IEC 62501:2024

IEC 62501 ®
Edition 2.0 2024-04
COMMENTED VERSION
INTERNATIONAL
STANDARD
colour
inside
Voltage sourced converter (VSC) valves for high-voltage direct current (HVDC)
power transmission – Electrical testing
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IEC 62501 ®
Edition 2.0 2024-04
COMMENTED VERSION
INTERNATIONAL
STANDARD
colour
inside
Voltage sourced converter (VSC) valves for high-voltage direct current (HVDC)
power transmission – Electrical testing
INTERNATIONAL
ELECTROTECHNICAL
COMMISSION
ICS 29.200, 29.240.99 ISBN 978-2-8322-8751-4
– 2 – IEC 62501:2024 CMV © IEC 2024
CONTENTS
FOREWORD .5
1 Scope .7
2 Normative references .7
3 Terms and definitions .7
3.1 Insulation coordination terms .8
3.2 Power semiconductor terms .8
3.3 Operating states of converter .8
3.4 VSC construction terms .9
3.5 Valve structure terms . 10
4 General requirements . 11
4.1 Guidelines for the performance of type tests . 11
4.1.1 Evidence in lieu . 11
4.1.2 Selection of test object . 12
4.1.3 Test procedure . 12
4.1.4 Ambient temperature for testing . 12
4.1.5 Frequency for testing . 12
4.1.6 Test reports . 12
4.1.7 Conditions to be considered in determination of type test parameters . 13
4.2 Atmospheric correction factor . 13
4.3 Treatment of redundancy . 13
4.3.1 Operational tests . 13
4.3.2 Dielectric tests . 13
4.4 Criteria for successful type testing. 14
4.4.1 General . 14
4.4.2 Criteria applicable to valve levels . 14
4.4.3 Criteria applicable to the valve as a whole . 15
5 List of type tests. 15
6 Operational tests . 16
6.1 Purpose of tests . 16
6.2 Test object . 16
6.3 Test circuit . 17
6.4 Maximum continuous operating duty test . 17
6.5 Maximum temporary over-load operating duty test . 18
6.6 Minimum DC voltage test . 18
7 Dielectric tests on valve support structure . 19
7.1 Purpose of tests . 19
7.2 Test object . 19
7.3 Test requirements . 20
7.3.1 General . 20
7.3.2 Valve support DC voltage test . 20
7.3.3 Valve support AC voltage test . 21
7.3.4 Valve support switching impulse test . 21
7.3.5 Valve support lightning impulse test . 22
8 Dielectric tests on multiple valve unit . 22
8.1 General . 22
8.2 Purpose of tests . 22

8.3 Test object . 22
8.4 Test requirements . 22
8.4.1 MVU DC voltage test to earth . 22
8.4.2 MVU AC voltage test . 23
8.4.3 MVU switching impulse test . 24
8.4.4 MVU lightning impulse test. 25
9 Dielectric tests between valve terminals . 26
9.1 Purpose of the test . 26
9.2 Test object . 26
9.3 Test methods . 27
9.3.1 General . 27
9.3.2 Method one . 27
9.3.3 Method two . 28
9.4 Test requirements . 28
9.4.1 Valve Composite AC-DC voltage test . 28
9.4.2 Alternative tests (Method 2 only) . 31
9.4.3 Valve impulse tests (general) . 32
10 IGBT overcurrent turn-off test . 34
10.1 Purpose of test . 34
10.2 Test object . 34
10.3 Test requirements . 34
11 Short-circuit current test . 35
11.1 Purpose of tests . 35
11.2 Test object . 36
11.3 Test requirements . 36
12 Tests for valve insensitivity to electromagnetic disturbance . 36
12.1 Purpose of tests . 36
12.2 Test object . 37
12.3 Test requirements . 37
12.3.1 General . 37
12.3.2 Approach one . 37
12.3.3 Approach two . 37
12.3.4 Acceptance criteria . 37
13 Tests for dynamic braking valves . 38
14 Production tests . 38
14.1 General . 38
14.2 Purpose of tests . 38
14.3 Test object . 38
14.4 Test requirements . 39
14.5 Production test objectives . 39
14.5.1 Visual inspection . 39
14.5.2 Connection check . 39
14.5.3 Voltage-grading circuit check . 39
14.5.4 Control, protection and monitoring circuit checks . 39
14.5.5 Voltage withstand check . 39
13.4.6 Partial discharge tests .
14.5.6 Turn-on / turn-off check . 40
14.5.7 Pressure test . 40

– 4 – IEC 62501:2024 CMV © IEC 2024
15 Presentation of type test results . 40
Annex A (informative) Overview of VSC converters in HVDC power transmission . 41
A.1 General . 41
A.2 VSC basics. 41
A.3 Overview of main types of VSC valve . 43
A.4 Switch type VSC valve . 43
A.4.1 General . 43
A.4.2 2-level converter. 44
A.4.3 Multi-level diode clamped converter . 44
A.4.4 Multi-level flying capacitor converter . 45
A.5 Controllable voltage source type VSC valve. 46
A.5.1 General . 46
A.5.2 Modular multi-level converter (MMC) . 47
A.5.3 Cascaded two-level converter (CTL). 49
A.5.4 Terminology for valves of the controllable voltage source type . 50
A.6 Hybrid VSC valves . 52
A.7 Main differences between VSC and conventional HVDC valves . 52
Annex B (informative) Valve component fault tolerance . 53
Annex C (informative) Valve losses determination . 55
Bibliography . 56
List of comments . 57

Figure A.1 – A single VSC phase unit and its idealized output voltage . 42
Figure A.2 – Output voltage of a VSC phase unit for a 2-level converter. 42
Figure A.3 – Output voltage of a VSC phase unit for a 15-level converter, without PWM . 43
Figure A.4 – Basic circuit topology of one phase unit of a 2-level converter . 44
Figure A.5 – Basic circuit topology of one phase unit of a 3-level diode-clamped
converter . 45
Figure A.6 – Basic circuit topology of one phase unit of a 5-level diode-clamped
converter . 45
Figure A.7 – Basic circuit topology of one phase unit of a 3-level flying capacitor
converter . 46
Figure A.8 – A single VSC phase unit with controllable voltage source type VSC valves . 47
Figure A.9 – The half-bridge MMC circuit . 48
Figure A.10 – The full-bridge MMC circuit . 48
Figure A.11 – The half-bridge CTL circuit . 50
Figure A.12 – Construction terms in MMC valves . 51
Figure A.13 – Construction terms in CTL valves . 51

Table 1 – Conditions for use of evidence in lieu from another HVDC project . 11
Table 2 – Minimum number of valve levels to be operational type tested as a function
of the number of valve levels per valve . 12
Table 3 – Valve level faults permitted during type tests . 15
Table 4 – List of type tests . 16

INTERNATIONAL ELECTROTECHNICAL COMMISSION
____________
VOLTAGE SOURCED CONVERTER (VSC)
VALVES FOR HIGH-VOLTAGE DIRECT CURRENT (HVDC)
POWER TRANSMISSION – ELECTRICAL TESTING
FOREWORD
1) The International Electrotechnical Commission (IEC) is a worldwide organization for standardization comprising
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shall not be held responsible for identifying any or all such patent rights.
This commented version (CMV) of the official standard IEC 62501:2024 edition 2.0 allows
the user to identify the changes made to the previous IEC 62501:2009+AMD1:2014
+AMD2:2017 CSV edition 1.2. Furthermore, comments from IEC SC 22F experts are
provided to explain the reasons of the most relevant changes, or to clarify any part of
the content.
A vertical bar appears in the margin wherever a change has been made. Additions are in
green text, deletions are in strikethrough red text. Experts' comments are identified by a
blue-background number. Mouse over a number to display a pop-up note with the
comment.
This publication contains the CMV and the official standard. The full list of comments is
available at the end of the CMV.

– 6 – IEC 62501:2024 CMV © IEC 2024
IEC 62501 has been prepared by subcommittee 22F: Power electronics for electrical
transmission and distribution systems, of IEC technical committee 22: Power electronic systems
and equipment. It is an International Standard.
This second edition cancels and replaces the first edition published in 2009, Amendment 1:2014
and Amendment 2:2017. This edition constitutes a technical revision.
This edition includes the following significant technical changes with respect to the previous
edition:
a) Conditions for use of evidence in lieu are inserted as a new Table 1;
b) Test parameters for valve support DC voltage test, 7.3.2, and MVU DC voltage test, 8.4.1,
updated;
c) AC-DC voltage test between valve terminals, Clause 9, is restructured and alternative tests,
by individual AC and DC voltage tests, added in 9.4.2;
d) Partial discharge test in routine test program is removed;
e) More information on valve component fault tolerance, Annex B, is added;
f) Valve losses determination is added as Annex C.
The text of this International Standard is based on the following documents:
Draft Report on voting
22F/731/CDV 22F/748A/RVC
Full information on the voting for its approval can be found in the report on voting indicated in
the above table.
The language used for the development of this International Standard is English.
This document was drafted in accordance with ISO/IEC Directives, Part 2, and developed in
accordance with ISO/IEC Directives, Part 1 and ISO/IEC Directives, IEC Supplement, available
at www.iec.ch/members_experts/refdocs. The main document types developed by IEC are
described in greater detail at www.iec.ch/publications.
The committee has decided that the contents of this document will remain unchanged until the
stability date indicated on the IEC website under webstore.iec.ch in the data related to the
specific document. At this date, the document will be
• reconfirmed,
• withdrawn, or
• revised.
IMPORTANT – The "colour inside" logo on the cover page of this document 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.

VOLTAGE SOURCED CONVERTER (VSC)
VALVES FOR HIGH-VOLTAGE DIRECT CURRENT (HVDC)
POWER TRANSMISSION – ELECTRICAL TESTING

1 Scope
This International Standard applies to self-commutated converter valves, for use in a three-
phase bridge voltage sourced converter (VSC) for high voltage DC power transmission or as
part of a back-to-back link, and to dynamic braking valves. It is restricted to electrical type and
production tests.
The scope of this standard includes the electrical type and production tests of dynamic braking
valves which may be used in some HVDC schemes for d.c. overvoltage limitation.
This document can be used as a guide for testing of high-voltage VSC valves used in energy
storage systems (ESS). 1
The tests specified in this document are based on air insulated valves. For other types of valves,
The test requirements and acceptance criteria should be agreed between the purchaser and
the supplier. The test requirements and acceptance criteria can be used for guidance to specify
the electrical type and production tests of other types of valves.
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 60071 (all parts), Insulation co-ordination
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
IEC 60700-1:2015/AMD1:2021
IEC 62747, Terminology for voltage-sourced converters (VSC) for high-voltage direct current
(HVDC) systems
ISO/IEC 17025, General requirements for the competence of testing and calibration
laboratories
3 Terms and definitions
For the purposes of this document, the terms and definitions given in IEC 62747 and the
following apply.
ISO and IEC maintain terminology databases for use in standardization at the following
addresses:
– 8 – IEC 62501:2024 CMV © IEC 2024
• IEC Electropedia: available at https://www.electropedia.org/
• ISO Online browsing platform: available at https://www.iso.org/obp
3.1 Insulation coordination terms
3.1.1
test withstand voltage
value of a test voltage of standard waveshape at which a new valve, with unimpaired integrity,
does not show any disruptive discharge and meets all other acceptance criteria specified for
the particular test, when subjected to a specified number of applications or a specified duration
of the test voltage, under specified conditions
3.1.2
internal insulation
air external to the components and insulating materials of the valve, but contained within the
profile of the valve or multiple valve unit
3.1.3
external insulation
air between the external surface of the valve or multiple valve unit and its surroundings
3.2 Power semiconductor terms
3.2.1
turn-off semiconductor device
controllable semiconductor device which may be turned on and off by a control signal, for
example an IGBT
Note 1 to entry: There are several types of turn-off semiconductor devices which can be used in VSC converters
for HVDC. For convenience, the term IGBT is used throughout this standard to refer to the main turn-off
semiconductor device. However, the standard is equally applicable to other types of turn-off semiconductor devices.
3.2.2
insulated gate bipolar transistor IGBT
turn-off semiconductor device with three terminals: a gate terminal (G) and two load terminals
emitter (E) and collector (C)
Note 1 to entry: By applying appropriate gate to emitter voltages, the load current can be controlled, i.e. turned on
and turned off.
3.2.3
free-wheeling diode
FWD
power semiconductor device with diode characteristic
Note 1 to entry: A FWD has two terminals: an anode (A) and a cathode (K). The current through FWDs is in the
opposite direction to the IGBT current.
Note 2 to entry: FWDs are characterized by the capability to cope with high rates of decrease of current caused by
the switching behaviour of the IGBT.
3.2.4
IGBT-diode pair
arrangement of IGBT and FWD connected in inverse parallel
3.3 Operating states of converter
3.3.1
blocking state
condition of the converter, in which a turn-off signal is applied continuously to all IGBTs of the
converter
Note 1 to entry: Typically, the converter is in the blocking state condition after energization.
3.3.2
de-blocked state
condition of the converter, in which turn-on and turn-off signals are applied repetitively to IGBTs
of the converter
3.3.3
valve protective blocking
means of protecting the valve or converter from excessive electrical stress by the emergency
turn-off of all IGBTs in one or more valves
3.3.4
voltage step level
voltage step caused by switching of a valve or part of a valve during the de-blocked state of the
converter
Note 1 to entry: For valves of the controllable voltage source type, the voltage step level corresponds to the change
of voltage caused by switching one submodule or cell. For valves of the switch type, the voltage step level
corresponds to the change of voltage caused by switching the complete valve.
Note 2 to entry: Annex A gives an overview of VSC converters in HVDC power transmission.
3.4 VSC construction terms
3.4.1
VSC phase unit
equipment used to connect the two DC busbars to one AC terminal
3.4.2
switch type VSC valve
arrangement of IGBT-diode pairs connected in series and arranged to be switched
simultaneously as a single function unit
3.4.3
controllable voltage source type VSC valve
complete controllable voltage source assembly, which is generally connected between one AC
terminal and one DC terminal
3.4.4
diode valve
semiconductor valve containing only diodes as the main semiconductor devices, which might
be used in some VSC topologies
3.4.5
dynamic braking valve
complete controllable device assembly, which is used to control energy absorption in braking
resistor or other components
3.4.6
valve
VSC valve, dynamic braking valve or diode valve according to the context
3.4.7
submodule
part of a VSC valve comprising controllable switches and diodes connected to a half bridge or
full bridge arrangement, together with their immediate auxiliaries, storage capacitor, if any,
where each controllable switch consists of only one switched valve device connected in series

– 10 – IEC 62501:2024 CMV © IEC 2024
3.4.8
cell
MMC building block where each switch position consists of more than one IGBT-diode pair
connected in series
Note 1 to entry: See Figure A.13.
3.4.9
VSC valve level
smallest indivisible functional unit of VSC valve
Note 1 to entry: For any VSC valve in which IGBTs are connected in series and operated simultaneously, one VSC
valve level is one IGBT-diode pair including its auxiliaries (see Figure A.13). For MMC type without IGBT-diode pairs
connected in series one valve level is one submodule together with its auxiliaries (see Figure A.12).
3.4.10
diode valve level
part of a diode valve composed of a diode and associated circuits and components, if any
3.4.11
redundant levels
maximum number of series connected VSC valve levels or diode valve levels in a valve that
may be short-circuited externally or internally without affecting the safe operation of the valve
as demonstrated by type tests, and which if and when exceeded, would require shutdown of the
valve to replace the failed levels or acceptance of increased risk of failures
Note 1 to entry: In valve designs such as the cascaded two level converter, which contain two or more conduction
paths within each cell and have series-connected VSC valve levels in each path, redundant levels shall be counted
only in one conduction path in each cell.
3.4.12
dynamic braking valve level
part of a dynamic braking valve comprising a controllable switch and an associated diode, or
controllable switches and diodes connected in parallel, or controllable switches and diodes
connected to a half bridge arrangement, together with their immediate auxiliaries, storage
capacitor and energy dissipation resistors, if any
3.5 Valve structure terms
3.5.1
valve structure
structural components of a valve, required in order to physically support the valve modules
3.5.2
valve support
that part of the valve which mechanically supports and electrically insulates the active part of
the valve from earth
3.5.3
multiple valve unit
MVU
mechanical arrangement of 2 or more valves or 1 or more VSC phase units sharing a common
valve support
Note 1 to entry: A MVU might not exist in all topologies and physical arrangement of converters.

3.5.4
valve section
electrical assembly defined for test purposes, comprising a number of valve levels and other
components, which exhibits pro-rated electrical properties of a complete valve
Note 1 to entry: For valves of controllable voltage source type the valve section shall include cell or submodule DC
capacitor in addition to VSC valve levels.
Note 2 to entry: The minimum number of VSC or diode valve levels allowed in a valve section is defined along with
the requirements of each test.
4 General requirements
4.1 Guidelines for the performance of type tests
4.1.1 Evidence in lieu
Each design of valve shall be subjected to the type tests specified in this document. If the valve
is demonstrably similar to one previously tested, the supplier may, in lieu of performing a type
test or individual parts of it, submit a test report of a previous type test for consideration by the
purchaser. This should be accompanied by a separate report detailing the differences in the
design and demonstrating how the referenced type test satisfies the test objectives for the
proposed design. Conditions for use of evidence in lieu are listed in Table 1. 2
Table 1 – Conditions for use of evidence in lieu from another HVDC project
Type test Clause Conditions
Operational tests 6
• Equal or smaller number of valve levels to be tested
• Same valve level design
• Same valve electronics design
a
• Identical or lower voltage stress and thermal stress on
each valve level
Dielectric tests on valve support 7 • Identical valve structure, including cooling pipes, cable
structure
paths, earthing system, if any
• Same valve material and geometrical dimension
• Equal or higher air clearance to valve hall and other
related equipment inside the valve hall
• Equal or lower voltage stress, including DC voltage stress,
AC voltage stress and impulse voltage stresses
Dielectric tests on multiple 8
• Same MVU geometry between valves
valve unit
Dielectric tests between valve 9 • Identical valve structure, including cooling pipes, cable
terminals
paths and earthing system, if any
• Same valve material and geometrical dimension
• Equal or lower voltage stress
IGBT overcurrent turn-off test 10
• Same valve level design
• Same valve electronics design
• Identical or lower prospective current stress
Short-circuit current test 11 • Same valve level design
• Same short-circuit bypass components, if any, and
function
• Same valve electronics design
• Identical or lower short-circuit current stress
Tests for valve insensitivity to 12 • Same as those indicated for Clauses 6 and 9
electromagnetic disturbance
a
Semiconductor devices thermal stress is a combined effect of current and cooling. Device thermal stress is
characterised by the device junction temperature.

– 12 – IEC 62501:2024 CMV © IEC 2024
4.1.2 Selection of test object
This subclause does not apply to tests on the valve supporting structure and multiple valve unit.
The test object for those tests is defined in 7.2 and 8.3.
a) Type tests may be performed either on a complete valve or, in certain circumstances, on
valve sections MVU, or parts thereof, as indicated in Table 4.
b) The minimum number of valve levels to be operational type tested, depending on the valve
levels in a single valve, is as shown in Table 2. This number applies to the type tests in
Clauses 6, 10, 11 and 12. Those valve levels shall be tested in one test setup or multiple
setups on several valve sections as defined in those clauses.
Table 2 – Minimum number of valve levels to be operational type tested
as a function of the number of valve levels per valve
Number of valve levels, including Total number of valve levels to be
redundant level per valve tested
1 to 50 Number of valve levels in one valve
51 to 250 50
≥ 251 20 %
The minimum number of valve levels to be dielectric type tested can be equal to or lower
than the number specified for the operational type test.
The minimum number of valve levels, however, shall be representative of the valve dielectric
design. Details can be found in 9.2.
c) Generally, the same valve sections are recommended to be used for all type tests. However,
with the agreement of the purchaser and supplier, different tests may be performed on
different valve sections in parallel, in order to speed up the programme for executing the
tests. 3
d) Prior to commencement of type tests, the valve, valve sections and/or the components of
them should shall be demonstrated to have withstood the production tests to ensure proper
manufacture.
4.1.3 Test procedure
The tests shall be performed in accordance with IEC 60060, where applicable with due account
for IEC 60071 (all parts). Partial discharge measurements shall be performed in accordance
with IEC 60270.
4.1.4 Ambient temperature for testing
The tests shall be performed at the prevailing ambient temperature of the test facility, unless
otherwise specified.
4.1.5 Frequency for testing
AC dielectric tests can be performed at either 50 Hz or 60 Hz. For Operational tests, specific
requirements regarding the frequency for testing are given in the relevant clauses. Operational
tests shall be performed at the service frequency.
4.1.6 Test reports
At the completion of the type tests, the supplier shall provide type test reports in accordance
with Clause 15.
4.1.7 Conditions to be considered in determination of type test parameters
hall be determined based on the worst operating and fault
Type test parameters should s
conditions to which the valve can be subjected, according to system studies. Guidance on the
conditions can be found in CIGRE Technical Brochure No. 447.
4.2 Atmospheric correction factor
When specified in the relevant clause, atmospheric correction shall be applied to the test
voltages in accordance with IEC 60060-1. The reference conditions to which correction shall be
made are the following:
– pressure:
• If the insulation coordination of the tested part of the 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
s
will be installed is ≤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 procedure
s
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 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 ).
Realistic worst-case combinations of temperature and humidity which can occur in practice shall
be used for atmospheric correction.
The values to be used shall be specified by the supplier.
4.3 Treatment of redundancy
4.3.1 Operational tests
For operational tests, redundant valve levels shall not be short-circuited. The test voltages used
:
shall be adjusted by means of a scaling factor k
n
N
tut
k =
n
NN–
t r
where
N is the number of series valve levels in the test object;
tut
N is the total number of series valve levels in the valve;
t
N is the total number of redundant series valve levels in the valve.
r
4.3.2 Dielectric tests
For all dielectric tests between valve terminals, the redundant valve levels shall be short-
circuited. The location of valve levels to be short-circuited shall be agreed by the purchaser and
supplier.
– 14 – IEC 62501:2024 CMV © IEC 2024
NOTE Depending on the design, limitations may might be imposed upon the distribution of short-circuited valve
levels. For example, there may might be an upper limit to the number of short-circuited valve levels in one valve
section.
For all dielectric tests on valve section, the test voltages used shall be adjusted by means of a
scaling factor k :
N
tu
k =
NN–
t r
where
N is the number of series valve levels not short circuit connected in the test object;
tu
N is the total number of series valve levels in the valve;
t
N is the total number of redundant series valve levels in the valve.
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4.4 Criteria for successful type testing
4.4.1 General
Experience in semiconductor application shows that, even with the most careful design of
valves, it is not possible to avoid occasional random failures of valve 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 quantitati
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