IEC 61954:2021
(Main)Static VAR compensators (SVC) - Testing of thyristor valves
Static VAR compensators (SVC) - Testing of thyristor valves
IEC 61954:2021 defines type, production and optional tests on thyristor valves used in thyristor controlled reactors (TCR), thyristor switched reactors (TSR) and thyristor switched capacitors (TSC) forming part of static VAR compensators (SVC) for power system applications. The requirements of the document apply both to single valve units (one phase) and to multiple valve units (several phases). Clauses 4 to 7 detail the type tests, i.e. tests which are carried out to verify that the valve design meets the requirements specified. Clause 8 covers the production tests, i.e. tests which are carried out to verify proper manufacturing. Clauses 9 and 10 detail optional tests, i.e. tests additional to the type and production tests. This edition includes the following significant technical changes with respect to the previous edition: important clarifications were made in 4.4.1.2, 5.1.2.2, 5.1.3.2, 5.2.3.2, 6.1.2.2, 6.1.2.4, 6.1.3.2, 6.2.2.2, 6.2.2.4, 6.3.2.2 and 9.3.2.
The contents of the corrigendum of June 2024 have been included in this copy.
Compensateurs statiques de puissance réactive (SVC) - Essais des valves à thyristors
L'IEC 61954:2021 définit les essais de type, les essais de production et les essais facultatifs des valves à thyristors utilisées dans les bobines d'inductance commandées par thyristors (TCR - thyristor controlled reactor), les bobines d'inductance commutées par thyristors (TSR - thyristor switched reactor) et les condensateurs commutés par thyristors (TSC - thyristor switched capacitor) qui font partie des compensateurs statiques de puissance réactive (SVC - static VAR compensator) pour des applications de système de puissance. Les exigences du présent document s'appliquent tant aux unités à valve unique (monophasées) qu'aux unités à valves multiples (polyphasées). Les Articles 4 à 7 décrivent les essais de type, c’est-à-dire les essais effectués pour assurer que la conception des valves satisfait aux exigences spécifiées. L’Article 8 traite des essais de production, c'est-à-dire les essais effectués pour assurer que la fabrication est correcte. Les Articles 9 et 10 décrivent des essais facultatifs, c’est-à-dire des essais supplémentaires aux essais de type et de production. Cette édition inclut les modifications techniques majeures suivantes par rapport à l’édition précédente: d’importantes clarifications ont été apportées en 4.4.1.2, 5.1.2.2, 5.1.3.2, 5.2.3.2, 6.1.2.2, 6.1.2.4, 6.1.3.2, 6.2.2.2, 6.2.2.4, 6.3.2.2 et 9.3.2.
Le contenu du corrigendum de juin 2024 a été pris en considération dans cet exemplaire.
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IEC 61954 ®
Edition 3.0 2021-10
REDLINE VERSION
INTERNATIONAL
STANDARD
colour
inside
Static VAR compensators (SVC) – Testing of thyristor valves
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IEC 61954 ®
Edition 3.0 2021-10
REDLINE VERSION
INTERNATIONAL
STANDARD
colour
inside
Static VAR compensators (SVC) – Testing of thyristor valves
INTERNATIONAL
ELECTROTECHNICAL
COMMISSION
ICS 29.240.99; 31.080.20 ISBN 978-2-8322-5023-5
– 2 – IEC 61954:2021 RLV © IEC 2021
CONTENTS
FOREWORD . 5
1 Scope . 7
2 Normative references. 7
3 Terms and definitions . 7
4 General requirements for type, production and optional tests . 9
4.1 Summary of tests . 9
4.2 Objectives of tests . 10
4.2.1 General . 10
4.2.2 Dielectric tests . 10
4.2.3 Operational tests . 10
4.2.4 Electromagnetic interference tests . 11
4.2.5 Production tests . 11
4.2.6 Optional tests. 11
4.3 Guidelines for the performance of type and optional tests . 11
4.4 Test conditions . 12
4.4.1 General . 12
4.4.2 Valve temperature at testing . 13
4.4.3 Redundant thyristor levels . 14
4.5 Permissible component failures during type testing . 14
4.6 Documentation of test results . 14
4.6.1 Test reports to be issued . 14
4.6.2 Contents of a type test report . 15
5 Type tests on TCR and TSR valves . 16
5.1 Dielectric tests between valve terminals and earth . 16
5.1.1 General . 16
5.1.2 AC test . 16
5.1.3 Lightning impulse test . 17
5.2 Dielectric tests between valves (MVU only) . 17
5.2.1 General . 17
5.2.2 AC test . 17
5.2.3 Lightning impulse test . 18
5.3 Dielectric tests between valve terminals . 18
5.3.1 General . 18
5.3.2 AC test . 18
5.3.3 Switching impulse test . 20
5.4 Operational tests . 21
5.4.1 Periodic firing and extinction test . 21
5.4.2 Minimum AC voltage test . 23
5.4.3 Temperature rise test . 23
6 Type tests on TSC valves . 24
6.1 Dielectric tests between valve terminals and earth . 24
6.1.1 General . 24
6.1.2 AC-DC test . 24
6.1.3 Lightning impulse test . 26
6.2 Dielectric tests between valves (for MVU only) . 27
6.2.1 General . 27
6.2.2 AC-DC test . 27
6.2.3 Lightning impulse test . 29
6.3 Dielectric tests between valve terminals . 30
6.3.1 General . 30
6.3.2 AC-DC test . 30
6.3.3 Switching impulse test . 33
6.4 Operational tests . 34
6.4.1 Overcurrent tests . 34
6.4.2 Minimum AC voltage test . 37
6.4.3 Temperature rise test . 38
7 Electromagnetic interference tests . 38
7.1 Objectives . 38
7.2 Test procedures . 38
7.2.1 General . 38
7.2.2 Switching impulse test . 39
7.2.3 Non-periodic firing test . 39
8 Production tests . 39
8.1 General . 39
8.2 Visual inspection . 39
8.3 Connection check . 39
8.4 Voltage-dividing/damping circuit check . 40
8.5 Voltage withstand check . 40
8.6 Check of auxiliaries . 40
8.7 Firing check . 40
8.8 Cooling system pressure test . 40
8.9 Partial discharge tests . 40
9 Optional tests on TCR and TSR valves . 40
9.1 Overcurrent test . 40
9.1.1 Overcurrent with subsequent blocking . 40
9.1.2 Overcurrent without blocking . 41
9.2 Positive voltage transient during recovery test . 41
9.2.1 Objectives . 41
9.2.2 Test values and waveshapes . 41
9.2.3 Test procedures . 42
9.3 Non-periodic firing test . 42
9.3.1 Objectives . 42
9.3.2 Test values and waveshapes . 42
9.3.3 Test procedures . 43
10 Optional tests on TSC valves . 44
10.1 Positive voltage transient during recovery test . 44
10.1.1 Test objective . 44
10.1.2 Test values and waveshapes . 44
10.1.3 Test procedures . 44
10.2 Non-periodic firing test . 44
10.2.1 Objectives . 44
10.2.2 Test values and waveshapes . 45
10.2.3 Test procedures . 46
– 4 – IEC 61954:2021 RLV © IEC 2021
Figure 1 – TSC branch . 35
Figure 2 – One-loop overcurrent . 36
Figure 3 – Two-loop overcurrent . 37
Table 1 – List of tests . 9
Table 2 – Number of thyristor levels permitted to fail during type tests . 15
INTERNATIONAL ELECTROTECHNICAL COMMISSION
____________
STATIC VAR COMPENSATORS (SVC) –
TESTING OF THYRISTOR VALVES
FOREWORD
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This redline version of the official IEC Standard allows the user to identify the changes made to
the previous edition IEC 61954:2011+AMD1:2013+AMD2:2017 CSV. A vertical bar appears in the
margin wherever a change has been made. Additions are in green text, deletions are in
strikethrough red text.
– 6 – IEC 61954:2021 RLV © IEC 2021
International Standard IEC 61954 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 third edition cancels and replaces the second edition published in 2011,
Amendment 1:2013 and Amendment 2:2017. This edition constitutes a technical revision.
This edition includes the following significant technical changes with respect to the previous
edition: important clarifications were made in 4.4.1.2, 5.1.2.2, 5.1.3.2, 5.2.3.2, 6.1.2.2,
6.1.2.4, 6.1.3.2, 6.2.2.2, 6.2.2.4, 6.3.2.2 and 9.3.2.
The text of this International Standard is based on the following documents:
FDIS Report on voting
22F/642/FDIS 22F/658/RVD
Full information on the voting for the approval of this International Standard can be found in
the report on voting indicated in the above table.
The language used for the development of this International Standard is English.
This document was drafted in accordance with ISO/IEC Directives, Part 2, and developed in
accordance with ISO/IEC Directives, Part 1 and ISO/IEC Directives, IEC Supplement,
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the specific document. At this date, the document will be
• reconfirmed,
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• replaced by a revised edition, or
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IMPORTANT – The 'colour inside' logo on the cover page of this publication indicates that it
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The contents of the corrigendum 1 (2024-06) have been included in this copy.
STATIC VAR COMPENSATORS (SVC) –
TESTING OF THYRISTOR VALVES
1 Scope
This document defines type, production and optional tests on thyristor valves used in thyristor
controlled reactors (TCR), thyristor switched reactors (TSR) and thyristor switched capacitors
(TSC) forming part of static VAR compensators (SVC) for power system applications. The
requirements of the document apply both to single valve units (one phase) and to multiple
valve units (several phases).
Clauses 4 to 7 detail the type tests, i.e. tests which are carried out to verify that the valve
design meets the requirements specified. Clause 8 covers the production tests, i.e. tests
which are carried out to verify proper manufacturing. Clauses 9 and 10 detail optional tests,
i.e. tests additional to the type and production tests.
2 Normative references
The following documents are referred to in the text in such a way that some or all of their
content constitutes requirements of this document. For dated references, only the edition
cited applies. For undated references, the latest edition of the referenced document (including
any amendments) applies.
IEC 60060 (all parts), High-voltage test techniques
IEC 60060-1:2010, High-voltage test techniques – Part 1: General definitions and test
requirements
IEC 60060-2, High-voltage test techniques – Part 2: Measuring systems
IEC 60071 (all parts), Insulation co-ordination
IEC 60071-1:20062019, Insulation co-ordination – Part 1: Definitions, principles and rules
IEC 60071-1:2006/AMD1:2010
IEC 60270, High-voltage test techniques – Partial discharge measurements
IEC 60700-1:2015, Thyristor valves for high-voltage direct current (HVDC) power transmission
– Part 1: Electrical testing
3 Terms and definitions
For the purposes of this document, the following terms and definitions apply.
ISO and IEC maintain terminological databases for use in standardization at the following
addresses:
• IEC Electropedia: available at http://www.electropedia.org/
• ISO Online browsing platform: available at http://www.iso.org/obp
– 8 – IEC 61954:2021 RLV © IEC 2021
3.1
thyristor level
part of a thyristor valve comprising a thyristor, or thyristors connected in parallel or anti-
parallel, together with their immediate auxiliaries and reactor, if any
3.2
thyristor (series) string
series connected thyristors forming one direction of a thyristor valve
3.3
valve reactor
reactor incorporated within some valves for limitation of stresses
Note 1 to entry: For testing purposes it is considered an integral part of the valve.
3.4
valve section
electrical assembly, comprising a number of thyristors and other components, which exhibits
pro-rated electrical properties of a complete thyristor valve, but only a portion of the full
voltage blocking capability of the thyristor valve, and which can be used for tests
3.5
thyristor valve
electrically and mechanically combined assembly of thyristor levels, complete with all
connections, auxiliary components and mechanical structures, which can be connected in
series with each phase of the reactor or capacitor of an SVC
3.6
valve structure
physical structure which insulates the valves to the appropriate level above earth potential
and from each other
3.7
valve base electronics
VBE
electronic unit, at earth potential, which is the interface between the control system of the
SVC and the thyristor valves
3.8
multiple valve unit
MVU
assembly of several valves in the same physical structure which cannot be separated for test
purposes (e.g. three-phase valves)
3.9
redundant thyristor levels
maximum number of thyristor levels in the thyristor valve that may be short-circuited,
externally or internally, during service without affecting the safe operation of the thyristor
valve as demonstrated by type tests; and which if and when exceeded, would require either
the shutdown of the thyristor valve to replace the failed thyristors, or the acceptance of
increased risk of failures
3.10
voltage breakover (VBO) protection
means of protecting the thyristors from excessive voltage by firing them at a predetermined
voltage
4 General requirements for type, production and optional tests
4.1 Summary of tests
Table 1 lists the tests given in the following clauses and subclauses.
Table 1 – List of tests
Test Subclause Test object
TCR/TSR TSC
Dielectric tests between valve terminals and earth (type tests)
AC test 5.1.2 Valve
AC-DC test 6.1.2 Valve
Lightning impulse test 5.1.3 6.1.3 Valve
Dielectric tests between valves (MVU only) (type tests)
AC test 5.2.2 MVU
AC-DC test 6.2.2 MVU
Lightning impulse test 5.2.3 6.2.3 MVU
Dielectric tests between valve terminals (type tests)
AC test 5.3.2 Valve
AC-DC test 6.3.2 Valve
Switching impulse test 5.3.3 6.3.3 Valve
Operational tests (type tests)
Periodic firing and extinction test 5.4.1 Valve or valve section
Overcurrent test 6.4.1 Valve or valve section
Minimum AC voltage test 5.4.2 6.4.2 Valve or valve section
Temperature rise test 5.4.3 6.4.3 Valve or valve section
Electromagnetic interference tests (type tests)
Switching impulse test 7.2.2 7.2.2 Valve
Non-periodic firing test 7.2.3 7.2.3 Valve
Production tests
Visual inspection 8.2 8.2
Connection check 8.3 8.3
Voltage dividing/damping circuit check 8.4 8.4
Voltage withstand check 8.5 8.5
Check of auxiliaries 8.6 8.6
Firing check 8.7 8.7
Cooling system pressure test 8.8 8.8
Partial discharge tests 8.9 8.9
Optional tests
Overcurrent test 9.1 Valve or valve section
Positive voltage transient during recovery test 9.2 10.1 Valve or valve section
Non-periodic firing test 9.3 10.2 Valve or valve section
– 10 – IEC 61954:2021 RLV © IEC 2021
4.2 Objectives of tests
4.2.1 General
The tests described apply to the valve (or valve sections), the valve structure and those parts
of the coolant distribution system and firing and monitoring circuits which are contained within
the valve structure or connected between the valve structure and earth. Other equipment,
such as valve control and protection and valve base electronics may be essential for
demonstrating the correct function of the valve during the tests but are not in themselves the
subject of the tests.
4.2.2 Dielectric tests
4.2.2.1 General
Tests for the following dielectric stresses are specified:
– AC voltage;
– combined AC and DC voltage (TSC only);
– impulse voltages.
In the interest of standardization with other equipment, lightning impulse tests between valve
terminals and earth and between phases of an MVU are included. For tests between valve
terminals, the only impulse test specified is a switching impulse.
4.2.2.2 Tests on valve structure
Tests are defined for the voltage withstand requirements between a valve (with its terminals
short-circuited) and earth, and also between valves for MVU. The tests shall demonstrate
that:
– sufficient clearances have been provided to prevent flashovers;
– there is no disruptive discharge in the insulation of the valve structure, cooling ducts, light
guides and other insulation parts of the pulse transmission and distribution systems;
– partial discharge inception and extinction voltages under AC and DC conditions are above
the maximum steady-state operating voltage appearing on the valve structure.
4.2.2.3 Tests between valve terminals
The purpose of these tests is to verify the design of the valve with respect to its capability to
withstand overvoltages between its terminals. The tests shall demonstrate that:
– sufficient internal insulation has been provided to enable the valve to withstand specified
voltages;
– partial discharge inception and extinction voltages under AC and DC conditions are above
the maximum steady-state operating voltage appearing between valve terminals;
– the protective overvoltage firing system (if provided) works as intended;
– the thyristors have adequate du/dt capability for in-service conditions. (In most cases the
specified tests are sufficient; however, in some exceptional cases additional tests may be
required.)
4.2.3 Operational tests
The purpose of these tests is to verify the valve design for combined voltage and current
stresses under normal and abnormal repetitive conditions as well as under transient fault
conditions. They shall demonstrate that, under specified conditions:
– the valve functions properly;
– the turn-on and turn-off voltage and current stresses are within the capabilities of the
thyristors and other internal circuits;
– the cooling provided is adequate and no component is overheated;
– the overcurrent withstand capability of the valve is adequate.
4.2.4 Electromagnetic interference tests
The principal objective of these tests is to demonstrate the immunity of the valve to
electromagnetic interference from within the valve and from outside the valve. Generally,
immunity to electromagnetic interference is demonstrated by monitoring of the valve during
other tests.
4.2.5 Production tests
The objective of tests is to verify proper manufacture. The production tests shall demonstrate
that:
– all materials, components and sub-assemblies used in the valve have been correctly
installed;
– the valve equipment functions as intended, and predefined parameters are within
prescribed acceptance limits;
– thyristor levels and valve or valve sections have the necessary voltage withstand
capability;
– consistency and uniformity in production is achieved.
4.2.6 Optional tests
Optional tests are additional tests which may be performed, subject to agreement between the
purchaser and the supplier. The objectives are the same as for the operational tests specified
in 4.2.3. The test object is normally one valve or appropriate equivalent number of valve
sections.
4.3 Guidelines for the performance of type and optional tests
The following principles shall apply:
– type tests shall be performed on at least one valve or on an appropriate number of valve
sections, as indicated in Table 1 (see 4.1), to verify that the valve design meets the
specified requirements. All type tests shall be performed on the same valve(s) or valve
section(s);
– provided that the valve is demonstrably similar to one previously tested, the supplier may
submit a certified report of any previous type test, at least equal to the requirements
specified in the contract, in lieu of the type test;
– for type tests performed on valve sections, the total number of thyristor levels subjected to
such type tests shall be at least equal to the number of thyristor levels in a valve;
– the valve or valve sections used for type tests shall first pass all production tests. On
completion of the type test programme, the valve or valve sections shall be checked again
for compliance with the production test criteria;
– material for the type tests shall be selected at random;
– the dielectric tests shall be performed in accordance with IEC 60060-1 and IEC 60060-2
where applicable;
– individual tests may be performed in any order.
NOTE Tests involving partial discharge measurement may provide added confidence if performed at the end of
the dielectric type test programme.
– 12 – IEC 61954:2021 RLV © IEC 2021
4.4 Test conditions
4.4.1 General
4.4.1.1 Dielectric test objects
Dielectric tests shall be performed on completely assembled valves, whereas some
operational tests may be performed on either complete valves or valve sections.
The valve shall be assembled with all auxiliary components except for the valve arrester, if
used. Unless otherwise specified, the valve electronics shall be energized. The cooling and
insulating fluids in particular shall be in a condition that represents service conditions such as
conductivity, except for the flow rate and anti-freezing media content, which can be reduced.
If any object or device external to the structure is necessary for proper representation of the
stresses during the test, it shall also be present or simulated in the test. Metallic parts of the
valve structure (or other valves in an MVU) which are not part of the test shall be shorted
together and connected to earth in a manner appropriate to the test in question.
4.4.1.2 Atmospheric correction
When specified in the relevant clause, Atmospheric correction shall be applied to the test
voltages in accordance with IEC 60060-1, except when specifically excluded. The reference
conditions to which correction shall be made are the following To calculate the test values
applicable at standard reference atmosphere, the methods described in IEC 60060-
1:2010,4.3.3.1 shall be used, considering the following conditions as input values for pressure
p, temperature t and humidity h:
– pressure:
If the insulation coordination of the tested part of the thyristor valve is based on standard
rated withstand voltages according to IEC 60071-1, correction factors are only applied for
altitudes exceeding 1 000 m. Hence if the altitude of the site a at which the equipment will
s
be installed is less than 1 000 m, then the standard atmospheric air pressure (b = 101,3
kPa) shall be used with no correction for altitude. If a >1 000 m, then the standard
s
procedure according to IEC 60060-1 is used except that the reference atmospheric
pressure b is replaced by the atmospheric pressure corresponding to an altitude of
1 000 m (b ).
1 000 m
If the insulation coordination of the tested part of the thyristor valve is not based on
standard rated withstand voltages according to IEC 60071-1, then the standard procedure
according to IEC 60060-1 is used with the reference atmospheric pressure b
(b = 101,3 kPa).
– temperature:
design maximum valve hall air temperature (°C).
– humidity:
design minimum valve hall absolute humidity (g/m ).
The values to be used shall be specified by the supplier.
In any of the afore mentioned cases, the correction of test values from standard reference
atmosphere to test conditions shall be as per IEC 60060-1:2010,4.3.3.2.
Where non-standard test levels are defined by this document, a site air density correction
, defined below shall be applied where stated.
factor k
d
The value of k shall be determined from the following formula:
d
b 273 + T
1 2
k = ×
(1)
d
b 273 + T
2 1
where
b is the laboratory ambient air pressure, in pascals (Pa);
T is the laboratory ambient air temperature, in degrees Celsius (°C);
b is the standard reference atmosphere of 101,3 kPa (i.e. 1 013 mbar), corrected to the
altitude of the site at which the equipment will be installed;
T is the design maximum valve hall air temperature, in degrees Celsius (°C).
Correction factors should shall not be applied either to the dielectric tests between valve
terminals or to the long duration dielectric tests whose primary purpose is to check for the
internal insulation and partial discharges.
The atmospheric correction factors shall not be applied to operational tests or optional tests.
4.4.1.3 Operational tests
Where possible, a complete thyristor valve should be tested. Otherwise the tests may be
performed on thyristor valve sections. The choice depends mainly upon the thyristor valve
design and the test facilities available. Where tests on the thyristor valve sections are
proposed, the tests specified in this standard are valid for thyristor valve sections containing
five or more series-connected thyristor levels. If tests on thyristor valve sections with fewer
than five thyristor levels are proposed, additional test safety factors shall be agreed upon.
Under no circumstances shall the number of series-connected thyristor levels in a thyristor
valve section be less than three.
Sometimes, operational tests may be performed at a power frequency different from the
service frequency, e.g. 50 Hz instead of 60 Hz. Some operational stresses such as switching
losses or I t of short-circuit current are affected by the actual power frequency during tests.
When this situation occurs, the test conditions shall be reviewed, and appropriate changes
made to ensure that the valve stresses are at least as severe as they would be if the tests
were performed at the service frequency.
The coolant shall be in a condition representative of service conditions. Flow and
temperature, in particular, shall be set to the most unfavourable values appropriate to the test
in question. Anti-freezing media content should, preferably, be equivalent to the service
condition; however, where this is not practicable, a correction factor agreed between the
supplier and the purchaser shall be applied.
The atmospheric correction factors are not applicable to operational tests.
4.4.2 Valve temperature at testing
4.4.2.1 Valve temperature for dielectric tests
Unless specified otherwise, tests shall be performed at room temperature.
4.4.2.2 Valve temperature for operational tests
Unless specified otherwise, tests shall be carried out under the conditions that produce the
highest component temperature that may occur in real operation.
If several components are to be verified by a test, it may be necessary to carry out the same
test under different conditions.
– 14 – IEC 61954:2021 RLV © IEC 2021
4.4.3 Redundant thyristor levels
4.4.3.1 Dielectric tests
All dielectric tests on a complete valve shall be carried out with redundant thyristor levels
short-circuited, except where otherwise indicated.
4.4.3.2 Operational tests
For operational tests, redundant thyristor levels should not be short-circuited. The test
voltages and circuit impedances used shall be adjusted by means of a scaling factor k .
n
N
tot
(2)
k =
n
N − N
t r
where
N is the total number of series thyristor levels in the test object;
tot
N is the total number of series thyristor levels in the valve;
t
N is the total number of redundant series thyristor levels in the valve.
r
NOTE In thyristor valves with a small number of thyristor levels, where the redundancy is a significant portion of
the total, this may cause certain valve components to be overstressed. As an alternative, it is therefore acceptable
to perform the operational test with redundant thyristor levels short-circuited and without scaling the test voltages
and impedances by k .
n
4.5 Permissible component failures during type testing
Experience in industry shows that, even with the most careful design of valves, it is not
possible to avoid occasional random failures of thyristor level components during service
operation. Even though these failures may be stress-related, they are considered random to
the extent that the cause of failure or the relationship between failure rate and stress cannot
be predicted or is not amenable to precise quantitative definition. Type tests subject valves or
valve sections, within a short time, to multiple stresses that generally correspond to the worst
stresses that can be experienced by the equipment not more than a few times during the life
of the valve. Considering the above, the criteria for successful type testing set out below
therefore permit a small number of thyristor levels to fail during type testing, providing that the
failures are essentially random and do not show any pattern that is indicative of inadequate
design.
The valves or valve sections shall be checked before each test, after any preliminary
calibration tests, and again after each type test to determine whether or not any thyristors or
auxiliary components have failed during the test. Failed thyristors or auxiliary components
found at the end of a type test shall be remedied before further testing of a valve.
One thyristor level is permitted to fail due to short-circuiting in any type test. If, following a
type test, one thyristor level has become short-circuited, then the failed level shall be restored
and this type test repeated (see 4.4.2 b) in IEC 60700-1:2015). The total number of thyristor
levels allowed to fail during all tests are given in Table 2.
The distribution of short-circuited levels and of other thyristor level faults at the end of all type
tests shall be essentially random and it shall not show any pattern indicative of inadequate
design.
4.6 Documentation of test results
4.6.1 Test reports to be issued
The supplier shall provide certified test reports of all type tests performed on the valves or
valve sections.
Test records on the results of routine tests shall be provided by the supplier.
Table 2 – Number of thyristor levels permitted to fail during type tests
Number of thyristor Number of thyristor Total number of Additional number
levels in a complete levels permitted to thyristor levels of thyristor levels,
valve fail to short circuit permitted to fail to in all type tests,
in any one type test short circuit in all permitted to have
type tests experienced a fault
but have not
become short
circuited
<34 1 2 2
34 ≤ n < 68 1 3 3
1 4 4
68 ≤ n < 101
4.6.2 Contents of a type test report
A report on the type tests conducted on the thyristor valves shall be produced. The report
shall include the following:
a) general data such as:
– identification of the equipment tested (e.g. type and ratings, drawing number, serial
number, etc.);
– identification of major parts of the test objects (e.g. thyristors, valve reactors, printed
circuit cards, etc.);
– name and location of the facility where the test was carried out;
– relevant circumstances wherever necessary (e.g. temperature, humidity and
barometric pressure during the dielectric tests, etc.);
– reference to the test specification;
– dates of the tests;
– name(s) and signature(s) of the personnel responsible;
– signature of the purchaser's inspector (if present) and the sign of his approval (if
required);
b) description of power sources (i.e. impulse voltage generator, DC voltage source, etc.)
used for the particular test, such as the name of the manufacturer, ratings, characteristics,
etc.;
c) description of the measuring instrumentation, including information on guaranteed
accuracy and date of the last calibration;
d) detailed information on the arrangement for each test (e.g. circuit diagram);
e) description of the test procedures;
f) any agreed deviations or waivers;
g) tabulated results including photographs, oscillograms, graphs, etc.;
h) reports on component failures or other unusual events;
i) conclusions and recommendations, if any.
– 16 – IEC 61954:2021 RLV © IEC 2021
5 Type tests on TCR and TSR valves
5.1 Dielectric tests between valve terminals and earth
5.1.1 General
For these tests, each thyristor valve shall be short-circuited across valve terminals or
individual thyristor levels.
For valves belonging to an MVU, all valves in the same structure shall be short-circuited and
connected together. The test voltage shall be applied between all the valves and earth.
See 4.4.1.1 for other detailed requirements of the test object.
5.1.2 AC test
5.1.2.1 Objectives
See 4.2.2.2.
5.1.2.2 Test values and waveshapes
U and U have sinusoidal waveshapes with a frequency of 50 Hz or 60 Hz, depending on
ts1 ts2
the test facilities. U is chosen as the standard short-duration power-frequency withstand
ts1
voltage according to IEC 60071-1:201
...
IEC 61954 ®
Edition 3.0 2021-10
INTERNATIONAL
STANDARD
NORME
INTERNATIONALE
Static VAR compensators (SVC) – Testing of thyristor valves
Compensateurs statiques de puissance réactive (SVC) – Essais des valves à
thyristors
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IEC 61954 ®
Edition 3.0 2021-10
INTERNATIONAL
STANDARD
NORME
INTERNATIONALE
Static VAR compensators (SVC) – Testing of thyristor valves
Compensateurs statiques de puissance réactive (SVC) – Essais des valves à
thyristors
INTERNATIONAL
ELECTROTECHNICAL
COMMISSION
COMMISSION
ELECTROTECHNIQUE
INTERNATIONALE
ICS 29.240.99; 31.080.20 ISBN 978-2-8322-1033-1
– 2 – IEC 61954:2021 © IEC 2021
CONTENTS
FOREWORD . 5
1 Scope . 7
2 Normative references. 7
3 Terms and definitions . 7
4 General requirements for type, production and optional tests . 9
4.1 Summary of tests . 9
4.2 Objectives of tests . 10
4.2.1 General . 10
4.2.2 Dielectric tests . 10
4.2.3 Operational tests . 10
4.2.4 Electromagnetic interference tests . 11
4.2.5 Production tests . 11
4.2.6 Optional tests. 11
4.3 Guidelines for the performance of type and optional tests . 11
4.4 Test conditions . 12
4.4.1 General . 12
4.4.2 Valve temperature at testing . 13
4.4.3 Redundant thyristor levels . 13
4.5 Permissible component failures during type testing . 14
4.6 Documentation of test results . 14
4.6.1 Test reports to be issued . 14
4.6.2 Contents of a type test report . 15
5 Type tests on TCR and TSR valves . 15
5.1 Dielectric tests between valve terminals and earth . 15
5.1.1 General . 15
5.1.2 AC test . 16
5.1.3 Lightning impulse test . 16
5.2 Dielectric tests between valves (MVU only) . 17
5.2.1 General . 17
5.2.2 AC test . 17
5.2.3 Lightning impulse test . 18
5.3 Dielectric tests between valve terminals . 18
5.3.1 General . 18
5.3.2 AC test . 18
5.3.3 Switching impulse test . 20
5.4 Operational tests . 21
5.4.1 Periodic firing and extinction test . 21
5.4.2 Minimum AC voltage test . 22
5.4.3 Temperature rise test . 23
6 Type tests on TSC valves . 23
6.1 Dielectric tests between valve terminals and earth . 23
6.1.1 General . 23
6.1.2 AC-DC test . 24
6.1.3 Lightning impulse test . 25
6.2 Dielectric tests between valves (for MVU only) . 26
6.2.1 General . 26
6.2.2 AC-DC test . 26
6.2.3 Lightning impulse test . 28
6.3 Dielectric tests between valve terminals . 28
6.3.1 General . 28
6.3.2 AC-DC test . 28
6.3.3 Switching impulse test . 30
6.4 Operational tests . 31
6.4.1 Overcurrent tests . 31
6.4.2 Minimum AC voltage test . 35
6.4.3 Temperature rise test . 36
7 Electromagnetic interference tests . 36
7.1 Objectives . 36
7.2 Test procedures . 36
7.2.1 General . 36
7.2.2 Switching impulse test . 37
7.2.3 Non-periodic firing test . 37
8 Production tests . 37
8.1 General . 37
8.2 Visual inspection . 37
8.3 Connection check . 37
8.4 Voltage-dividing/damping circuit check . 38
8.5 Voltage withstand check . 38
8.6 Check of auxiliaries . 38
8.7 Firing check . 38
8.8 Cooling system pressure test . 38
8.9 Partial discharge tests . 38
9 Optional tests on TCR and TSR valves . 38
9.1 Overcurrent test . 38
9.1.1 Overcurrent with subsequent blocking . 38
9.1.2 Overcurrent without blocking . 39
9.2 Positive voltage transient during recovery test . 39
9.2.1 Objectives . 39
9.2.2 Test values and waveshapes . 39
9.2.3 Test procedures . 40
9.3 Non-periodic firing test . 40
9.3.1 Objectives . 40
9.3.2 Test values and waveshapes . 40
9.3.3 Test procedures . 41
10 Optional tests on TSC valves . 42
10.1 Positive voltage transient during recovery test . 42
10.1.1 Test objective . 42
10.1.2 Test values and waveshapes . 42
10.1.3 Test procedures . 42
10.2 Non-periodic firing test . 42
10.2.1 Objectives . 42
10.2.2 Test values and waveshapes . 43
10.2.3 Test procedures . 44
– 4 – IEC 61954:2021 © IEC 2021
Figure 1 – TSC branch . 33
Figure 2 – One-loop overcurrent . 34
Figure 3 – Two-loop overcurrent . 35
Table 1 – List of tests . 9
Table 2 – Number of thyristor levels permitted to fail during type tests . 15
INTERNATIONAL ELECTROTECHNICAL COMMISSION
____________
STATIC VAR COMPENSATORS (SVC) –
TESTING OF THYRISTOR VALVES
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
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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
assessment services and, in some areas, access to IEC marks of conformity. IEC is not responsible for any
services carried out by independent certification bodies.
6) All users should ensure that they have the latest edition of this publication.
7) No liability shall attach to IEC or its directors, employees, servants or agents including individual experts and
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other damage of any nature whatsoever, whether direct or indirect, or for costs (including legal fees) and
expenses arising out of the publication, use of, or reliance upon, this IEC Publication or any other IEC
Publications.
8) Attention is drawn to the Normative references cited in this publication. Use of the referenced publications is
indispensable for the correct application of this publication.
9) Attention is drawn to the possibility that some of the elements of this IEC Publication may be the subject of
patent rights. IEC shall not be held responsible for identifying any or all such patent rights.
International Standard IEC 61954 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 third edition cancels and replaces the second edition published in 2011,
Amendment 1:2013 and Amendment 2:2017. This edition constitutes a technical revision.
This edition includes the following significant technical changes with respect to the previous
edition: important clarifications were made in 4.4.1.2, 5.1.2.2, 5.1.3.2, 5.2.3.2, 6.1.2.2,
6.1.2.4, 6.1.3.2, 6.2.2.2, 6.2.2.4, 6.3.2.2 and 9.3.2.
– 6 – IEC 61954:2021 © IEC 2021
The text of this International Standard is based on the following documents:
FDIS Report on voting
22F/642/FDIS 22F/658/RVD
Full information on the voting for the approval of this International Standard can be found in
the report on voting indicated in the above table.
The language used for the development of this International Standard is English.
This document was drafted in accordance with ISO/IEC Directives, Part 2, and developed in
accordance with ISO/IEC Directives, Part 1 and ISO/IEC Directives, IEC Supplement,
available at www.iec.ch/members_experts/refdocs. The main document types developed by
IEC are described in greater detail at www.iec.ch/standardsdev/publications.
The committee has decided that the contents of this document will remain unchanged until the
stability date indicated on the IEC website under "http://webstore.iec.ch" in the data related to
the specific document. At this date, the document will be
• reconfirmed,
• withdrawn,
• replaced by a revised edition, or
• amended.
STATIC VAR COMPENSATORS (SVC) –
TESTING OF THYRISTOR VALVES
1 Scope
This document defines type, production and optional tests on thyristor valves used in thyristor
controlled reactors (TCR), thyristor switched reactors (TSR) and thyristor switched capacitors
(TSC) forming part of static VAR compensators (SVC) for power system applications. The
requirements of the document apply both to single valve units (one phase) and to multiple
valve units (several phases).
Clauses 4 to 7 detail the type tests, i.e. tests which are carried out to verify that the valve
design meets the requirements specified. Clause 8 covers the production tests, i.e. tests
which are carried out to verify proper manufacturing. Clauses 9 and 10 detail optional tests,
i.e. tests additional to the type and production tests.
2 Normative references
The following documents are referred to in the text in such a way that some or all of their
content constitutes requirements of this document. For dated references, only the edition
cited applies. For undated references, the latest edition of the referenced document (including
any amendments) applies.
IEC 60060 (all parts), High-voltage test techniques
IEC 60060-1:2010, High-voltage test techniques – Part 1: General definitions and test
requirements
IEC 60060-2, High-voltage test techniques – Part 2: Measuring systems
IEC 60071 (all parts), Insulation co-ordination
IEC 60071-1:2019, Insulation co-ordination – Part 1: Definitions, principles and rules
IEC 60270, High-voltage test techniques – Partial discharge measurements
IEC 60700-1:2015, Thyristor valves for high-voltage direct current (HVDC) power transmission
– Part 1: Electrical testing
3 Terms and definitions
For the purposes of this document, the following terms and definitions apply.
ISO and IEC maintain terminological databases for use in standardization at the following
addresses:
• IEC Electropedia: available at http://www.electropedia.org/
• ISO Online browsing platform: available at http://www.iso.org/obp
– 8 – IEC 61954:2021 © IEC 2021
3.1
thyristor level
part of a thyristor valve comprising a thyristor, or thyristors connected in parallel or anti-
parallel, together with their immediate auxiliaries and reactor, if any
3.2
thyristor (series) string
series connected thyristors forming one direction of a thyristor valve
3.3
valve reactor
reactor incorporated within some valves for limitation of stresses
Note 1 to entry: For testing purposes it is considered an integral part of the valve.
3.4
valve section
electrical assembly, comprising a number of thyristors and other components, which exhibits
pro-rated electrical properties of a complete thyristor valve, but only a portion of the full
voltage blocking capability of the thyristor valve, and which can be used for tests
3.5
thyristor valve
electrically and mechanically combined assembly of thyristor levels, complete with all
connections, auxiliary components and mechanical structures, which can be connected in
series with each phase of the reactor or capacitor of an SVC
3.6
valve structure
physical structure which insulates the valves to the appropriate level above earth potential
and from each other
3.7
valve base electronics
VBE
electronic unit, at earth potential, which is the interface between the control system of the
SVC and the thyristor valves
3.8
multiple valve unit
MVU
assembly of several valves in the same physical structure which cannot be separated for test
purposes (e.g. three-phase valves)
3.9
redundant thyristor levels
maximum number of thyristor levels in the thyristor valve that may be short-circuited,
externally or internally, during service without affecting the safe operation of the thyristor
valve as demonstrated by type tests; and which if and when exceeded, would require either
the shutdown of the thyristor valve to replace the failed thyristors, or the acceptance of
increased risk of failures
3.10
voltage breakover (VBO) protection
means of protecting the thyristors from excessive voltage by firing them at a predetermined
voltage
4 General requirements for type, production and optional tests
4.1 Summary of tests
Table 1 lists the tests given in the following clauses and subclauses.
Table 1 – List of tests
Test Subclause Test object
TCR/TSR TSC
Dielectric tests between valve terminals and earth (type tests)
AC test 5.1.2 Valve
AC-DC test 6.1.2 Valve
Lightning impulse test 5.1.3 6.1.3 Valve
Dielectric tests between valves (MVU only) (type tests)
AC test 5.2.2 MVU
AC-DC test 6.2.2 MVU
Lightning impulse test 5.2.3 6.2.3 MVU
Dielectric tests between valve terminals (type tests)
AC test 5.3.2 Valve
AC-DC test 6.3.2 Valve
Switching impulse test 5.3.3 6.3.3 Valve
Operational tests (type tests)
Periodic firing and extinction test 5.4.1 Valve or valve section
Overcurrent test 6.4.1 Valve or valve section
Minimum AC voltage test 5.4.2 6.4.2 Valve or valve section
Temperature rise test 5.4.3 6.4.3 Valve or valve section
Electromagnetic interference tests (type tests)
Switching impulse test 7.2.2 7.2.2 Valve
Non-periodic firing test 7.2.3 7.2.3 Valve
Production tests
Visual inspection 8.2 8.2
Connection check 8.3 8.3
Voltage dividing/damping circuit check 8.4 8.4
Voltage withstand check 8.5 8.5
Check of auxiliaries 8.6 8.6
Firing check 8.7 8.7
Cooling system pressure test 8.8 8.8
Partial discharge tests 8.9 8.9
Optional tests
Overcurrent test 9.1 Valve or valve section
Positive voltage transient during recovery test 9.2 10.1 Valve or valve section
Non-periodic firing test 9.3 10.2 Valve or valve section
– 10 – IEC 61954:2021 © IEC 2021
4.2 Objectives of tests
4.2.1 General
The tests described apply to the valve (or valve sections), the valve structure and those parts
of the coolant distribution system and firing and monitoring circuits which are contained within
the valve structure or connected between the valve structure and earth. Other equipment,
such as valve control and protection and valve base electronics may be essential for
demonstrating the correct function of the valve during the tests but are not in themselves the
subject of the tests.
4.2.2 Dielectric tests
4.2.2.1 General
Tests for the following dielectric stresses are specified:
– AC voltage;
– combined AC and DC voltage (TSC only);
– impulse voltages.
In the interest of standardization with other equipment, lightning impulse tests between valve
terminals and earth and between phases of an MVU are included. For tests between valve
terminals, the only impulse test specified is a switching impulse.
4.2.2.2 Tests on valve structure
Tests are defined for the voltage withstand requirements between a valve (with its terminals
short-circuited) and earth, and also between valves for MVU. The tests shall demonstrate
that:
– sufficient clearances have been provided to prevent flashovers;
– there is no disruptive discharge in the insulation of the valve structure, cooling ducts, light
guides and other insulation parts of the pulse transmission and distribution systems;
– partial discharge inception and extinction voltages under AC and DC conditions are above
the maximum steady-state operating voltage appearing on the valve structure.
4.2.2.3 Tests between valve terminals
The purpose of these tests is to verify the design of the valve with respect to its capability to
withstand overvoltages between its terminals. The tests shall demonstrate that:
– sufficient internal insulation has been provided to enable the valve to withstand specified
voltages;
– partial discharge inception and extinction voltages under AC and DC conditions are above
the maximum steady-state operating voltage appearing between valve terminals;
– the protective overvoltage firing system (if provided) works as intended;
– the thyristors have adequate du/dt capability for in-service conditions. (In most cases the
specified tests are sufficient; however, in some exceptional cases additional tests may be
required.)
4.2.3 Operational tests
The purpose of these tests is to verify the valve design for combined voltage and current
stresses under normal and abnormal repetitive conditions as well as under transient fault
conditions. They shall demonstrate that, under specified conditions:
– the valve functions properly;
– the turn-on and turn-off voltage and current stresses are within the capabilities of the
thyristors and other internal circuits;
– the cooling provided is adequate and no component is overheated;
– the overcurrent withstand capability of the valve is adequate.
4.2.4 Electromagnetic interference tests
The principal objective of these tests is to demonstrate the immunity of the valve to
electromagnetic interference from within the valve and from outside the valve. Generally,
immunity to electromagnetic interference is demonstrated by monitoring of the valve during
other tests.
4.2.5 Production tests
The objective of tests is to verify proper manufacture. The production tests shall demonstrate
that:
– all materials, components and sub-assemblies used in the valve have been correctly
installed;
– the valve equipment functions as intended, and predefined parameters are within
prescribed acceptance limits;
– thyristor levels and valve or valve sections have the necessary voltage withstand
capability;
– consistency and uniformity in production is achieved.
4.2.6 Optional tests
Optional tests are additional tests which may be performed, subject to agreement between the
purchaser and the supplier. The objectives are the same as for the operational tests specified
in 4.2.3. The test object is normally one valve or appropriate equivalent number of valve
sections.
4.3 Guidelines for the performance of type and optional tests
The following principles shall apply:
– type tests shall be performed on at least one valve or on an appropriate number of valve
sections, as indicated in Table 1 (see 4.1), to verify that the valve design meets the
specified requirements. All type tests shall be performed on the same valve(s) or valve
section(s);
– provided that the valve is demonstrably similar to one previously tested, the supplier may
submit a certified report of any previous type test, at least equal to the requirements
specified in the contract, in lieu of the type test;
– for type tests performed on valve sections, the total number of thyristor levels subjected to
such type tests shall be at least equal to the number of thyristor levels in a valve;
– the valve or valve sections used for type tests shall first pass all production tests. On
completion of the type test programme, the valve or valve sections shall be checked again
for compliance with the production test criteria;
– material for the type tests shall be selected at random;
– the dielectric tests shall be performed in accordance with IEC 60060-1 and IEC 60060-2
where applicable;
– individual tests may be performed in any order.
NOTE Tests involving partial discharge measurement may provide added confidence if performed at the end of
the dielectric type test programme.
– 12 – IEC 61954:2021 © IEC 2021
4.4 Test conditions
4.4.1 General
4.4.1.1 Dielectric test objects
Dielectric tests shall be performed on completely assembled valves, whereas some
operational tests may be performed on either complete valves or valve sections.
The valve shall be assembled with all auxiliary components except for the valve arrester, if
used. Unless otherwise specified, the valve electronics shall be energized. The cooling and
insulating fluids in particular shall be in a condition that represents service conditions such as
conductivity, except for the flow rate and anti-freezing media content, which can be reduced.
If any object or device external to the structure is necessary for proper representation of the
stresses during the test, it shall also be present or simulated in the test. Metallic parts of the
valve structure (or other valves in an MVU) which are not part of the test shall be shorted
together and connected to earth in a manner appropriate to the test in question.
4.4.1.2 Atmospheric correction
Atmospheric correction shall be applied to the test voltages in accordance with IEC 60060-1,
except when specifically excluded. To calculate the test values applicable at standard
reference atmosphere, the methods described in IEC 60060-1:2010,4.3.3.1 shall be used,
considering the following conditions as input values for pressure p, temperature t and
humidity h:
– pressure:
If the insulation coordination of the tested part of the thyristor valve is based on standard
rated withstand voltages according to IEC 60071-1, correction factors are only applied for
altitudes exceeding 1 000 m. Hence if the altitude of the site a at which the equipment will
s
be installed is less than 1 000 m, then the standard atmospheric air pressure (b = 101,3
kPa) shall be used with no correction for altitude. If a >1 000 m, then the standard
s
procedure according to IEC 60060-1 is used except that the reference atmospheric
pressure b is replaced by the atmospheric pressure corresponding to an altitude of
1 000 m (b ).
1 000 m
If the insulation coordination of the tested part of the thyristor valve is not based on
standard rated withstand voltages according to IEC 60071-1, then the standard procedure
according to IEC 60060-1 is used with the reference atmospheric pressure b
(b = 101,3 kPa).
– temperature:
design maximum valve hall air temperature (°C).
– humidity:
design minimum valve hall absolute humidity (g/m ).
The values to be used shall be specified by the supplier.
In any of the afore mentioned cases, the correction of test values from standard reference
atmosphere to test conditions shall be as per IEC 60060-1:2010,4.3.3.2.
Where non-standard test levels are defined by this document, a site air density correction
factor k , defined below shall be applied where stated.
d
The value of k shall be determined from the following formula:
d
b 273+ T
1 2
k = ×
(1)
d
b 273+ T
2 1
where
b is the laboratory ambient air pressure, in pascals (Pa);
T is the laboratory ambient air temperature, in degrees Celsius (°C);
b is the standard reference atmosphere of 101,3 kPa (i.e. 1 013 mbar), corrected to the
altitude of the site at which the equipment will be installed;
T is the design maximum valve hall air temperature, in degrees Celsius (°C).
Correction factors shall not be applied to the dielectric tests between valve terminals or to the
long duration dielectric tests whose primary purpose is to check for the internal insulation and
partial discharges.
The atmospheric correction factors shall not be applied to operational tests or optional tests.
4.4.1.3 Operational tests
Where possible, a complete thyristor valve should be tested. Otherwise the tests may be
performed on thyristor valve sections. The choice depends mainly upon the thyristor valve
design and the test facilities available. Where tests on the thyristor valve sections are
proposed, the tests specified in this standard are valid for thyristor valve sections containing
five or more series-connected thyristor levels. If tests on thyristor valve sections with fewer
than five thyristor levels are proposed, additional test safety factors shall be agreed upon.
Under no circumstances shall the number of series-connected thyristor levels in a thyristor
valve section be less than three.
Sometimes, operational tests may be performed at a power frequency different from the
service frequency, e.g. 50 Hz instead of 60 Hz. Some operational stresses such as switching
losses or I t of short-circuit current are affected by the actual power frequency during tests.
When this situation occurs, the test conditions shall be reviewed, and appropriate changes
made to ensure that the valve stresses are at least as severe as they would be if the tests
were performed at the service frequency.
The coolant shall be in a condition representative of service conditions. Flow and
temperature, in particular, shall be set to the most unfavourable values appropriate to the test
in question. Anti-freezing media content should, preferably, be equivalent to the service
condition; however, where this is not practicable, a correction factor agreed between the
supplier and the purchaser shall be applied.
4.4.2 Valve temperature at testing
4.4.2.1 Valve temperature for dielectric tests
Unless specified otherwise, tests shall be performed at room temperature.
4.4.2.2 Valve temperature for operational tests
Unless specified otherwise, tests shall be carried out under the conditions that produce the
highest component temperature that may occur in real operation.
If several components are to be verified by a test, it may be necessary to carry out the same
test under different conditions.
4.4.3 Redundant thyristor levels
4.4.3.1 Dielectric tests
All dielectric tests on a complete valve shall be carried out with redundant thyristor levels
short-circuited, except where otherwise indicated.
– 14 – IEC 61954:2021 © IEC 2021
4.4.3.2 Operational tests
For operational tests, redundant thyristor levels should not be short-circuited. The test
voltages and circuit impedances used shall be adjusted by means of a scaling factor k .
n
N
tot
k = (2)
n
N − N
t r
where
N is the total number of series thyristor levels in the test object;
tot
N is the total number of series thyristor levels in the valve;
t
N is the total number of redundant series thyristor levels in the valve.
r
NOTE In thyristor valves with a small number of thyristor levels, where the redundancy is a significant portion of
the total, this may cause certain valve components to be overstressed. As an alternative, it is therefore acceptable
to perform the operational test with redundant thyristor levels short-circuited and without scaling the test voltages
and impedances by k .
n
4.5 Permissible component failures during type testing
Experience in industry shows that, even with the most careful design of valves, it is not
possible to avoid occasional random failures of thyristor level components during service
operation. Even though these failures may be stress-related, they are considered random to
the extent that the cause of failure or the relationship between failure rate and stress cannot
be predicted or is not amenable to precise quantitative definition. Type tests subject valves or
valve sections, within a short time, to multiple stresses that generally correspond to the worst
stresses that can be experienced by the equipment not more than a few times during the life
of the valve. Considering the above, the criteria for successful type testing set out below
therefore permit a small number of thyristor levels to fail during type testing, providing that the
failures are essentially random and do not show any pattern that is indicative of inadequate
design.
The valves or valve sections shall be checked before each test, after any preliminary
calibration tests, and again after each type test to determine whether any thyristors or
auxiliary components have failed during the test. Failed thyristors or auxiliary components
found at the end of a type test shall be remedied before further testing of a valve.
One thyristor level is permitted to fail due to short-circuiting in any type test. If, following a
type test, one thyristor level has become short-circuited, then the failed level shall be restored
and this type test repeated (see 4.4.2 b) in IEC 60700-1:2015). The total number of thyristor
levels allowed to fail during all tests are given in Table 2.
The distribution of short-circuited levels and of other thyristor level faults at the end of all type
tests shall be essentially random and it shall not show any pattern indicative of inadequate
design.
4.6 Documentation of test results
4.6.1 Test reports to be issued
The supplier shall provide certified test reports of all type tests performed on the valves or
valve sections.
Test records on the results of routine tests shall be provided by the supplier.
Table 2 – Number of thyristor levels permitted to fail during type tests
Number of thyristor Number of thyristor Total number of Additional number
levels in a complete levels permitted to thyristor levels of thyristor levels,
valve fail to short circuit permitted to fail to in all type tests,
in any one type test short circuit in all permitted to have
type tests experienced a fault
but have not
become short
circuited
1 2 2
<34
1 3 3
34 ≤ n < 68
68 ≤ n < 101 1 4 4
4.6.2 Contents of a type test report
A report on the type tests conducted on the thyristor valves shall be produced. The report
shall include the following:
a) general data such as:
– identification of the equipment tested (e.g. type and ratings, drawing number, serial
number, etc.);
– identification of major parts of the test objects (e.g. thyristors, valve reactors, printed
circuit cards, etc.);
– name and location of the facility where the test was carried out;
– relevant circumstances wherever ne
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