IEC TR 60919-1:2005
(Main)Performance of high-voltage direct current (HVDC) systems with line-commutated converters - Part 1: Steady-state conditions
Performance of high-voltage direct current (HVDC) systems with line-commutated converters - Part 1: Steady-state conditions
provides general guidance on the steady-state performance requirements of HVDC systems. It concerns the steady-state performance of two-terminal HVDC systems utilizing 12-pulse converter units comprised of three-phase bridge (double- way) connections (see Figure 1), but it does not cover multi-terminal HVDC transmission systems. Both terminals are assumed to use thyristor valves as the main semiconductor valves and to have power flow capability in both directions. Diode valves are not considered in this report.
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Standards Content (Sample)
TECHNICAL IEC
REPORT TR
60919-1
Second edition
2005-03
Performance of high-voltage direct current (HVDC)
systems with line-commutated converters –
Part 1: Steady-state conditions
Reference number
IEC/TR 60919-1:2005(E)
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TECHNICAL IEC
REPORT TR
60919-1
Second edition
2005-03
Performance of high-voltage direct current (HVDC)
systems with line-commutated converters –
Part 1: Steady-state conditions
IEC 2005 Copyright - all rights reserved
No part of this publication may be reproduced or utilized in any form or by any means, electronic or
mechanical, including photocopying and microfilm, without permission in writing from the publisher.
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Commission Electrotechnique Internationale
XC
International Electrotechnical Commission
Международная Электротехническая Комиссия
For price, see current catalogue
– 2 – TR 60919-1 IEC:2005(E)
CONTENTS
FOREWORD.6
1 Scope .8
2 Normative references .10
3 Types of HVDC systems .10
3.1 General .10
3.2 HVDC back-to-back system .11
3.3 Monopolar earth return HVDC system .12
3.4 Monopolar metallic return HVDC system .14
3.5 Bipolar earth return HVDC system.15
3.6 Bipolar metallic return HVDC system.18
3.7 Two 12-pulse groups per pole .20
3.8 Converter transformer arrangements.20
3.9 DC switching considerations .20
3.10 Series capacitor compensated HVDC systems .25
4 Environment information .27
5 Rated power, current and voltage .31
5.1 Rated power.31
5.2 Rated current .31
5.3 Rated voltage .32
6 Overload and equipment capability .32
6.1 Overload .32
6.2 Equipment capability.33
7 Minimum power transfer and no-load stand-by state .34
7.1 General .34
7.2 Minimum current.34
7.3 Reduced direct voltage operation .35
7.4 No-load stand-by state.35
8 AC system.36
8.1 General .36
8.2 AC voltage .36
8.3 Frequency .37
8.4 System impedance at fundamental frequency.38
8.5 System impedance at harmonic frequencies.38
8.6 Positive and zero-sequence surge impedance .38
8.7 Other sources of harmonics .38
8.8 Subsynchronous torsional interaction (SSTI) .38
9 Reactive power.39
9.1 General .39
9.2 Conventional HVDC systems .39
9.3 Series capacitor compensated HVDC schemes .41
9.4 Converter reactive power consumption.41
TR 60919-1 IEC:2005(E) – 3 –
9.5 Reactive power balance with the a.c. system.41
9.6 Reactive power supply.42
9.7 Maximum size of switchable VAR banks.42
10 HVDC transmission line, earth electrode line and earth electrode .42
10.1 General .42
10.2 Overhead line(s).43
10.3 Cable line(s).43
10.4 Earth electrode line .44
10.5 Earth electrode.44
11 Reliability .44
11.1 General .44
11.2 Outage .44
11.3 Capacity.45
11.4 Outage duration terms .45
11.5 Energy unavailability (EU).46
11.6 Energy availability (EA).47
11.7 Maximum permitted number of forced outages .47
11.8 Statistical probability of outages.47
12 HVDC control .48
12.1 Control objectives.48
12.2 Control structure.48
12.3 Control order settings .54
12.4 Current limits.54
12.5 Control circuit redundancy .55
12.6 Measurements.55
13 Telecommunication.55
13.1 Types of telecommunication links.55
13.2 Telephone .56
13.3 Power line carrier (PLC) .56
13.4 Microwave .56
13.5 Radio link .57
13.6 Optical fibre telecommunication .57
13.7 Classification of data to be transmitted.57
13.8 Fast response telecommunication .58
13.9 Reliability .58
14 Auxiliary power supplies .58
14.1 General .58
14.2 Reliability and load classification.59
14.3 AC auxiliary supplies .60
14.4 Batteries and uninterruptible power supplies (UPS) .60
14.5 Emergency supply .61
15 Audible noise .61
15.1 General .61
15.2 Public nuisance .61
15.3 Noise in working areas .62
– 4 – TR 60919-1 IEC:2005(E)
16 Harmonic interference – AC .63
16.1 AC side harmonic generation .63
16.2 Filters.63
16.3 Interference disturbance criteria.67
16.4 Levels for interference .68
16.5 Filter performance .69
17 Harmonic interference – DC.69
17.1 DC side interference.69
17.2 DC filter performance.71
17.3 Specification requirements.72
18 Power line carrier interference (PLC) .75
18.1 General .75
18.2 Performance specification.76
19 Radio interference .77
19.1 Radio interference (RI) from HVDC systems.77
19.2 RI performance specification.78
20 Power losses.79
20.1 General .79
20.2 Main contributing sources .79
21 Provision for extensions to the HVDC systems .80
21.1 General .80
21.2 Specification for extensions .80
Bibliography .83
Figure 1 – Twelve-pulse converter unit .8
Figure 2 – Examples of back-to-back HVDC systems.11
Figure 3 – Monopolar earth return system .12
Figure 4 – Two 12-pulse units in series .13
Figure 5 – Two 12-pulse units in parallel .14
Figure 6 – Monopolar metallic return system .15
Figure 7 – Bipolar system .16
Figure 8 – Metallic return operation of the unfaulted pole in a bipolar system .18
Figure 9 – Bipolar metallic neutral system .19
Figure 10 – DC switching of line conductors .21
Figure 11 – DC switching of converter poles.22
Figure 12 – DC switching – Overhead line to cable .23
Figure 13 – DC switching – Two-bipolar converters and lines.24
Figure 14 – DC switching – Intermediate .25
Figure 15 – Capacitor commutated converter configurations .26
TR 60919-1 IEC:2005(E) – 5 –
Figure 16 – Variations of reactive power Q with active power P of an HVDC converter.40
Figure 17 – Control hierarchy.49
Figure 18 – Converter voltage-current characteristic.52
Figure 19 – Examples of a.c. filter connections for a bipole HVDC system.64
Figure 20 – Circuit diagrams for different filter types.66
Figure 21 – RY COM noise meter results averaged – Typical plot of converter noise
levels on the d.c. line corrected and normalized to 3 kHz bandwidth –0 dBm = 0,775 V .76
Figure 22 – Extension methods for HVDC systems .81
Table 1 – Information supplied for HVDC substation .28
Table 2 – Performance parameters for voice communication circuits: Subscribers and
trunk circuits.72
– 6 – TR 60919-1 IEC:2005(E)
INTERNATIONAL ELECTROTECHNICAL COMMISSION
____________
PERFORMANCE OF HIGH-VOLTAGE DIRECT CURRENT
(HVDC) SYSTEMS WITH LINE-COMMUTATED CONVERTERS –
Part 1: Steady-state conditions
FOREWORD
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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.
The main task of IEC technical committees is to prepare International Standards. However, a
technical committee may propose the publication of a technical report when it has collected
data of a different kind from that which is normally published as an International Standard, for
example "state of the art".
IEC 60919-1, which is a technical report, 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 1988, and constitutes
a technical revision.
This edition includes the following main changes with respect to the previous edition:
a) this report concerns only line-commutated converters;
b) significant changes have been made to the control system technology;
TR 60919-1 IEC:2005(E) – 7 –
c) some environmental constraints, for example audible noise limits, have been added;
d) the capacitor coupled converters (CCC) and controlled series capacitor converters (CSCC)
have been included.
The text of this technical report is based on the following documents:
Enquiry Draft Report on voting
22F/95A/DTR 22F/104/RVC
Full information on the voting for the approval of this technical report can be found in the
report on voting indicated in the above table.
This publication has been drafted in accordance with the ISO/IEC Directives, Part 2.
IEC 60919 consists of the following parts, under the general title: Performance of high-voltage
direct current (HVDC) systems with line-commutated converters:
Part 1: Steady-state conditions
Part 2: Faults and switching
Part 3: Dynamic conditions
The committee has decided that the contents of this publication will remain unchanged until
the maintenance result 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.
A bilingual version of this technical report may be issued at a later date.
———————
The National Committees are requested to note that for this publication the maintenance result date is 2010.
– 8 – TR 60919-1 IEC:2005(E)
PERFORMANCE OF HIGH-VOLTAGE DIRECT CURRENT
(HVDC) SYSTEMS WITH LINE-COMMUTATED CONVERTERS –
Part 1: Steady-state conditions
1 Scope
This technical report provides general guidance on the steady-state performance
requirements of HVDC systems. It concerns the steady-state performance of two-terminal
HVDC systems utilizing 12-pulse converter units comprised of three-phase bridge (double-
way) connections (see Figure 1), but it does not cover multi-terminal HVDC transmission
systems. Both terminals are assumed to use thyristor valves as the main semiconductor
valves and to have power flow capability in both directions. Diode valves are not considered
in this report.
IEC 385/05
Key
1 Transformer valve windings
Figure 1 – Twelve-pulse converter unit
Only line-commutated converters are covered in this report, which includes capacitor
commutated converter circuit configurations. General requirements for semiconductor line-
commutated converters are given in IEC 60146-1-1, IEC 60146-1-2 and IEC 60146-1-3.
Voltage-sourced converters are not considered.
This technical report, which covers steady-state performance, will be followed by additional
documents on dynamic performance and transient performance. All three aspects should be
considered when preparing two-terminal HVDC system specifications.
The difference between system performance specifications and equipment design specifi-
cations for individual components of a system should be realized. Equipment specifications
and testing requirements are not defined in this report. Also excluded from this report are
detailed seismic performance requirements. In addition, because there are many variations
between different possible HVDC systems, this report does not consider these in detail;
TR 60919-1 IEC:2005(E) – 9 –
consequently, it should not be used directly as a specification for a particular project, but
rather to provide the basis for an appropriate specification tailored to fit actual system
requirements.
Frequently, performance specifications are prepared as a single package for the two HVDC
substations in a particular system. Alternatively, some parts of the HVDC system can be
separately specified and purchased. In such cases, due consideration should be given to co-
ordination of each part with the overall HVDC system performance objectives and the
interface of each with the system should be clearly defined. Typical of such parts, listed in the
appropriate order of relative ease for separate treatment and interface definition, are:
a) d.c. line, electrode line and earth electrode;
b) telecommunication system;
c) converter building, foundations and other civil engineering work;
d) reactive power supply including a.c. shunt capacitor banks, shunt reactors, synchronous
and static VAR compensators;
e) a.c. switchgear;
f) d.c. switchgear;
g) auxiliary systems;
h) a.c. filters;
i) d.c. filters;
j) d.c. reactors;
k) converter transformers;
l) surge arresters;
m) series commutation capacitors;
n) valves and their ancillaries;
o) control and protection systems.
NOTE The last four items are the most difficult to separate, and, in fact, separation of these four may be
inadvisable.
A complete steady-state performance specification for a HVDC system should consider
Clauses 3 to 21 of this report.
Terms and definitions for high-voltage direct current (HVDC) transmission used in this report
are given in IEC 60633.
Since the equipment items are usually separately specified and purchased, the HVDC
transmission line, earth electrode line and earth electrode (see Clause 10) are included only
because of their influence on the HVDC system performance.
For the purpose of this report, an HVDC substation is assumed to consist of one or more
converter units installed in a single location together with buildings, reactors, filters, reactive
power supply, control, monitoring, protective, measuring and auxiliary equipment. While there
is no discussion of a.c. switching substations in this report, a.c. filters and reactive power
sources are included, although they may be connected to an a.c. bus separate from the HVDC
substation, as discussed in Clause 16.
– 10 – TR 60919-1 IEC:2005(E)
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 60146-1-1:1991, Semiconductor converters – General requirements and line commutated
converters – Part 1-1: Specifications of basic requirements
Amendment 1 (1996)
IEC 60146-1-2:1991, Semiconductor converters – General requirements and line commutated
converters – Part 1-2: Application guide
IEC 60146-1-3:1991, Semiconductor converters – General requirements and line commutated
converters – Part 1-3: Transformers and reactors
IEC 60633:1998, Terminology for high-voltage direct current (HVDC) transmission
IEC 61803:1999, Determination of power losses in high-voltage direct current (HVDC)
converter stations
CISPR 16 (all parts), Specification for radio disturbance and immunity measuring apparatus
and methods
ISO 1996-1: 2003, Acoustics – Description, measurement and assessment of environmental
noise – Part 1: Basic quantities and assessment procedures
CIGRE Brochure No. 139: Guide to the specification and design evaluation of AC filters for
HVDC systems
CIGRE Report 14-97: Protocol for reporting the operational performance of HVDC
transmission systems
3 Types of HVDC systems
3.1 General
This part of the specification should include the following basic data:
a) general information on the location of the HVDC substations and the purpose of the
project;
b) type of system needed, including a simple one-line diagram;
c) the number of 12-pulse converter units;
d) pertinent information derived from the discussion in this section.
Generally, in studies of projects of the types discussed in this report, economic considerations
should take into account the capital costs, the cost of losses, cost of outages and other
expected annual expenses.
In terms of the type of system, the relatively new development of “capacitor-commuted
converter (CCC)” and “controlled series capacitor converter (CSCC)” technology may be
suitable alternatives to a conventional HVDC scheme. These are described in 3.10.
TR 60919-1 IEC:2005(E) – 11 –
3.2 HVDC back-to-back system
In this arrangement there is no d.c. transmission line and both converters are located at one
site. The valves for both converters may be located in one valve hall, or even in one
integrated structure or separately as outdoor valves. Similarly, many other items for the two
converters, such as the control system, cooling equipment, auxiliary system, etc., may be
located in one area or even integrated in layout into configurations common to the two
converters. Circuit configurations may vary. Examples are given in Figure 2. The performance
and economics of these configurations differ and must be evaluated. DC filters are not
needed.
I I
d d
a) b)
I
d
I
d
1 1
c) d)
IEC 386/05
Key
1 DC reactor
Figure 2 – Examples of back-to-back HVDC systems
– 12 – TR 60919-1 IEC:2005(E)
The voltage and current ratings for a given power rating should be optimized to achieve the
lowest system cost, including the evaluated cost of losses. Ordinarily, the user does not need
to specify the direct voltage and current ratings, unless there are specific reasons to do so,
for example, for compatibility with an already existing station, to provide for a future extension
of for some other reason. Economics dictate that each converter will usually be a 12-pulse
converter unit. Where operating criteria require that the loss of one converter unit will not
cause loss of full power capability, large HVDC substations could be comprised of two or
more back-to-back systems. For this, some of the equipment of the back-to-back systems
can, for economic reasons, be located in the same area or even physically integrated, but
events which could cause a failure of equipment required by all back-to-back systems need to
be carefully considered and preventive measures taken where appropriate.
3.3 Monopolar earth return HVDC system
Cost considerations often lead to the adoption of a monopolar earth return system (Figure 3),
particularly for cable transmission which may be expensive.
I
d
1 (+) 1
(–)
2 F F 2
U
d
IEC 387/05
Key
1 DC reactor
2 DC filters
Figure 3 – Monopolar earth return system
The monopolar earth return configuration might also be the first stage in the development of a
bipolar scheme. Monopolar arrangements may include one or more 12-pulse units in series or
in parallel at the ends of the HVDC transmission (Figures 4 and 5). More than one 12-pulse
unit might be used
a) to ensure partial transmission capacity during converter unit outages;
b) to complete the project in stages;
c) because of the physical limitations of transformer transport.
TR 60919-1 IEC:2005(E) – 13 –
F 2
IEC 388/05
Key
1 DC reactor
2 DC filter
Figure 4 – Two 12-pulse units in series
– 14 – TR 60919-1 IEC:2005(E)
F 2
IEC 389/05
Key
1 DC reactor
2 DC filter
Figure 5 – Two 12-pulse units in parallel
This arrangement requires one or more d.c. reactors at each end of the HVDC overhead line
or cable; these are usually located on the high-voltage side. However, the d.c. reactors may
be located on the earth side if the resulting performance is acceptable. If the line is overhead,
d.c. filters are likely to be needed at each end (see Clause 17). It also requires an earth
electrode line and a continuously operable earth electrode at the two ends of the transmission
which involves consideration of issues such as corrosion, magnetic field effects, etc.
3.4 Monopolar metallic return HVDC system
This configuration (Figure 6) will generally be used
a) as the first stage in construction of a bipolar system and if long-term flow of earth current
is not desirable during the interim period, or
b) if the transmission line length is short enough to make it uneconomic and undesirable to
build earth electrode lines and earth electrodes, or
c) if the earth resistivity is high enough to impose an unacceptable economic penalty, or
TR 60919-1 IEC:2005(E) – 15 –
d) if long-term flow of earth current is unacceptable because of environmental and safety
requirements.
This configuration utilizes one high-voltage and one low-voltage conductor. The neutral is
connected at one of the two HVDC substations to its station earth or, alternatively, to the
associated earth electrode. The other HVDC substation neutral is connected to its station
earth through a capacitor or an arrester or both.
DC reactors are needed at both ends of the high-voltage conductor. However, the d.c. reactor
may be located on the earth side if the resulting performance is acceptable. DC filters may be
needed if the HVDC transmission line is overhead.
If this configuration is the first stage of a bipolar system, its neutral conductor could be
insulated for the high voltage at this stage of development.
I
d
1 1
F 2 F 2
IEC 390/05
Key
1 DC reactor
2 DC filter
3 Station earth
4 Arrester
Figure 6 – Monopolar metallic return system
3.5 Bipolar earth return HVDC system
This is the most commonly used arrangement when a d.c. transmission line connects two
HVDC substations and electrodes for earth return operation are provided (Figure 7). It is
effectively equivalent to a double-circuit a.c. transmission. It reduces harmonic interference
from the d.c. line as compared with monopolar operation and it keeps earth current flow down
to a low value. When combined, two monopolar earth return schemes give a bipolar scheme.
– 16 – TR 60919-1 IEC:2005(E)
I
d
1 (+) 1
(–)
2 2
F F
U
d
3 3
2 2
F F
1 1
IEC 391/05
Key
1 DC reactor
2 DC filter
3 Earth electrodes
Figure 7 – Bipolar system
For power flow in one direction, one pole has positive polarity to earth and the other pole has
negative polarity to earth. For power flow in the other direction, the two poles reverse their
polarities. When both poles are in operation, the unbalance current flow in the earth path can
be kept at a very low value.
This configuration offers a number of emergency operating modes. Consequently, the follow-
ing requirements should be considered in the specifications.
a) During an outage of one HVDC transmission line pole, the converter equipment of the
other pole should be capable of continuous operation with earth return.
b) If long-term flow of earth current is undesirable and if the defective line pole still retains
some low-voltage insulating capability, the bipolar system should be capable of operation
in the monopolar metallic return mode (Figure 8). To switch into this emergency operating
mode the conductor of the off-pole is first connected in parallel with the earth path and
then the earth path is interrupted to transfer the current to the metallic path (through the
conductor of the off-pole). Load transfer without interruption requires a metallic return
transfer breaker (MRTB) at one terminal of the d.c. transmission. If a short interruption of
TR 60919-1 IEC:2005(E) – 17 –
power flow is permitted, MRTB would not be necessary. The neutral equipment at the
MRTB end of the HVDC transmission system should be insulated from earth for a
somewhat higher voltage than at the other end of the system.
c) During maintenance of the earth electrode(s) or the earth electrode line(s), operation of
the bipolar system should be possible with the station neutral(s)connected to the station
earth at one or both HVDC substations as long as the unbalance current between the two
poles entering the station earth(s) is kept at a very low value. The unbalance current
should be kept low to avoid saturation effects in the converter transformers from the flow
of part of the unbalance current through the transformer neutrals. ln this arrangement
when one transmission line of substation pole is lost, both poles should be blocked
automatically.
d) In bipolar operation with both earth electrodes connected, the two poles of the HVDC
system should be capable of operation with substantially different currents in each pole.
This may be necessary if loss of cooling or some other unusual condition prevents the
operation of one pole with full current.
e) If continuation of operation is required in the case where the line insulation has been
partially damaged, the converters should be designed for continuous operation at reduced
voltage, so that either pole can be operated at reduced voltage (see 7.3).
f) ln the event of the loss of one transmission line pole, the two substation poles can also be
connected in parallel by using appropriate switches for polarity reversal in at least one
station pole enabling both poles to operate in the monopolar earth return mode. This,
however, requires that the d.c. terminals of each 12-pulse group be insulated for the full
pole voltage and the line and the earth electrode shall be thermally capable of carrying a
current higher than the normal current.
A d.c. reactor is needed at each end of the system in each pole, and if the HVDC system
includes an overhead line, a d.c. filter would most likely be needed. One 12-pulse unit per
pole is most commonly used; however, large capacity systems or staged expansion may
require 12-pulse units in series or in parallel (Figures 4 and 5).
– 18 – TR 60919-1 IEC:2005(E)
I
d
1 1
2 2
F F
MRTB
2 F F 2
IEC 392/05
Key
1 DC reactor
2 DC filter
3 Operating pole
4 RTB Metallic return transfer breaker
Figure 8 – Metallic return operation of the unfaulted pole in a bipolar system
3.6 Bipolar metallic return HVDC system
If earth currents are not tolerable (as mentioned in 3.4, item d)) or if the distance between the
HVDC system terminals is short, or if an earth electrode is not feasible because of high earth
resistivity, then the transmission line may be constructed with a third conductor to give a
bipolar metallic return HVDC system (Figure 9). The third conductor carries unbalance
currents during bipolar operation. It also serves as the return path when one transmission line
pole is out of service. This third conductor requires only reduced voltage insulation and, in
this case, may also serve as a shield wire if the line is overhead. However, if it is fully
insulated, it can serve as a spare conductor. In this case, a separate shield wire is required.
TR 60919-1 IEC:2005(E) – 19 –
I
d
1 1
2 2
F F
F F
2 2
1 1
IEC 393/05
Key
1 DC reactor
2 DC filter
3 Metallic neutral
4 Arrester
Figure 9 – Bipolar metallic neutral system
The neutral of one of the two HVDC substations should be earthed, while the neutral at the
other end of the transmission would float or be tied to its station earth through an arrester, a
capacitor or both.
With this design, the system can still be operated in the bipolar mode, if one conductor
becomes unavailable and the third conductor is fully insulated. Then, the neutrals at both
terminals should be connected to their local station earths, and care should be taken to hold
the unbalance current flow to very low values. Loss of one pole will require blocking of the
other pole until the necessary switching has taken place for operation of the remaining sound
portions of the HVDC transmission system.
If one substation pole becomes unavailable, the system can be operated in monopolar
metallic return mode by utilizing the other substation pole.
– 20 – TR 60919-1 IEC:2005(E)
3.7 Two 12-pulse groups per pole
For a large bipole capacity, two 12-pulse units in series per pole may be considered. This
means that when a forced or scheduled outage of a 12-pulse converter occurs, only 25 % of
the capacity will be lost and the two poles can still operate with balanced current (without
earth current). If sufficient overload capability is available, full power or almost full
...
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