, valve resistance, inductance, stored charge, and coolant temperature.
The practical point is that valve loss is not taken as a single fixed percentage. The standard expects the user to trace each loss mechanism and correct values to the operating junction temperature.
Transformer losses follow established transformer test methods
Clause 5.2 treats converter transformer losses. No-load losses are determined according to IEC 60076-1, and operating losses are the sum of core losses and current-dependent load losses. For LCC stations, harmonic currents are included in the load-loss calculation; for VSC stations, current total harmonic distortion (THD) below 5% may be treated like conventional AC transformer duty, while higher THD requires the harmonic spectrum to be specified.
This matters for transformer sizing and guarantees, because harmonics can raise the loss figure above simple fundamental-frequency calculations.
Filters, reactors, auxiliaries, and special equipment are handled separately
Clauses 5.3 to 5.7 cover AC filters, shunt capacitor banks, shunt reactors, DC smoothing reactors, and DC filters. Capacitor losses follow IEC 60871-1, reactor losses are based on factory-measured reactance and quality factor corrected to operating temperature, and the calculations use harmonic spectra up to the stated harmonic limits, typically 49 on the AC side and 48 on the DC side. This tells the reader that filter and reactor losses are not estimated only from nameplate ratings.
Clause 5.8 covers auxiliaries and station service losses. These losses are averaged over time, and loads used only for maintenance, short overloads, or transient disturbances are excluded. If shared feeders also supply equipment outside the supplier’s responsibility, that load is measured separately and subtracted.
Clauses 5.9 to 5.12 cover series filters, phase reactor losses, valve reactor losses, and other equipment. Losses of small items such as surge arresters, instrument transformers, switchgear bus-bars, and cables are neglected, while special equipment not covered by the typical station model is handled case by case.
Annexes support the calculations
Annex A gives the LCC harmonic current and voltage equations used in transformer, filter, and smoothing-reactor loss calculations. Annex C shows how no-load, load, and operating losses can be weighted for long-term energy-cost evaluation, which matters when the buyer wants a life-cycle view rather than a single operating point.
What terms does SIST EN IEC 61803:2026 define?
SIST EN IEC 61803:2026 uses a small set of operating terms to separate standby, no-load, and load-carrying losses.
- Auxiliary losses - the electric power needed to feed converter-station auxiliary loads.
- Equipment no-load operation losses - losses in energized equipment when the converters are blocked and the station is prepared for immediate pickup of load.
- Load level - the set of AC system and converter operating conditions at which the station is operating.
- Equipment operating losses - losses in an item of equipment at a given load level with the converters operating.
- Rated load - the load corresponding to nominal operating conditions, with nominal frequency, balanced voltages, and consistent tap-changer and filter settings.
- Total station no-load operation losses - the sum of all equipment no-load operation losses and the corresponding auxiliary losses.
- Total station operating losses - the sum of all equipment operating losses and the corresponding auxiliary losses at a particular load level.
- Station essential auxiliary load - an auxiliary load whose failure would affect conversion capability, or that must remain on during complete loss of AC power.
Who uses SIST EN IEC 61803:2026?
SIST EN IEC 61803:2026 is used by HVDC project owners, purchasers, suppliers, and designers who need a common way to declare and compare station losses. It is also used by transformer, reactor, filter, and valve manufacturers when they provide loss data for factory tests and bid documents.
In practice, the document supports bid evaluation, loss guarantees, factory verification, and long-term operating-cost studies for utility HVDC schemes.
What changed in SIST EN IEC 61803:2026 from the previous edition?
SIST EN IEC 61803:2026 is stated to cancel and replace the second edition published in 2020. The stated technical changes are:
- HVDC stations with Voltage-Sourced Converters (VSC) technology are included.
- Clauses 5.1.8 and 5.8 were reviewed to reflect current thyristor production technology and the use of production records in loss calculations.
- The calculation of total station load losses in Annex C, cases D1 and D2, was corrected.
Which standards are used with SIST EN IEC 61803:2026?
SIST EN IEC 61803:2026 relies on transformer, reactor, capacitor, thyristor, and VSC terminology standards for its loss calculations.
| Standard | What it contributes |
|---|---|
| IEC 60076-1 | General transformer requirements and no-load losses |
| IEC 60076-6 | Reactor testing and reactor losses |
| IEC 60633 | HVDC vocabulary |
| IEC 60700-1:2015 | Thyristor valve electrical testing used in valve-loss data |
| IEC 60871-1 | Shunt capacitor loss determination |
| IEC 62747 | VSC terminology |
| IEC 62751 | VSC valve power losses, which are handled outside this document |
The bibliography also points to IEC TR 62001-5, IEC/IEEE 60076-57-129:2017, IEC 61000-4-7, IEC 62751-1, and IEC 62751-2 for related VSC, transformer, and harmonic topics.
What does the SIST EN IEC 61803:2026 document contain?
SIST EN IEC 61803:2026 contains calculation procedures, not just general guidance. The main body includes formulas for LCC thyristor valve losses, transformer losses, filter losses, reactor losses, auxiliary losses, and other equipment losses, together with the ambient and operating conditions that must be used.
The figures show typical one-pole HVDC equipment for LCC and VSC schemes, a simplified 12-pulse converter, a thyristor valve equivalent circuit, valve waveforms, the on-state characteristic, commutating inductance distribution, and reverse recovery. Annex A provides harmonic equations, Annex B gives typical loss ranges for LCC and VSC MMC stations, and Annex C gives worked loss-evaluation cases with time factors for standby and load operation.
Relations
- Effective Date
- 07-Jul-2026
- Effective Date
- 07-Jul-2026
- Effective Date
- 07-Jul-2026
- Effective Date
- 07-Jul-2026
- Effective Date
- 07-Jul-2026
- Effective Date
- 07-Jul-2026
- Effective Date
- 07-Jul-2026
- Effective Date
- 28-Jul-2026
- Effective Date
- 06-Feb-2024
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Frequently Asked Questions
SIST EN IEC 61803:2026 is a standard published by the Slovenian Institute for Standardization (SIST). Its full title is "Determination of power losses in high-voltage direct current (HVDC) converter stations (IEC 61803:2026)". This standard covers: This document applies to all high-voltage direct current (HVDC) converter stations with linecommutated converters (LCC) as well with voltage-sourced converters (VSC) used for power exchange (power transmission or back-to-back installation) in utility systems. For linecommutated converters (LCC), this document presumes the use of 12-pulse thyristor converters but can, with due care, also be used for 6-pulse thyristor converters. Where VSC is referred to in this document, it is assumed to be of the MMC-type or similar, with very low harmonic generation. It is important to treat other types of VSC as appropriate. In some applications, synchronous compensators, static var compensators (SVC), or static synchronous compensator (STATCOM) are connected to the AC bus of the HVDC converter station. The loss determination procedures for such equipment are not included in this document. This document presents a set of standard procedures for determining the total losses of an HVDC converter station, except for VSC valves which are covered by the IEC 62751 series. The procedures cover all parts, except as noted above, and address no-load operation and operating losses together with their methods of calculation which use, wherever possible, measured parameters. Converter station designs employing novel components or circuit configurations compared to the typical design assumed in this document, or designs equipped with unusual auxiliary circuits that can affect the losses, are assessed on their own merits.
This document applies to all high-voltage direct current (HVDC) converter stations with linecommutated converters (LCC) as well with voltage-sourced converters (VSC) used for power exchange (power transmission or back-to-back installation) in utility systems. For linecommutated converters (LCC), this document presumes the use of 12-pulse thyristor converters but can, with due care, also be used for 6-pulse thyristor converters. Where VSC is referred to in this document, it is assumed to be of the MMC-type or similar, with very low harmonic generation. It is important to treat other types of VSC as appropriate. In some applications, synchronous compensators, static var compensators (SVC), or static synchronous compensator (STATCOM) are connected to the AC bus of the HVDC converter station. The loss determination procedures for such equipment are not included in this document. This document presents a set of standard procedures for determining the total losses of an HVDC converter station, except for VSC valves which are covered by the IEC 62751 series. The procedures cover all parts, except as noted above, and address no-load operation and operating losses together with their methods of calculation which use, wherever possible, measured parameters. Converter station designs employing novel components or circuit configurations compared to the typical design assumed in this document, or designs equipped with unusual auxiliary circuits that can affect the losses, are assessed on their own merits.
SIST EN IEC 61803:2026 is classified under the following ICS (International Classification for Standards) categories: 29.200 - Rectifiers. Convertors. Stabilized power supply. The ICS classification helps identify the subject area and facilitates finding related standards.
SIST EN IEC 61803:2026 has the following relationships with other standards: It is inter standard links to SIST EN 60700-1:2015/A1:2022, SIST EN 60871-1:2014, SIST EN 60076-1:2012, SIST EN IEC 60633:2020, SIST EN 60700-1:2015, SIST EN 60076-6:2008, SIST EN 62747:2014, SIST EN 62751-2:2014/A1:2020, SIST EN IEC 61803:2021. Understanding these relationships helps ensure you are using the most current and applicable version of the standard.
SIST EN IEC 61803:2026 is available in PDF format for immediate download after purchase. The document can be added to your cart and obtained through the secure checkout process. Digital delivery ensures instant access to the complete standard document.
Standards Content (Sample)
SLOVENSKI STANDARD
01-november-2026
Ugotavljanje močnostnih izgub v visokonapetostnih enosmernih (HVDC)
pretvorniških postajah (IEC 61803:2026)
Determination of power losses in high-voltage direct current (HVDC) converter stations
(IEC 61803:2026)
Bestimmung der Leistungsverluste in Hochspannungsgleichstrom-
(HGÜ-)Stromrichterstationen mit netzgeführten Stromrichtern (IEC 61803:2026)
Détermination des pertes en puissance dans les postes de conversion en courant
continu à haute tension (CCHT) (IEC 61803:2026)
Ta slovenski standard je istoveten z: EN IEC 61803:2026
ICS:
29.200 Usmerniki. Pretvorniki. Rectifiers. Convertors.
Stabilizirano električno Stabilized power supply
napajanje
2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.
EUROPEAN STANDARD EN IEC 61803
NORME EUROPÉENNE
EUROPÄISCHE NORM July 2026
ICS 29.200 Supersedes EN IEC 61803:2020
English Version
Determination of power losses in high-voltage direct current
(HVDC) converter stations
(IEC 61803:2026)
Détermination des pertes en puissance dans les stations de Bestimmung der Leistungsverluste in
conversion en courant continu à haute tension (CCHT) Hochspannungsgleichstrom-(HGÜ-)Stromrichterstationen
(IEC 61803:2026) mit netzgeführten Stromrichtern
(IEC 61803:2026)
This European Standard was approved by CENELEC on 2026-06-30. CENELEC members are bound to comply with the CEN/CENELEC
Internal Regulations which stipulate the conditions for giving this European Standard the status of a national standard without any alteration.
Up-to-date lists and bibliographical references concerning such national standards may be obtained on application to the CEN-CENELEC
Management Centre or to any CENELEC member.
This European Standard exists in three official versions (English, French, German). A version in any other language made by translation
under the responsibility of a CENELEC member into its own language and notified to the CEN-CENELEC Management Centre has the
same status as the official versions.
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
© 2026 CENELEC All rights of exploitation in any form and by any means reserved worldwide for CENELEC Members.
Ref. No. EN IEC 61803:2026 E
European foreword
The text of document 22F/860/FDIS, future edition 3 of IEC 61803, prepared by SC 22F "Power
electronics for electrical transmission and distribution systems" of IEC/TC 22 "Power electronic
systems and equipment" was submitted to the IEC-CENELEC parallel vote and approved by
CENELEC as EN IEC 61803:2026.
The following dates are fixed:
• latest date by which the document has to be implemented at national (dop) 2027-07-31
level by publication of an identical national standard or by endorsement
• latest date by which the national standards conflicting with the (dow) 2029-07-31
document have to be withdrawn
This document supersedes EN IEC 61803:2020 and all of its amendments and corrigenda (if any).
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.
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 Standard IEC 61803:2026 was approved by CENELEC as a European
Standard without any modification.
In the official version, for Bibliography, the following notes have to be added for the standard indicated:
IEC 61000-4-7 NOTE Approved as EN 61000-4-7
IEC 62751 series NOTE Approved as EN 62751 series
IEC 62751-1 NOTE Approved as EN 62751-1
IEC 62751-2 NOTE Approved as EN 62751-2
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 60076-1 - Power transformers - Part 1: General EN 60076-1 -
IEC 60076-6 - Power transformers - Part 6: Reactors EN 60076-6 -
IEC 60633 - High-voltage direct current (HVDC) EN IEC 60633 -
transmission - Vocabulary
IEC 60700-1 2015 Thyristor valves for high voltage direct EN 60700-1 2015
current (HVDC) power transmission - Part
1: Electrical testing
+ AMD1 2021 + A1 2021
IEC 60871-1 - Shunt capacitors for a.c. power systems EN 60871-1 -
having a rated voltage above 1 000 V -
Part 1: General
IEC 62747 - Terminology for voltage-sourced EN 62747 -
converters (VSC) for high-voltage direct
current (HVDC) systems
IEC 61803 ®
Edition 3.0 2026-05
INTERNATIONAL
STANDARD
Determination of power losses in high-voltage direct current (HVDC) converter
stations
ICS 29.200 ISBN 978-2-8327-1202-3
IEC 61803:2026-05(en)
IEC 61803:2026 © IEC 2026
CONTENTS
FOREWORD . 3
1 Scope . 5
2 Normative references . 5
3 Terms, definitions and symbols . 6
3.1 Terms and definitions. 6
3.2 Symbols . 7
3.2.1 Common . 7
3.2.2 Line-commutated converters . 8
4 Overview . 8
4.1 General . 8
4.2 Ambient conditions . 12
4.2.1 General . 12
4.2.2 Outdoor standard reference temperature . 12
4.2.3 Coolant standard reference temperature . 12
4.2.4 Standard reference air pressure . 12
4.3 Operating parameters . 12
5 Determination of equipment losses . 13
5.1 Thyristor valve losses (LCC only) . 13
5.1.1 General . 13
5.1.2 Thyristor conduction loss per valve . 16
5.1.3 Thyristor spreading loss per valve . 17
5.1.4 Other conduction losses per valve . 19
5.1.5 DC voltage-dependent loss per valve. 19
5.1.6 Damping loss per valve (resistor-dependent term) . 20
5.1.7 Damping loss per valve (change of capacitor energy term) . 21
5.1.8 Turn-off losses per valve . 22
5.1.9 Reactor loss per valve . 22
5.1.10 Total valve losses . 23
5.1.11 Temperature effects . 23
5.1.12 No-load operation loss per valve . 24
5.2 Transformer losses . 24
5.2.1 General . 24
5.2.2 No-load operation losses . 24
5.2.3 Operating losses . 25
5.2.4 Auxiliary power losses . 26
5.3 AC filter losses . 26
5.3.1 General . 26
5.3.2 AC filter capacitor losses . 27
5.3.3 AC filter reactor losses . 27
5.3.4 AC filter resistor losses . 28
5.3.5 Total AC filter losses . 28
5.4 Shunt capacitor bank losses . 28
5.5 Shunt reactor losses . 28
5.6 DC smoothing reactor losses . 29
5.7 DC filter losses . 30
5.7.1 General . 30
IEC 61803:2026 © IEC 2026
5.7.2 DC filter capacitor losses . 30
5.7.3 DC filter reactor losses . 31
5.7.4 DC filter resistor losses . 31
5.7.5 Total DC filter losses . 31
5.8 Auxiliaries and station service losses . 31
5.9 Series filter losses . 32
5.10 Phase reactor losses (VSC only) . 33
5.11 Valve reactor losses (VSC only) . 35
5.12 Other equipment losses . 35
Annex A (informative) Calculation of harmonic currents and voltages (LCC only) . 36
A.1 Harmonic currents in converter transformers . 36
A.2 Harmonic currents in the AC filters . 36
A.3 Harmonic voltages on the DC side . 37
A.4 DC side harmonic currents in the smoothing reactor . 37
Annex B (informative) Typical station losses . 38
Annex C (informative) HVDC converter station loss evaluation – An illustration . 39
C.1 General . 39
C.2 Loss evaluation under various cases. 40
Bibliography . 43
Figure 1 – Typical high-voltage direct current (HVDC) equipment for one pole of an
LCC scheme . 10
Figure 2 – Typical high-voltage direct current (HVDC) equipment for one pole of a VSC
scheme . 11
Figure 3 – Simplified three-phase diagram of an HVDC 12-pulse converter (LCC) . 14
Figure 4 – Simplified equivalent circuit of a typical thyristor valve . 15
Figure 5 – Current and voltage waveforms of a valve operating in a 12-pulse converter . 16
Figure 6 – Thyristor on-state characteristic . 17
Figure 7 – Conduction current and voltage drop of thyristor . 18
Figure 8 – Distribution of commutating inductance between L and L . 20
1 2
Figure 9 – Thyristor current during reverse recovery . 22
Figure 10 – Typical phase reactor and valve reactor arrangement per arm of a VSC
scheme . 34
Table B.1 – Typical values of losses for a LCC station . 38
Table B.2 – Typical values of losses for a VSC MMC station . 38
Table C.1 – Conditions for calculation of losses in case D1 . 41
Table C.2 – Conditions for calculation of losses in case D2 . 41
IEC 61803:2026 © IEC 2026
INTERNATIONAL ELECTROTECHNICAL COMMISSION
____________
Determination of power losses in high-voltage
direct current (HVDC) converter stations
FOREWORD
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9) IEC draws attention to the possibility that the implementation of this document may involve the use of (a)
patent(s). IEC takes no position concerning the evidence, validity or applicability of any claimed patent rights in
respect thereof. As of the date of publication of this document, IEC had not received notice of (a) patent(s), which
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the latest information, which may be obtained from the patent database available at https://patents.iec.ch. IEC
shall not be held responsible for identifying any or all such patent rights.
IEC 61803 has been prepared by subcommittee 22F: Power electronics for electrical
transmission and distribution systems, of IEC technical committee 22: Power electronic systems
and equipment. It is an International Standard.
This third edition cancels and replaces the second edition published in 2020. This edition
constitutes a technical revision.
This edition includes the following significant technical changes with respect to the previous
edition:
a) HVDC stations with voltage-sourced converters (VSC) technology have been included;
b) to facilitate the application of this document and to ensure its quality remains consistent,
5.1.8 and 5.8 have been reviewed, taking into consideration that the present thyristor
production technology provides considerably less thyristor parameters dispersion
comparing with the situation in 1999 when the first edition of IEC 61803 was developed;
therefore, the production records of thyristors can be used for the power losses calculation;
IEC 61803:2026 © IEC 2026
c) the calculation of the total station load losses (cases D1 and D2 in Annex C) has been
corrected.
The text of this International Standard is based on the following documents:
Draft Report on voting
22F/860/FDIS 22F/868/RVD
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 International Standard is English.
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/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, or
– revised.
IEC 61803:2026 © IEC 2026
1 Scope
This document applies to all high-voltage direct current (HVDC) converter stations with line-
commutated converters (LCC) as well with voltage-sourced converters (VSC) used for power
exchange (power transmission or back-to-back installation) in utility systems. For line-
commutated converters (LCC), this document presumes the use of 12-pulse thyristor converters
but can, with due care, also be used for 6-pulse thyristor converters.
Where VSC is referred to in this document, it is assumed to be of the MMC-type or similar, with
very low harmonic generation. It is important to treat other types of VSC as appropriate.
In some applications, synchronous compensators, static var compensators (SVC), or static
synchronous compensator (STATCOM) are connected to the AC bus of the HVDC converter
station. The loss determination procedures for such equipment are not included in this
document.
This document presents a set of standard procedures for determining the total losses of an
HVDC converter station, except for VSC valves which are covered by the IEC 62751 series.
The procedures cover all parts, except as noted above, and address no-load operation and
operating losses together with their methods of calculation which use, wherever possible,
measured parameters.
Converter station designs employing novel components or circuit configurations compared to
the typical design assumed in this document, or designs equipped with unusual auxiliary circuits
that can affect the losses, are assessed on their own merits.
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 60076-1, Power transformers - Part 1: General
IEC 60076-6, Power transformers - Part 6: Reactors
IEC 60633, High-voltage direct current (HVDC) transmission - Vocabulary
IEC 60700-1:2015, Thyristor valves for high voltage direct current (HVDC) power transmission -
Part 1: Electrical testing
IEC 60700-1:2015/AMD1:2021
IEC 60871-1, Shunt capacitors for a.c. power systems having a rated voltage above 1 000 V -
Part 1: General
IEC 62747, Terminology for voltage-sourced converters (VSC) for high-voltage direct current
(HVDC) systems
IEC 61803:2026 © IEC 2026
3 Terms, definitions and symbols
For the purposes of this document, the terms and definition given in IEC 60633, IEC 62747 and
the following apply.
ISO and IEC maintain terminological databases for use in standardization at the following
addresses:
– IEC Electropedia: available at http://www.electropedia.org/
– ISO Online browsing platform: available at http://www.iso.org/obp
3.1 Terms and definitions
3.1.1
auxiliary losses
electric power required to feed the converter station auxiliary loads
Note 1 to entry: The auxiliary losses depend on the number of converter units used and whether the station is in
no-load operation or carrying load, in which case the auxiliary losses depend on the load level.
3.1.2
equipment no-load operation losses
losses produced in an item of equipment with the converter station energised but with the
converters blocked and all station service loads and auxiliary equipment connected as required
for immediate pick-up of load to specified minimum power
3.1.3
load level
set of AC system and converter operating conditions at which the converter station is operating
Note 1 to entry: For LCC schemes, the load level is defined by the direct current, direct voltage, firing angle, AC
system voltage and converter transformer tap-changer position.
Note 2 to entry: For VSC schemes, the load level is defined by the direct current, direct voltage, AC system voltage,
interface transformer tap-changer position (where appropriate), converter AC voltage, converter AC current and the
phase angle between converter AC voltage and current.
3.1.4
equipment operating losses
losses produced in an item of equipment at a given load level with the converter station
energised and the converters operating
3.1.5
rated load
load corresponding to operation at nominal values of the operating conditions defined in 3.1.3
Note 1 to entry: The AC system shall be assumed to be at nominal frequency, and its 3-phase voltages are nominal
and balanced. The position of the tap-changer of the converter/interface transformer and the number of AC filters
and shunt reactive elements, if any connected, shall be consistent with operation at rated load, coincident with
nominal conditions.
3.1.6
total station no-load operation losses
sum of all equipment no-load operation losses (3.1.2) and corresponding auxiliary losses (3.1.1)
IEC 61803:2026 © IEC 2026
3.1.7
total station operating losses
sum of all equipment operating losses (3.1.4) and corresponding auxiliary losses (3.1.1) at a
particular load level
Note 1 to entry: An illustrative example using total station operating losses and corresponding loss evaluation is
given in Annex C, case D1.
3.1.8
total station load losses
difference between total station operating losses (3.1.7) and total station no-load operation
losses (3.1.6)
Note 1 to entry: Such calculated total station load losses are considered as being quantitatively equivalent to load
losses as in conventional AC substation practice.
Note 2 to entry: It is recognized that some purchasers evaluate total station no-load operation losses (3.1.6) and
total station load losses individually instead of the evaluating total station operating losses (3.1.7).
Note 3 to entry: An illustrative example to derive load losses, equivalent load losses and corresponding loss
evaluation is given in Annex C, case D2.
3.1.9
station essential auxiliary load
load whose failure affects the conversion capability of the HVDC converter station (e.g. valve
cooling), as well as load that remains working in case of complete loss of AC power supply (e.g.
battery chargers, operating mechanisms)
3.2 Symbols
3.2.1 Common
f AC system frequency, in hertz (Hz)
I direct current, in amperes (A)
d
I harmonic RMS current of order n, in amperes (A)
n
n harmonic order
P power loss in an item of equipment, in watts (W)
Q quality factor of a reactor at harmonic order n
n
R resistance value, in ohms (Ω)
U direct voltage, in volts (V)
d
U harmonic RMS voltage of order n, in volts (V)
n
X inductive reactance at harmonic order n, in ohms (Ω)
n
IEC 61803:2026 © IEC 2026
3.2.2 Line-commutated converters
α (trigger/firing) delay angle, in radians (rad)
γ extinction angle, in radians (rad)
µ overlap angle, in radians (rad)
L inductance, in henrys (H), referred to the valve winding, between the commutating
voltage source and the point of common coupling between star- and delta-connected
windings; L shall include any external inductance between the transformer line-
winding terminals and the point of connection of the AC harmonic filters
L inductance, in henrys (H), referred to the valve winding, between the point of common
coupling between star- and delta-connected windings; the valve L shall include the
saturated inductance of the valve reactors
m electromagnetic notch coupling factor, m = L /(L + L )
1 1 2
N number of series-connected thyristors per valve
t
U RMS value of the phase-to-phase no-load voltage on the valve side of the converter
vo
transformer excluding harmonics, in volts (V)
4 Overview
4.1 General
It is important for suppliers to know in detail how and where losses are generated, since this
affects component and equipment ratings. Purchasers are interested in a verifiable loss figure
which allows equitable bid comparison and in a procedure which can objectively verify the
guaranteed performance requirements of the supplier after delivery. The main purpose of this
document is to serve the purchasers this specific interest.
As a general principle, it would be desirable to determine the efficiency of an HVDC converter
station by a direct measurement of its energy losses. However, attempts to determine the
station losses by subtracting the measured output power from the measured input power should
recognize that such measurements have an inherent inaccuracy, especially if performed at high
voltage. The losses of an HVDC converter station at full load are generally less than 1 % of the
transmitted power. Therefore, the loss measured as a small difference between two large
quantities is not likely to be a sufficiently accurate indication of the actual losses.
In some special circumstances, it can be possible, for example, to arrange a temporary test
connection in which two converters are operated from the same AC source and also connected
together via their DC terminals. In this connection, the power drawn from the AC source equals
the losses in the circuit though in most cases this does not represent a normal operating design
mode. However, the AC source shall also provide var support and commutating voltage to the
two converters. Once again, there are practical measurement difficulties, and it is still important
that the losses are recalculated/corrected for nominal parameters and ambient/operating
conditions.
In order to avoid the problems described above since these practical measurements are
unreliable and also will depend on the type of HVDC solution, it is recommended to use this
document which standardizes a method of calculating the HVDC converter station losses by
summing the losses calculated for each item of equipment. The standardized calculation
method will help the purchaser to meaningfully compare the competing bids. It will also allow
an easy generation of performance curves for the wide range of operating conditions in which
the performance has to be known. In the absence of an inexpensive experimental method which
could be employed for an objective verification of losses during type tests, the calculation
method is the next best alternative as it uses, wherever possible, experimental data obtained
from measurements on individual equipment and components under conditions equivalent to
those encountered in real operation.
IEC 61803:2026 © IEC 2026
Typical high-voltage direct current (HVDC) equipment for one pole of an LCC HVDC substation
is shown in Figure 1 and for one pole of a VSC HVDC substation in Figure 2. The calculation of
harmonic currents and voltages in HVDC equipment for line-commutated converter stations is
described in Annex A.
IEC 61803:2026 © IEC 2026
Key
1 AC switchyard 9 DC smoothing reactor
2 shunt reactor bank 10 voltage divider
3 shunt capacitor bank 11 PLC filter
4 AC filter bank 12 DC filter
5 capacitor voltage transformer 13 DC current measuring device
6 PLC filter 14 pole line
7 converter transformer 15 ground electrode
8 valve hall
Figure 1 – Typical high-voltage direct current (HVDC) equipment
for one pole of an LCC scheme
IEC 61803:2026 © IEC 2026
Key
1 circuit breaker 9 VSC unit
2 pre-Insertion resistor 10 VSC DC capacitor
3 line side harmonic filter 11 DC harmonic filter
4 line side high frequency filter 12 dynamic braking system
5 interface transformer 13 neutral point grounding branch
6 converter side harmonic filter 14 DC reactor
7 + 8 converter side high frequency filter 15 DC cable or overhead transmission line
8 phase reactor
a
In some designs of VSC based on VSC switch type valves, the harmonic filters may not be required.
b
In some designs of VSC, the phase reactor may fulfill part of the function of the converter-side high frequency
filter.
c
In some VSC topologies, each valve of the VSC unit may include a "valve reactor", which can be built into the
valve or provided as a separate component.
d
In some designs of VSC, the VSC DC capacitor may be partly or entirely distributed amongst the three phase
units of the VSC Unit, where it is referred to as the DC submodule capacitors.
e
The philosophy and location of the neutral point grounding branch can be different depending on the design of
the VSC unit.
f
In some designs of VSC, the interface transformer can fulfill part of the function of the line-side high frequency
filter.
g
Optional.
h
Optional, if phase reactors or valve reactors are located on the DC side of the converter.
Figure 2 – Typical high-voltage direct current (HVDC) equipment
for one pole of a VSC scheme
Compared with LCCs, VSCs for HVDC systems generate a much less distorted AC side current
waveform. Depending on the converter topology and the control methods employed for VSC,
the network side voltage generated by the converter can approach a clean fundamental
frequency sinusoid. The VSC converter can be considered as a harmonic voltage source behind
an internal impedance, rather than a current source as for LCCs, as it is the generated harmonic
voltage which remains independent of load. The harmonic levels can be extremely low
compared to LCCs, but due to the adopted switching regime have a significant frequency range
much higher than for LCCs, and can contain inter-harmonics, which are a result of the control
strategy adopted. Refer to the IEC TR 62001-5 for harmonics generation of VSC converters.
NOTE In this document, where the term "harmonic" is used for VSC converters, it is considered to mean the
"harmonic group" according to IEC 61000-4-7, which includes the integer harmonic and the spectral bins from h – 0,5
to h + 0,5, instead of "harmonic number n".
IEC 61803:2026 © IEC 2026
It is important to note that the power loss in each item of equipment will depend on the ambient
conditions under which it operates, as well as on the operating conditions or duty cycles to
which it is subjected. Therefore, the ambient and operating conditions shall be defined for each
item of equipment, based on the ambient and operating conditions of the entire HVDC converter
station.
It is recognized that, for AC and DC side filter equipment, the specified notional requirements
do not represent the actual losses to be expected in service; however, the simplified approach
specified in this document is considered acceptable to estimate losses and compare different
bids.
4.2 Ambient conditions
4.2.1 General
A set of standard reference ambient conditions shall be used for determining the power losses
in HVDC converter stations.
4.2.2 Outdoor standard reference temperature
An outdoor ambient dry bulb temperature of 20 °C shall be used as the standard reference
temperature for determining the total converter station losses. The corresponding valve hall
temperature can be defined by the supplier if necessary. The equivalent wet-bulb temperature
(where necessary) shall be defined by the purchaser.
If not defined, the wet-bulb temperature is recommended to be 14 °C, which corresponds to
approximately 50 % RH at 20 °C dry bulb temperature.
4.2.3 Coolant standard reference temperature
Where forced cooling is used for equipment, the flow rate and temperature of the coolant can
influence the temperature rise and associated losses of that equipment. Therefore, the coolant
temperatures and flow rates established by the purchaser and the supplier shall be used as a
basis for determining the losses.
4.2.4 Standard reference air pressure
The reference air pressure to be used for the evaluation of total converter station power losses
shall be the standard atmospheric pressure (101,3 kPa) corrected to the altitude of the
installation in question when station is located above 1 000 m above sea level.
4.3 Operating parameters
The losses of an HVDC converter station depend on its operating parameters.
The losses of HVDC converter stations are classified into two categories, referred to as
operating losses (3.1.4 and 3.1.7) and no-load operation losses (3.1.2 and 3.1.6).
The operating losses and auxiliary losses are affected by the load level of the station because
the numbers of certain types of energised equipment (for example harmonic filters and cooling
equipment) can depend upon the load level and because losses in individual items of equipment
themselves vary with the load level.
HVDC converter station losses shall be determined for nominal (balanced) AC system voltage
and frequency, symmetrical impedances of the transformer (between phases, and for LCC
schemes, between the star and delta-connected bridges) and, for LCC schemes, symmetrical
firing angles. The transformer tap-changer shall be assumed to be in the position corresponding
to nominal AC system voltage or as decided by the control system for the defined operating
condition.
IEC 61803:2026 © IEC 2026
The operating losses shall be determined for the load levels specified by the purchaser, or at
rated load if no such conditions are specified. For each load level, the converter operating
conditions defined in 3.1.3, shunt compensation and harmonic filtering equipment shall be
consistent with the respective load level and other specified performance requirements,
relating, for example, to harmonic distortion and minimum reactive power exchange with the
connected ac network. Cooling and other auxiliary equipment, as appropriate to the standard
reference temperature (see 4.2.2 and 4.2.3), shall be assumed to be connected to support the
respective load level. Unless specifically specified, reactive power shall be assumed zero for a
VSC station.
For the no-load operation mode, transformers shall be energised and the converters blocked.
All filters and reactive power compensation equipment shall be assumed to be disconnected
except for those which are required to sustain operation at zero load in order, for example, to
meet the specified reactive power requirements. Station service loads and auxiliary equipment
(e.g. cooling-water pumps) shall be assumed to be connected as required for immediate pick-
up of load for the converter station (without waiting for tap changer movement) to specified
minimum power.
NOTE For some MMC VSC valves, it can be impracticable to keep the converter blocked with AC circuit breaker
closed for a while, due to a need for balancing the submodule capacitor voltages. The operating state generally
known as "idling operating state" will also have an additional contribution of valve losses. However, for the purpose
of guaranteeing loss calculation, it is sufficient to compare losses for no-load operation losses as defined in 3.1.2 at
zero active and reactive power.
5 Determination of equipment losses
5.1 Thyristor valve losses (LCC only)
5.1.1 General
The loss production mechanisms applicable when the valves are blocked (no-load operation
losses) are different from those applicable in normal operation (operating losses). Operating
losses are dealt with in 5.1.2 to 5.1.11, and no-load operation losses are dealt with in 5.1.12.
Auxiliary losses are dealt with in 5.8.
A simplified three-phase diagram of an HVDC 12-pulse converter is shown in Figure 3.
Individual valves are marked in the order of their conduction sequence.
IEC 61803:2026 © IEC 2026
Key
A high-voltage DC terminal
B upper bridge
C lower bridge
D low voltage DC terminal
Figure 3 – Simplified three-phase diagram of an HVDC 12-pulse converter (LCC)
A simplified equivalent circuit of a typical valve is shown in Figure 4, where symbol "th"
combines the effects of N thyristors connected in series in the valve. C and R are the
t AC AC
corresponding combined values of R-C damping circuits used for voltage sharing and
overvoltage suppression. R represents DC grading resistors and other resistive components
DC
which incur loss when the valve blocks voltage; it also includes the effects of the thyristor
leakage current (see 5.1.5 and 5.1.12). C includes both stray capacitances and surge
s
distribution capacitors (if used). L represents saturable reactors used to limit the di/dt stresses
s
to safe values and to improve the distribution of fast rising voltages. R represents the
s
resistances of the current conducting components of the valve such as the busbars, contact
resistances, resistance of the windings of the saturable reactors, etc. Power losses in the valve
surge arrester (not shown) shall be neglected.
IEC 61803:2026 © IEC 2026
Key
1 control and monitoring
Figure 4 – Simplified equivalent circuit of a typical thyristor valve
Figure 5 shows, as an example, current and voltage waveforms of valve 1 (according to Figure 3)
operating in rectifier – Figure 5 a) – and inverter – Figure 5 b) – modes. In the example shown,
the firing instants of the valves of the upper bridge are delayed by 30° with respect to the valves
of the lower bridge due to the phase shift between the two secondaries. For each valve, the
length of the conduction intervals is about 130° (2π/3 + μ). During commutations, the valve
current is assumed, for this document, to be changing linearly whereas, in reality, the valve
currents follow portions of sine waves. This simplification has negligible effect on the resulting
losses, while the trapezoidal waveform significantly simplifies the calculations. The voltage
blocked by the valve shows notches caused by commutations between individual valves.
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