SIST EN IEC 61803:2021

SLOVENSKI STANDARD
01-februar-2021
Nadomešča:
SIST EN 61803:2001
SIST EN 61803:2001/A1:2011
SIST EN 61803:2001/A2:2016
Ugotavljanje močnostnih izgub v visokonapetostnih enosmernih (HVDC)
pretvorniških postajah s pretvorniki s komutiranjem (IEC 61803:2020)
Determination of power losses in high-voltage direct current (HVDC) converter stations
with line-commutated converters (IEC 61803:2020)
Bestimmung der Leistungsverluste in Hochspannungsgleichstrom-
(HGÜ-)Stromrichterstationen mit netzgeführten Stromrichtern (IEC 61803:2020)
Détermination des pertes en puissance dans les postes de conversion en courant
continu à haute tension (CCHT) munis de convertisseurs commutés par la ligne (IEC
61803:2020)
Ta slovenski standard je istoveten z: EN IEC 61803:2020
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
December 2020
ICS 29.200 Supersedes EN 61803:1999 and all of its amendments
and corrigenda (if any)
English Version
Determination of power losses in high-voltage direct current
(HVDC) converter stations with line-commutated converters
(IEC 61803:2020)
Détermination des pertes en puissance dans les postes de Bestimmung der Leistungsverluste in
conversion en courant continu à haute tension (CCHT) Hochspannungsgleichstrom- (HGÜ-)Stromrichterstationen
munis de convertisseurs commutés par la ligne mit netzgeführten Stromrichtern
(IEC 61803:2020) (IEC 61803:2020)
This European Standard was approved by CENELEC on 2020-11-23. 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,
Turkey 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
© 2020 CENELEC All rights of exploitation in any form and by any means reserved worldwide for CENELEC Members.
Ref. No. EN IEC 61803:2020 E
European foreword
The text of document 22F/563/CDV, future edition 2 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 61803:2020.
The following dates are fixed:
• latest date by which the document has to be implemented at national (dop) 2021-08-23
level by publication of an identical national standard or by endorsement
• latest date by which the national standards conflicting with the (dow) 2023-11-23
document have to be withdrawn
This document supersedes EN 61803:1999 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.
Endorsement notice
The text of the International Standard IEC 61803:2020 was approved by CENELEC as a European
Standard without any modification.
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.cenelec.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
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 61803 ®
Edition 2.0 2020-10
INTERNATIONAL
STANDARD
NORME
INTERNATIONALE
Determination of power losses in high-voltage direct current (HVDC) converter

stations with line-commutated converters

Détermination des pertes en puissance dans les postes de conversion

en courant continu à haute tension (CCHT) munis de convertisseurs commutés

par la ligne
INTERNATIONAL
ELECTROTECHNICAL
COMMISSION
COMMISSION
ELECTROTECHNIQUE
INTERNATIONALE
ICS 29.200 ISBN 978-2-8322-8948-8

– 2 – IEC 61803:2020 © IEC 2020
CONTENTS
FOREWORD . 4
1 Scope . 6
2 Normative references . 6
3 Terms, definitions and symbols. 6
3.1 Terms and definitions . 7
3.2 Symbols . 8
4 Overview . 8
4.1 General . 8
4.2 Ambient conditions. 9
4.2.1 General . 9
4.2.2 Outdoor standard reference temperature . 9
4.2.3 Coolant standard reference temperature . 9
4.2.4 Standard reference air pressure . 10
4.3 Operating parameters . 10
5 Determination of equipment losses . 10
5.1 Thyristor valve losses . 10
5.1.1 General . 10
5.1.2 Thyristor conduction loss per valve . 11
5.1.3 Thyristor spreading loss per valve . 12
5.1.4 Other conduction losses per valve . 12
5.1.5 DC voltage-dependent loss per valve . 13
5.1.6 Damping loss per valve (resistor-dependent term) . 14
5.1.7 Damping loss per valve (change of capacitor energy term) . 14
5.1.8 Turn-off losses per valve . 15
5.1.9 Reactor loss per valve . 15
5.1.10 Total valve losses . 16
5.1.11 Temperature effects. 16
5.1.12 No-load operation loss per valve . 16
5.2 Converter transformer losses . 17
5.2.1 General . 17
5.2.2 No-load operation losses . 17
5.2.3 Operating losses. 17
5.2.4 Auxiliary power losses . 18
5.3 AC filter losses . 19
5.3.1 General . 19
5.3.2 AC filter capacitor losses . 19
5.3.3 AC filter reactor losses . 19
5.3.4 AC filter resistor losses . 20
5.3.5 Total AC filter losses . 20
5.4 Shunt capacitor bank losses . 20
5.5 Shunt reactor losses . 20
5.6 DC smoothing reactor losses . 21
5.7 DC filter losses . 21
5.7.1 General . 21
5.7.2 DC filter capacitor losses . 22
5.7.3 DC filter reactor losses . 22

IEC 61803:2020 © IEC 2020 – 3 –
5.7.4 DC filter resistor losses . 23
5.7.5 Total DC filter losses . 23
5.8 Auxiliaries and station service losses . 23
5.9 Series filter losses . 24
5.10 Other equipment losses . 25
Annex A (informative) Calculation of harmonic currents and voltages . 31
A.1 Harmonic currents in converter transformers . 31
A.2 Harmonic currents in the AC filters . 31
A.3 Harmonic voltages on the DC side . 32
A.4 DC side harmonic currents in the smoothing reactor . 32
Annex B (informative) Typical station losses . 33
Annex C (informative) HVDC converter station loss evaluation – An illustration . 34
C.1 General . 34
C.2 Loss evaluation under various cases . 35
Bibliography . 37

Figure 1 – Typical high-voltage direct current (HVDC) equipment for one pole . 26
Figure 2 – Simplified three-phase diagram of an HVDC 12-pulse converter . 27
Figure 3 – Simplified equivalent circuit of a typical thyristor valve . 27
Figure 4 – Current and voltage waveforms of a valve operating in a 12-pulse converter . 28
Figure 5 – Thyristor on-state characteristic . 29
Figure 6 – Conduction current and voltage drop . 29
Figure 7 – Distribution of commutating inductance between L and L . 30
1 2
Figure 8 – Thyristor current during reverse recovery . 30

Table B.1 – Typical values of losses . 33
Table C.1 – Conditions for calculation of losses in case D1 . 36
Table C.2 – Conditions for calculation of losses in Case D2. . 36

– 4 – IEC 61803:2020 © IEC 2020
INTERNATIONAL ELECTROTECHNICAL COMMISSION
____________
DETERMINATION OF POWER LOSSES IN HIGH-VOLTAGE
DIRECT CURRENT (HVDC) CONVERTER STATIONS WITH
LINE-COMMUTATED CONVERTERS
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.
International Standard 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.
This second edition cancels and replaces the first edition published in 1999,
Amendment 1:2010 and Amendment 2:2016. This edition constitutes a technical revision.
This edition includes the following significant technical changes with respect to the previous
edition:
a) 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,
and therefore the production records of thyristors can be used for the power losses
calculation;
IEC 61803:2020 © IEC 2020 – 5 –
b) 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:
CDV Report on voting
22F/563/CDV 22F/580A/RVC
Full information on the voting for the approval of this International Standard can be found in
the report on voting indicated in the above table.
This document has been drafted in accordance with the ISO/IEC Directives, Part 2.
The committee has decided that the contents of this document will remain unchanged until the
stability date indicated on the IEC website under "http://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.
– 6 – IEC 61803:2020 © IEC 2020
DETERMINATION OF POWER LOSSES IN HIGH-VOLTAGE
DIRECT CURRENT (HVDC) CONVERTER STATIONS WITH
LINE-COMMUTATED CONVERTERS
1 Scope
This document applies to all line-commutated high-voltage direct current (HVDC) converter
stations used for power exchange (power transmission or back-to-back installation) in utility
systems. This document presumes the use of 12-pulse thyristor converters but can, with due
care, also be used for 6-pulse thyristor converters.
In some applications, synchronous compensators or static var compensators (SVC) may be
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. 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 could 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 60871-1, Shunt capacitors for a.c. power systems having a rated voltage above 1 000 V –
Part 1: General
3 Terms, definitions and symbols
For the purposes of this document, the terms and definition given in IEC 60633 and the
following apply.
IEC 61803:2020 © IEC 2020 – 7 –
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
direct current, direct voltage, firing angle, AC voltage, and converter transformer tap-changer
position at which the converter station is operating
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 related to operation at nominal values of DC current, DC voltage, AC voltage and
converter firing angle
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 transformer and the number of AC filters
and shunt reactive elements 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)
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.

– 8 – IEC 61803:2020 © IEC 2020
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 will affect the conversion capability of the HVDC converter station (e.g.
valve cooling), as well as load that shall remain working in case of complete loss of AC power
supply (e.g. battery chargers, operating mechanisms)
3.2 Symbols
α (trigger/firing) delay angle, in radians (rad)
overlap angle, in radians (rad)
µ
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
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, and 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 harmonic order
N number of series-connected thyristors per valve
t
P power loss in an item of equipment, in watts (W)
Q
quality factor 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
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)
X
inductive reactance at harmonic order n, in ohms (Ω)
n
4 Overview
4.1 General
Suppliers need 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 after delivery which can objectively verify
the guaranteed performance requirements of the supplier.

IEC 61803:2020 © IEC 2020 – 9 –
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 may 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. However, the AC source shall also provide var support
and commutating voltage to the two converters. Once again, there are practical measurement
difficulties.
In order to avoid the problems described above, this document 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.
The calculation of harmonic currents and voltages in HVDC equipment is described in
Annex A.
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.
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. Corresponding valve hall
temperature may 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.

– 10 – IEC 61803:2020 © IEC 2020
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.
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) may 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 converter transformer and 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.
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 valve-winding AC
voltage, DC current, converter firing angle, 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 reactive power. 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.
For the no-load operation mode, converter 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.
5 Determination of equipment losses
5.1 Thyristor valve losses
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.
Typical high-voltage direct current (HVDC) equipment for one pole of a HVDC substation is
shown in Figure 1.
A simplified three-phase diagram of an HVDC 12-pulse converter is shown in Figure 2.
Individual valves are marked in the order of their conduction sequence.

IEC 61803:2020 © IEC 2020 – 11 –
A simplified equivalent circuit of a typical valve is shown in Figure 3. Symbol "th" combines
together 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
DC
components which incur loss when the valve blocks voltage. It also includes the effects of the
includes both stray capacitances and
thyristor leakage current (see 5.1.5 and 5.1.12). C
s
surge distribution capacitors (if used). L represents saturable reactors used to limit the di/dt
s
stresses to safe values and to improve the distribution of fast rising voltages. R represents
s
the 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.
Figure 4 shows, as an example, current and voltage waveforms of valve 1 (according to Figure 2)
operating in rectifier – Figure 4 a) – and inverter – Figure 4 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 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.
5.1.2 Thyristor conduction loss per valve
A typical thyristor on-state characteristic is shown in Figure 5. Thyristor conduction loss
component is the product of the conduction current i(t) – Figure 6 a) – and the corresponding
ideal on-state voltage as shown in Figure 5. Formula P shall be used provided that the DC
V1a
bridge current is well smoothed. In the event that the root sum square value of the DC side
harmonic currents, determined in accordance with Clause A.4, exceeds 5 % of the DC
component, formula P shall be used instead.
V1b
NI×  2π− µ 

td
P U+ RI××
V1a 0 0 d 

32π


n=48

N ××I U N × R 2π − µ

td 0 t 0

P= ++II
V1b d n
∑ 

33 2π

n=12

where
is the current-independent component of the on-state voltage of the average thyristor
U
(see note below), in volts;
R is the slope resistance of the on-state characteristic of the average thyristor (see note
below), in ohms;
th
is the calculated RMS value of the n harmonic current in the bridge DC connection
I
n
according to Clause A.4, in amperes.
NOTE U and R (see Figure 5) are determined from the fully spread on-state voltage measured at the
0 0
appropriate current and junction temperature. The average value of U and R is obtained from production records
0 0
of the thyristors. The temperature dependence of U and R is established from type tests or routine tests on a
0 0
statistically significant number of the thyristors employed, and is used, where necessary, to correct U and R to
0 0
the appropriate service junction temperature. If parallel connection of p thyristors is employed, the appropriate
100 % current is the nominal DC bridge current divided by p. The calculated result is then multiplied by p.
=
– 12 – IEC 61803:2020 © IEC 2020
5.1.3 Thyristor spreading loss per valve
This loss component is an additional conduction loss of the thyristors arising from the delay in
establishing full conduction of the silicon after the thyristor has been turned on. The additional
loss is the product of the current and the voltage by which the thyristor voltage exceeds the
ideal thyristor on-state voltage drop – see the hatched area in Figure 6 b).
t1
P = N××f u t− u t ×i t dt
( ) ( ) ( )
V2 t B A

∫
where
t is the length of the conduction interval, in seconds, which is given by:
π + µ
;
t =
2πf
(t) is the instantaneous on-state voltage, in volts, of a thyristor whose fully spread on-
u
B
state voltage is typical for the thyristors used; the instantaneous on-state voltage shall
be determined for the appropriate junction temperature measured with a trapezoidal
current pulse exhibiting the correct amplitude and commutation overlap periods (see
Figure 5 and Figure 6);
u (t) is the calculated instantaneous on-state voltage of the average thyristor at the same
A
junction temperature for the same current pulse but with the conducting area fully
established throughout the conduction, as derived from its on-state characteristic
represented by U and R only (see Figure 6);
0 0
i(t) is the instantaneous current in the thyristor, in amperes.
Instantaneous on-state voltage data, including the effects of spreading, are usually not
available from production records. Measurements of typical thyristor on-state voltage,
including spreading, should therefore be obtained during the valve periodic firing and
extinction type test (IEC 60700-1:2015, Clause 9) or, alternatively, from a separate laboratory
test on a statistically significant number of thyristors.
5.1.4 Other conduction losses per valve
These are the conduction losses in the main circuit of the valve due to components other than
the thyristors.
R ⋅ I 2π − µ

sd
P =
V3 
32π

where
R is the DC resistance of the valve terminal-to-terminal circuit excluding the thyristors, in
s
ohms (see Figure 3).
The value of R is determined by direct measurement on a representative valve section that
s
includes all elements of the main circuit of a valve in the correct proportions, but in which the
thyristors have been replaced by copper blocks of the appropriate dimensions and with
contacts treated in the same way as for real thyristors. Alternatively, the resistance may be
calculated, in which case the calculation methods shall be documented.

IEC 61803:2020 © IEC 2020 – 13 –
5.1.5 DC voltage-dependent loss per valve
This loss component is the loss in the shunt resistance R of the valve (see Figure 3),
DC
arising from the voltage which appears between valve terminals during the non-conducting
interval (see Figure 4). It includes losses due to thyristor off-state and reverse leakage, losses
in DC grading resistors, other resistive circuits and elements connected in parallel with the
thyristors, resistance of the coolant in coolant pipes, resistivity effects of the structure, fibre
optics, etc.
2 2

U
4 3 6mm−−12 7
v0
P π+ cos 2α+cos 2αµ+2 + sin 2α−sin 2αµ+2+2µ
( ) ( ) ( ) ( )

v4
   
2  π R 3 4 8
DC


where
R is the effective off-state DC resistance of a complete valve determined by measuring
DC
the current drawn during the valve terminal-to-terminal DC voltage type test (according
to IEC 60700-1:2015, 8.3.1) in ohms; if a type test is not performed on the thyristor
valve, R shall be determined by reference to a previous type test (see also the
DC
paragraph after Note 1 below);
m = L /(L + L );
1 1 2
L is the inductance, in henrys, 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 (see Figure 7);
L is the inductance, in henrys, referred to the valve winding, between the point of
common coupling between star- and delta-connected windings, and the valve; L shall
include the saturated inductance of the valve reactors (see Figure 7).
The value of L shall be the same for both secondaries (L = L ) (see Note 2 and last
2 2Δ 2Y
paragraph below).
NOTE 1 The formula for P is valid for µ < π/6 (30°) only.
V4
Since the thyristor resistive leakage current is usually much higher at operating temperatures
than at the prevailing ambient air temperature, it is either necessary to heat the thyristors of
the valve to the correct operating temperature before the measurement of R is taken or to
DC
make later corrections to the measured value using the average thyristor data obtained
separately, to include the mentioned temperature effect (see also 5.1.11). The same pertains
to the liquid coolant.
NOTE 2 The value of m quantifies the effects of inductive coupling between the two secondaries of the converter
transformer. It determines the magnitude of the notches caused by the commutation in the other bridge (notches
from 1' to 3' and from 4' to 6' in Figure 4). If m = 0, then there is no coupling between the two bridges and the
notches from 1' to 3' and from 4' to 6' disappear altogether. The notches in Figure 4 correspond to m = 0,2.
Values of L and L are obtained from the short-circuit impedance measurements on the
1 2
converter transformers, and by adding any external inductances as required. The value of L
includes any external common inductance (such as power line carrier filters) between the
point of common coupling and the commutation voltage source. In cases where no AC
harmonic filters are connected, L also
...