IEC 61803:1999

IEC 61803 ®
Edition 1.2 2016-05
CONSOLIDATED VERSION
INTERNATIONAL
STANDARD
NORME
INTERNATIONALE
colour
inside
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
le réseau
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IEC 61803 ®
Edition 1.2 2016-05
CONSOLIDATED VERSION
INTERNATIONAL
STANDARD
NORME
INTERNATIONALE
colour
inside
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

le réseau
INTERNATIONAL
ELECTROTECHNICAL
COMMISSION
COMMISSION
ELECTROTECHNIQUE
INTERNATIONALE
ICS 29.200 ISBN 978-2-8322-3438-9

IEC 61803 ®
Edition 1.2 2016-05
CONSOLIDATED VERSION
REDLINE VERSION
VERSION REDLINE
colour
inside
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
le réseau
– 2 – IEC 61803:1999+AMD1:2010
+AMD2:2016 CSV © IEC 2016
CONTENTS
FOREWORD. 4
1 Scope . 6
2 Normative references . 6
3 Definitions and symbols . 6
3.1 Definitions . 7
3.2 Letter symbols . 7
4 General . 8
4.1 Introduction . 8
4.2 Ambient conditions . 9
4.2.1 Outdoor standard reference temperature . 9
4.2.2 Coolant standard reference temperature . 9
4.2.3 Standard reference air pressure . 9
4.3 Operating parameters . 9
5 Determination of equipment losses . 10
5.1 Thyristor valve losses . 10
5.1.1 Thyristor conduction loss per valve . 10
5.1.2 Thyristor spreading loss per valve . 11
5.1.3 Other conduction losses per valve . 11
5.1.4 D.C. voltage-dependent loss per valve . 12
5.1.5 Damping loss per valve (resistor-dependent term) . 13
5.1.6 Damping loss per valve (change of capacitor energy term) . 13
5.1.7 Turn-off losses per valve . 14
5.1.8 Reactor loss per valve . 14
5.1.9 Total valve losses . 15
5.1.10 Temperature effects . 15
5.1.11 No-load operation loss per valve . 15
5.2 Converter transformer losses . 16
5.2.1 General . 16
5.2.2 No-load operation losses . 16
5.2.3 Operating losses . 16
5.2.4 Auxiliary power losses . 17
5.3 AC filter losses . 17
5.3.1 General . 17
5.3.2 AC filter capacitor losses . 18
5.3.3 AC filter reactor losses . 18
5.3.4 AC filter resistor losses . 18
5.3.5 Total a.c. filter losses . 18
5.4 Shunt capacitor bank losses . 18
5.5 Shunt reactor losses . 19
5.6 DC smoothing reactor losses . 19
5.7 DC filter losses . 20
5.7.1 General . 20
5.7.2 DC filter capacitor losses . 20
5.7.3 DC filter reactor losses . 20
5.7.4 DC filter resistor losses . 21
5.7.5 Total d.c. filter losses . 21

+AMD2:2016 CSV © IEC 2016
5.8 Auxiliaries and station service losses . 21
5.9 Radio interference/PLC Series filter losses . 22
5.10 Other equipment losses . 23
Annex A (normative)  Calculation of harmonic currents and voltages . 29
A.1 Harmonic currents in converter transformers . 29
A.2 Harmonic currents in the a.c. filters . 29
A.3 Harmonic voltages on the d.c. side . 30
A.4 DC side harmonic currents in the smoothing reactor . 30
Annex B (informative)  Typical station losses . 31
Annex C (informative)  Bibliography . 35
Annex D (informative) HVDC converter station loss evaluation – An illustration . 32

Figure 1 – Typical high-voltage direct current (HVDC) equipment for one pole (auxiliary
equipment is not shown) . 24
Figure 2 – Simplified three-phase diagram of an HVDC 12-pulse converter . 25
Figure 3 – Simplified equivalent circuit of a typical thyristor valve . 25
Figure 4a – Rectifier operation . 26
Figure 4b – Inverter operation . 26
Figure 4 – Current and voltage waveforms of a valve operating in a 12-pulse converter
(commutation overshoots are not shown) . 26
Figure 5 – Thyristor on-state characteristic . 27
Figure 6a – Conduction current . 27
Figure 6b – Voltage drop across an ideal thyristor A or a real thyristor B . 27
Figure 6 – Conduction current and voltage drop . 27
Figure 7 – Distribution of commutating inductance between L and L . 28
1 2
Figure 8 – Thyristor current during reverse recovery . 28

Table D.1 — Conditions for calculation of losses in Case D . 34

– 4 – IEC 61803:1999+AMD1:2010
+AMD2:2016 CSV © IEC 2016
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,
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Publication(s)”). Their preparation is entrusted to technical committees; any IEC National Committee interested
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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
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between any IEC Publication and the corresponding national or regional publication shall be clearly indicated in
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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.
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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.
This consolidated version of the official IEC Standard and its amendments has been prepared
for user convenience.
IEC 61803 edition 1.2 contains the first edition (1999-02) [documents 22F/51/FDIS and 22F/56/
RVD] and its corrigendum 1 (1999-10), its amendment 1 (2010-11) [documents 22F/214/CDV and
22F/224/RVC] and its amendment 2 (2016-05) [documents 22F/374/CDV and 22F/393A/RVC].
In this Redline version, a vertical line in the margin shows where the technical content is
modified by amendments 1 and 2. Additions are in green text, deletions are in strikethrough
red text. A separate Final version with all changes accepted is available in this publication.

+AMD2:2016 CSV © IEC 2016
International Standard IEC 61803 has been prepared by subcommittee 22F: Power
electronics for electrical transmission and distribution systems, of IEC technical committee 22:
Power electronics.
Annex A forms an integral part of this standard.
Annexes B and C are for information only.
The committee has decided that the contents of the base publication and its amendments will
remain unchanged until the stability date indicated on the IEC web site under
"http://webstore.iec.ch" in the data related to the specific publication. At this date, the
publication will be
• reconfirmed,
• withdrawn,
• replaced by a revised edition, or
• amended.
IMPORTANT – The 'colour inside' logo on the cover page of this publication indicates
that it contains colours which are considered to be useful for the correct
understanding of its contents. Users should therefore print this document using a
colour printer.
– 6 – IEC 61803:1999+AMD1:2010
+AMD2:2016 CSV © IEC 2016
DETERMINATION OF POWER LOSSES IN HIGH-VOLTAGE
DIRECT CURRENT (HVDC) CONVERTER STATIONS WITH LINE-
COMMUTATED CONVERTERS
1 Scope
This International Standard applies to all line-commutated high-voltage direct current (HVDC)
converter stations used for power exchange in utility systems. This standard 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 a.c. bus of the HVDC converter station. The loss determination procedures
for such equipment are not included in this standard.
This standard presents a set of standard procedures for determining the total losses of an
HVDC converter station. Typical HVDC equipment is shown in figure 1. 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 standard, or designs equipped with unusual auxiliary
circuits that could affect the losses, shall be assessed on their own merits.
2 Normative references
The following referenced documents are indispensable for the application 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 60076-1:1993, Power transformers – Part 1: General
IEC 60076-6, Power transformers – Part 6: Reactors
IEC 60289:1988, Reactors
IEC 60633:1998, Terminology for high-voltage direct current (HVDC) transmission
IEC 60700-1:1998, Thyristor valves for high voltage direct current (HVDC) power transmission –
Part 1: Electrical testing
IEC 60747-6:1983, Semiconductor devices – Discrete devices – Part 6: Thyristors
IEC 60871-1:1997, Shunt capacitors for a.c. power systems having a rated voltage above
1 000 V – Part 1: General performance, testing and rating – Safety requirements – Guide for
installation and operation
3 Definitions and symbols
For the purpose of this International Standard, the following definitions apply:

+AMD2:2016 CSV © IEC 2016
3.1 Definitions
3.1.1
auxiliary losses
the 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
the 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
this term specifies the direct current, direct voltage, firing angle, a.c. voltage, and converter
transformer tap-changer position at which the converter station is operating
3.1.4
equipment operating losses
the losses produced in an item of equipment at a given load level with the converter station
energized and the converters operating
3.1.5
rated load
this load is related to operation at nominal values of d.c. current, d.c. voltage, a.c. voltage and
converter firing angle
Note 1 to entry: The a.c. 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 a.c. filters
and shunt reactive elements connected shall be consistent with operation at rated load, coincident with nominal
conditions.
3.1.8
total station no-load operation losses
sum of all equipment no-load operation losses (3.1.2) and corresponding auxiliary losses
(3.1.1)
3.1.6
total station operating losses
the total station loss is the sum of all equipment operating or no-load operation losses (3.1.4)
and the corresponding auxiliary losses (3.1.1) at a particular load level
Note 1 to entry: It is recognised that some purchasers evaluate “total station no-load operation losses” (definition
3.1.8) and total station load losses individually instead of the evaluating “total station operating losses” (definition
3.1.6).
Note 2 to entry: "Operating losses” minus “no-load operation losses” may be considered as being quantitatively
equivalent to “load losses” as in conventional a.c. substation practice.
Note 3 to entry: An illustrative example to derive “load losses”, “equivalent load losses” and corresponding “loss
evaluation” is given in Annex D.
3.1.7
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 must remain working in case of complete loss of a.c.
power supply (e.g. battery chargers, operating mechanisms)
3.2 Letter symbols
α (trigger/firing) delay angle, in radians (rad)

– 8 – IEC 61803:1999+AMD1:2010
+AMD2:2016 CSV © IEC 2016
µ commutation overlap angle, in radians (rad)
f a.c. system frequency, in hertz (Hz)
I direct current, in the bridge d.c. connection, in amperes (A)
d
I harmonic r.m.s. current of order n, in amperes (A)
n
L the 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 a.c. harmonic filters
L the 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 the 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 (W) (Ω)
U direct voltage, in volts (V)
d
U harmonic r.m.s. voltage of order n, in volts (V)
n
U r.m.s. 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 General
4.1 Introduction
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.
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 a.c. source and also
connected together via their d.c. terminals. In this connection, the power drawn from the a.c.
source equals the losses in the circuit. However, the a.c. source must 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 standard 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

+AMD2:2016 CSV © IEC 2016
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.
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
A set of standard reference ambient conditions shall be used for determining the power losses
in HVDC converter stations.
4.2.1 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.
NOTE 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.
4.2.2 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.
4.2.3 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 three two categories, termed the no-
load operation losses, operating losses and auxiliary losses referred to as operating losses
(3.1.4 and 3.1.6) and no-load operation losses (3.1.2 and 3.1.8).
The operating losses and auxiliary losses are affected by the load level of the station because
the numbers of certain types of energized 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) a.c. 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 a.c. system voltage or as decided by the control system for the
defined operating condition.
– 10 – IEC 61803:1999+AMD1:2010
+AMD2:2016 CSV © IEC 2016
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 a.c.
voltage, d.c. 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 4.2.1
and 4.2.2), shall be assumed to be connected to support the respective load level.
For the no-load operation mode, converter transformers shall be energized 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
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 subclauses 5.1.1 to 5.1.10, and no-load operation losses are dealt
with in 5.1.11. Auxiliary losses are dealt with in 5.8.
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.
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 d.c. grading resistors and other resistive
DC
components which incur loss when the valve blocks voltage. It also includes the effects of the
thyristor leakage current (see 5.1.4 and 5.1.11). C includes both stray capacitances and
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 and inverter 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 standard, 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.
5.1.1 Thyristor conduction loss per valve
This loss component is the product of the conduction current i(t) and the corresponding ideal
on-state voltage as shown in figures 5 and 6. Formula P shall be used provided that the
V1a
d.c. bridge current is well smoothed. In the event that the root sum square value of the d.c.
side harmonic currents, determined in accordance with clause A.4 (annex A), exceeds 5 % of
the d.c. component, formula P shall be used instead.
V1b
+AMD2:2016 CSV © IEC 2016
N ×I  2π − µ 
 
t d
P = U + R ×I ×  
V1a  0 0 d 
3 2π
 
 
n=48
 
N ×I ×U N ×R 2π − µ
 
t d 0 t 0 2 2
 
P = + I + I  
V1b n
d ∑
 
3 3 2π
 
 n=12 
where
U is the current-independent component of the on-state voltage of the average thyristor
(see note below), in volts;
R is the slope resistance of the on-state characteristic of the average thyristor (see note
below), in ohms;
I is the calculated r.m.s. value of the nth harmonic current in the bridge d.c. connection
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 appropriate
0 0
current and junction temperature. The average value of U and R is obtained from production records of the
0 0
thyristors manufactured for the specific project at 100 % and 50 % of nominal d.c. current. The temperature
dependence of U and R is established from type tests or routine tests on a statistically significant number of the
0 0
thyristors employed, and is used, where necessary, to correct U and R to the appropriate service junction
0 0
temperature. If parallel connection of p thyristors is employed, the appropriate 100 % current is the nominal d.c.
bridge current divided by p. The calculated result is then multiplied by p.
5.1.2 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).
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
u (t) is the instantaneous on-state voltage, in volts, of a thyristor whose fully spread on-state
B
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 figures 5
and 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.
NOTE 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 (see IEC 60700-1) or, alternatively, from a
separate laboratory test on a statistically significant number of thyristors.
5.1.3 Other conduction losses per valve
These are the conduction losses in the main circuit of the valve due to components other than
the thyristors.
– 12 – IEC 61803:1999+AMD1:2010
+AMD2:2016 CSV © IEC 2016
R ⋅I
2π − µ
s  
d
P =  
V3
3 2π
 
where
R is the d.c. 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.
5.1.4 D.C. voltage-dependent loss per valve
This loss component is the loss in the shunt resistance R of the valve (see figure 3), arising
DC
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 d.c.
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.
 
U
 4 3 6m − 12m − 7 
v0
P = π + [cos(2α ) + cos(2α + 2µ)] + [sin(2α ) − sin(2α + 2µ) + 2µ]
V4  
2π  R 3 4 8
 
DC
 
 
U
 4 3 6m − 12m− 7 
v0
P = π + [cos (2α ) + cos (2α + 2µ)]+ [sin (2α ) − sin (2α + 2µ) + 2µ]
v4  
2π  R 3 4 8
 
DC
 
where
R is the effective off-state d.c. resistance of a complete valve determined by measuring
DC
the current drawn during the valve terminal-to-terminal d.c. voltage type test (see IEC
60700) in ohms. If a type test is not performed on the thyristor valve, R shall be
DC
determined by reference to a previous type test (see also note 2 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 a.c. 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 notes 3 and 4 below).
2 2d 2y
NOTE 1 The equation for P is valid for µ < π/6 (30°) only.
V4
NOTE 2 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 make later corrections to the measured value using the
DC
average thyristor data obtained separately, to include the mentioned temperature effect (see also 5.1.10). The
same pertains to the liquid coolant.
NOTE 3 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.
NOTE 4 Values of L and L are obtained from the short-circuit impedance measurements on the converter
1 2
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 a.c. harmonic filters are connected, L also includes the a.c. system impedance. When
+AMD2:2016 CSV © IEC 2016
separate transformers supply the star and delta bridges and no additional line-side inductance is included, L = 0,
hence m = 0. When a three-winding transformer construction is employed a common winding impedance and
mutual coupling effects of the two secondary windings give non-zero values for L , which may be either positive or
negative. For more complicated transformer arra
...

IEC 61803 ®
Edition 1.1 2011-03
INTERNATIONAL
STANDARD
NORME
INTERNATIONALE
colour
inside
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 le réseau
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IEC 61803 ®
Edition 1.1 2011-03
INTERNATIONAL
STANDARD
NORME
INTERNATIONALE
colour
inside
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 le réseau
INTERNATIONAL
ELECTROTECHNICAL
COMMISSION
COMMISSION
ELECTROTECHNIQUE
PRICE CODE
INTERNATIONALE
CODE PRIX CM
ICS 29.200 ISBN 978-2-88912-338-4

– 2 – 61803 © IEC:1999+A1:2010

CONTENTS
FOREWORD . 4

1 Scope . 6

2 Normative references . 6

3 Definitions and symbols . 7

3.1 Definitions . 7

3.2 Letter symbols . 8

4 General . 8
4.1 Introduction . 8
4.2 Ambient conditions . 9
4.2.1 Outdoor standard reference temperature . 9
4.2.2 Coolant standard reference temperature . 9
4.2.3 Standard reference air pressure . 9
4.3 Operating parameters . 9
5 Determination of equipment losses . 10
5.1 Thyristor valve losses . 10
5.1.1 Thyristor conduction loss per valve . 11
5.1.2 Thyristor spreading loss per valve . 11
5.1.3 Other conduction losses per valve . 12
5.1.4 D.C. voltage-dependent loss per valve . 12
5.1.5 Damping loss per valve (resistor-dependent term) . 13
5.1.6 Damping loss per valve (change of capacitor energy term) . 14
5.1.7 Turn-off losses per valve . 14
5.1.8 Reactor loss per valve . 14
5.1.9 Total valve losses . 15
5.1.10 Temperature effects . 15
5.1.11 No-load operation loss per valve . 15
5.2 Converter transformer losses . 16
5.2.1 General . 16
5.2.2 No-load operation losses . 16
5.2.3 Operating losses . 16
5.2.4 Auxiliary power losses . 17
5.3 AC filter losses . 17

5.3.1 General . 17
5.3.2 AC filter capacitor losses . 18
5.3.3 AC filter reactor losses . 18
5.3.4 AC filter resistor losses . 19
5.3.5 Total a.c. filter losses . 19
5.4 Shunt capacitor bank losses . 19
5.5 Shunt reactor losses . 19
5.6 DC smoothing reactor losses . 19
5.7 DC filter losses . 20
5.7.1 General . 20
5.7.2 DC filter capacitor losses . 21
5.7.3 DC filter reactor losses . 21

61803 © IEC:1999+A1:2010 – 3 –

5.7.4 DC filter resistor losses . 21

5.7.5 Total d.c. filter losses . 21

5.8 Auxiliaries and station service losses . 22

5.9 Radio interference/PLC Series filter losse . 22

5.10 Other equipment losses . 23

Annex A (normative)  Calculation of harmonic currents and voltages . 29

Annex B (informative)  Typical station losses . 31

Annex C (informative)  Bibliography . 32

Figure 1 – Typical high-voltage direct current (HVDC) equipment for one pole (auxiliary
equipment is not shown) . 24
Figure 2 – Simplified three-phase diagram of an HVDC 12-pulse converter . 25
Figure 3 – Simplified equivalent circuit of a typical thyristor valve . 25
Figure 4 – Current and voltage waveforms of a valve operating in a 12-pulse converter
(commutation overshoots are not shown) . 26
Figure 5 – Thyristor on-state characteristic . 27
Figure 6 – Conduction current and voltage drop . 27
Figure 7 – Distribution of commutating inductance between L1 and L2 . 28
Figure 8 – Thyristor current during reverse recovery . 28

– 4 – 61803 © IEC:1999+A1:2010

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
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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
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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
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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.

This consolidated version of IEC 61803 consists of the first edition (1999) [documents
22F/51/FDIS and 22F/56/RVD], its amendment 1 (2010) [documents 22F/214/CDV and
22F/224/RVC] and its corrigendum of October 1999. It bears the edition number 1.1.
The technical content is therefore identical to the base edition and its amendment and
has been prepared for user convenience. A vertical line in the margin shows where the
base publication has been modified by amendment 1. Additions and deletions are
displayed in red, with deletions being struck through.

61803 © IEC:1999+A1:2010 – 5 –

International Standard IEC 61803 has been prepared by subcommittee 22F: Power
electronics for electrical transmission and distribution systems, of IEC technical committee 22:

Power electronics.
Annex A forms an integral part of this standard.

Annexes B and C are for information only.

The committee has decided that the contents of the base publication and its amendments will

remain unchanged until the stability date indicated on the IEC web site under
"http://webstore.iec.ch" in the data related to the specific publication. At this date, the

publication will be
• reconfirmed,
• withdrawn,
• replaced by a revised edition, or
• amended.
IMPORTANT – The “colour inside” logo on the cover page of this publication indicates
that it contains colours which are considered to be useful for the correct understanding
of its contents. Users should therefore print this publication using a colour printer.

– 6 – 61803 © IEC:1999+A1:2010

DETERMINATION OF POWER LOSSES IN HIGH-VOLTAGE

DIRECT CURRENT (HVDC) CONVERTER STATIONS WITH LINE-

COMMUTATED CONVERTERS
1 Scope
This International Standard applies to all line-commutated high-voltage direct current (HVDC)
converter stations used for power exchange in utility systems. This standard 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 a.c. bus of the HVDC converter station. The loss determination procedures
for such equipment are not included in this standard.
This standard presents a set of standard procedures for determining the total losses of an
HVDC converter station. Typical HVDC equipment is shown in figure 1. 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 standard, or designs equipped with unusual auxiliary
circuits that could affect the losses, shall be assessed on their own merits.
2 Normative references
The following referenced documents are indispensable for the application 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 60076-1:1993, Power transformers – Part 1: General
IEC 60076-6, Power transformers – Part 6: Reactors
IEC 60289:1988, Reactors
IEC 60633:1998, Terminology for high-voltage direct current (HVDC) transmission
IEC 60700-1:1998, Thyristor valves for high voltage direct current (HVDC) power transmission –
Part 1: Electrical testing
IEC 60747-6:1983, Semiconductor devices – Discrete devices – Part 6: Thyristors
IEC 60871-1:1997, Shunt capacitors for a.c. power systems having a rated voltage above
1 000 V – Part 1: General performance, testing and rating – Safety requirements – Guide for
installation and operation
61803 © IEC:1999+A1:2010 – 7 –

3 Definitions and symbols
For the purpose of this International Standard, the following definitions apply:

3.1 Definitions
3.1.1
auxiliary losses
the electric power required to feed the converter station auxiliary loads. The auxiliary losses

depend on 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
no-load operation losses
the losses produced in an item of equipment with the converter station energized but with the
converters blocked and all station service loads and auxiliary equipment connected as
required for immediate pick-up of load
3.1.3
load level
this term specifies the direct current, direct voltage, firing angle, a.c. voltage, and converter
transformer tap-changer position at which the converter station is operating
3.1.4
operating losses
the losses produced in an item of equipment at a given load level with the converter station
energized and the converters operating
3.1.5
rated load
this load is related to operation at nominal values of d.c. current, d.c. voltage, a.c. voltage and
converter firing angle. The a.c. 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 a.c. filters and shunt reactive elements connected shall be
consistent with operation at rated load, coincident with nominal conditions
3.1.6
total station losses
the total station loss is the sum of all operating or no-load operation losses and the
corresponding auxiliary losses

3.1.7
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 must remain working in case of complete loss of a.c.
power supply (e.g. battery chargers, operating mechanisms)
NOTE Total “operating losses” minus “no load operation losses” may be considered as being quantitatively
equivalent to “load losses” as in conventional a.c. substation practice.

– 8 – 61803 © IEC:1999+A1:2010

3.2 Letter symbols
α firing (trigger) delay angle, in radians (rad)

µ commutation overlap angle, in radians (rad)

f a.c. system frequency, in hertz (Hz)

I direct current, in the bridge d.c. connection, in amperes (A)
d
I harmonic r.m.s. current of order n, in amperes (A)
n
L the 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 a.c. harmonic filters
L the 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 the 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 (W) (Ω)
U direct voltage, in volts (V)
d
harmonic r.m.s. voltage of order n, in volts (V)
U
n
U r.m.s. 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 General
4.1 Introduction
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.
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 a.c. source and also
connected together via their d.c. terminals. In this connection, the power drawn from the a.c.
source equals the losses in the circuit. However, the a.c. source must also provide var
support and commutating voltage to the two converters. Once again, there are practical
measurement difficulties.
61803 © IEC:1999+A1:2010 – 9 –

In order to avoid the problems described above, this standard 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.
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
A set of standard reference ambient conditions shall be used for determining the power losses
in HVDC converter stations.
4.2.1 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.
NOTE 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.
4.2.2 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.
4.2.3 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 three categories, termed the no-
load operation losses, operating losses and auxiliary losses.
The operating losses and auxiliary losses are affected by the load level of the station because
the numbers of certain types of energized 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.

– 10 – 61803 © IEC:1999+A1:2010

HVDC converter station losses shall be determined for nominal (balanced) a.c. 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 a.c. 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 a.c.

voltage, d.c. 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 4.2.1
and 4.2.2), shall be assumed to be connected to support the respective load level.
For the no-load operation mode, converter transformers shall be energized 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.
5 Determination of equipment losses
5.1 Thyristor valve losses
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 subclauses 5.1.1 to 5.1.10, and no-load operation losses are dealt
with in 5.1.11. Auxiliary losses are dealt with in 5.8.
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.
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 d.c. grading resistors and other resistive
DC
components which incur loss when the valve blocks voltage. It also includes the effects of the
thyristor leakage current (see 5.1.4 and 5.1.11). C includes both stray capacitances and
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 and inverter 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 standard, 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.

61803 © IEC:1999+A1:2010 – 11 –

5.1.1 Thyristor conduction loss per valve

This loss component is the product of the conduction current i(t) and the corresponding ideal

on-state voltage as shown in figures 5 and 6. Formula P shall be used provided that the
V1a
d.c. bridge current is well smoothed. In the event that the root sum square value of the d.c.

side harmonic currents, determined in accordance with clause A.4 (annex A), exceeds 5 % of
the d.c. component, formula P shall be used instead.

V1b
N ×I  2π − µ 
 
t d
P = U + R ×I ×  
V1a  0 0 d 
3 2π
 
 
n=48
 
N ×I ×U N × R 2π − µ
 
t d 0 t 0 2 2
 
P = + I + I  
V1b n
d ∑
 
3 3 2π
 
 n=12 
where
U is the current-independent component of the on-state voltage of the average thyristor
(see note below), in volts;
R is the slope resistance of the on-state characteristic of the average thyristor (see note
below), in ohms;
I is the calculated r.m.s. value of the nth harmonic current in the bridge d.c. connection
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 appropriate
0 0
current and junction temperature. The average value of U and R is obtained from production records of the
0 0
thyristors manufactured for the specific project at 100 % and 50 % of nominal d.c. current. The temperature
dependence of U and R is established from type tests or routine tests on a statistically significant number of the
0 0
thyristors employed, and is used, where necessary, to correct U and R to the appropriate service junction
0 0
temperature. If parallel connection of p thyristors is employed, the appropriate 100 % current is the nominal d.c.
bridge current divided by p. The calculated result is then multiplied by p.
5.1.2 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).
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
u (t) is the instantaneous on-state voltage, in volts, of a thyristor whose fully spread on-state
B
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 figures 5
and 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.
NOTE 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

– 12 – 61803 © IEC:1999+A1:2010

obtained during the valve periodic firing and extinction type test (see IEC 60700-1) or, alternatively, from a

separate laboratory test on a statistically significant number of thyristors.

5.1.3 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
s  
d
P =
 
V3
3 2π
 
where
R is the d.c. 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.
5.1.4 D.C. voltage-dependent loss per valve
This loss component is the loss in the shunt resistance R of the valve (see figure 3), arising
DC
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 d.c.
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.
U  
4 3 6m − 12m − 7
 
v0
P = π + [cos(2α ) + cos(2α + 2µ)] + [sin(2α ) − sin(2α + 2µ) + 2µ]
 
V4
2π  R 3 4 8
 
DC
 
U  
4 3 6m − 12m− 7
 
v0
P = π + [cos (2α ) + cos (2α + 2µ)]+ [sin (2α ) − sin (2α + 2µ) + 2µ]
 
v4
2π  R 3 4 8
 
DC
 
where
R is the effective off-state d.c. resistance of a complete valve determined by measuring
DC
the current drawn during the valve terminal-to-terminal d.c. voltage type test (see IEC
60700) in ohms. If a type test is not performed on the thyristor valve, R shall be
DC
determined by reference to a previous type test (see also note 2 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 a.c. 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 notes 3 and 4 below).
2 2d 2y
NOTE 1 The equation for P is valid for µ < π/6 (30°) only.
V4
61803 © IEC:1999+A1:2010 – 13 –

NOTE 2 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 make later corrections to the measured value using the

DC
average thyristor data obtained separately, to include the mentioned temperature effect (see also 5.1.10). The

same pertains to the liquid coolant.

NOTE 3 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.

NOTE 4 Values of L and L are obtained from the short-circuit impedance measurements on the converter
1 2
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 a.c. harmonic filters are connected, L also includes the a.c. system impedance. When
separate transformers supply the star and delta bridges and no additional line-side inductance is included, L = 0,
hence m = 0. When a three-winding transformer construction is employed a common winding impedance and
mutual coupling effects of the two secondary windings give non-zero values for L , which may be either positive or
negative. For more complicated transformer arrangements, such as filters connected to a tertiary winding, the
values of L and L must be determined with care.
1 2
5.1.5 Damping loss per valve (resistor-dependent term)
This loss component depends on the value of the resistive elements of those circuits that are
a.c. coupled via series capacitors and on the voltage appearing between valve terminals
during the non-conduction interval.
2 2
 
 
4π 3 3 3m µ 7 9m 39m
 
 − + + (6m −12m − 7) + + − sin2α + 
 
3 2 8 4 8 4 32
 
   
2 2 2
P = 2πf U C R
 
V5 AC
v0 AC
2 2
   
 7 3m 3m 3m 3 3m 3m 
   
+ + sin(2α + 2µ)− + cos2α + cos(2α + 2µ)
 
   
8 4 32 16 8 16
 
   
 
where
C is the effective terminal-to-terminal value of valve damping capacitance, in farads (see
AC
figure 3);
R is the effective terminal-to-terminal value of the associated series-connected damping
AC
resistance, in ohms (see figure 3).
C shall be the design value of damping capacitance per level divided by the number of
AC
thyristor levels in a valve.
R shall be the design value of damping resistor per level multiplied by the number of
AC
thyristor levels in a valve.
If the valve employs more than one damping or grading network that incorporates series-
connected R-C branches, then each branch shall be evaluated separately and the results
summed.
If energy is extracted from the R-C grading network to energize the thyristor firing and/or
monitoring circuits, then either it shall be demonstrated that the additional losses are
negligible or the additional loss shall be calculated separately and added to the figure
obtained from the equation P .
V5
NOTE Notes 1, 3 and 4 in 5.1.4 also apply to P .
V5
– 14 – 61803 © IEC:1999+A1:2010

5.1.6 Damping loss per valve (change of capacitor energy term)

This loss component arises from the change in stored energy in the valve capacitances as a

result of the step changes (∆U) in the voltage blocked by the valve. Each step change incurs

energy loss which equals C × ∆U . The equation below is derived from the sum of the
energies lost due to the 12 voltage jumps which take place during one cycle of blocking

voltage (figure 4) multiplied by the system frequency.

2 2
U × f ×C × (7 + 6m )
HF
2 2
v0
P = [sin (α )+ sin (α + µ)]
V6
where
C is the sum of the effective terminal-to-terminal capacitance of all capacitive grading
HF
network branches within the valve (whether incorporating series resistors or not), plus
the total effective stray capacitance between valve terminals arising from externally
connected equipment and the vicinity of the valve to ground and/or adjacent objects
(see note 3). C = C + C (see figure 3).
HF AC S
NOTE 1 Notes 1, 3 and 4 in 5.1.4 also apply to P .
V6
NOTE 2 The equation for P produces overly pessimistic results for commutation overlaps whose length is
V6
shorter than 3 time-constants of the R-C damping network.
NOTE 3 The external stray capacitance arises predominantly from the winding and bushings of the converter
transformer (plus separate wall bushings if fitted), all of which can be measured at manufacture. Depending on the
design, stray capacitance between the valve and the earth may also have to be included. Surge arresters, busbars
and the valve structure contribute to the stray capacitance, but these contributions are small and may be neglected.
Since the effective stray capacitance is different for each row of valves, the a
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