IEC 62924:2017

IEC 62924 ®
Edition 1.0 2017-01
INTERNATIONAL
STANDARD
NORME
INTERNATIONALE
Railway applications – Fixed installations – Stationary energy storage system for
DC traction systems
Applications ferroviaires – Installations fixes – Système stationnaire de stockage
d’énergie pour les systèmes de traction en courant continu

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IEC 62924 ®
Edition 1.0 2017-01
INTERNATIONAL
STANDARD
NORME
INTERNATIONALE
Railway applications – Fixed installations – Stationary energy storage system for

DC traction systems
Applications ferroviaires – Installations fixes – Système stationnaire de stockage

d’énergie pour les systèmes de traction en courant continu

INTERNATIONAL
ELECTROTECHNICAL
COMMISSION
COMMISSION
ELECTROTECHNIQUE
INTERNATIONALE
ICS 45.060.01 ISBN 978-2-8322-3860-8

– 2 – IEC 62924:2017 © IEC 2017
CONTENTS
FOREWORD . 5
INTRODUCTION . 7
1 Scope . 8
2 Normative references . 8
3 Terms, definitions and abbreviations . 9
3.1 Terms and definitions . 9
3.2 Abbreviations . 13
4 Configuration of stationary energy storage systems . 13
4.1 General . 13
4.2 Example system configuration using an electronic power converter . 14
4.3 Example system configuration without an electronic power converter . 14
4.4 Accessory and auxiliary components. 15
5 Service conditions . 15
5.1 Environmental conditions . 15
5.2 Electrical service conditions . 15
6 Investigation before the installation of stationary ESS . 15
6.1 General . 15
6.2 Decision on the installation location and capacity of the stationary ESS . 16
6.3 Evaluation of the positive effects of introducing a stationary ESS . 16
6.4 Coordination with other systems . 16
7 Performance requirements. 16
7.1 General requirements . 16
7.1.1 Rating . 16
7.1.2 System capability to conform with the specified duty cycle . 18
7.1.3 Short-time withstand current capability . 18
7.1.4 Calculation of charge-discharge efficiency . 18
7.1.5 Temperature rise . 19
7.1.6 Lifetime requirements . 19
7.2 Control and protection functions . 19
7.2.1 Charge/discharge control functions . 19
7.2.2 Short circuit protection function . 20
7.2.3 Earth-fault protection function . 20
7.2.4 Overload protection function . 20
7.2.5 Disconnection functions . 20
7.3 Electromagnetic compatibility (EMC) . 20
7.4 Failure conditions for the stationary ESS . 20
7.5 Mechanical characteristics . 21
7.5.1 General . 21
7.5.2 Earthing . 21
7.5.3 Degree of protection . 21
7.6 Rating plate . 22
7.7 Terminals of the main circuit . 22
8 Tests . 22
8.1 Types of test . 22
8.1.1 General . 22
8.1.2 Type test . 23

8.1.3 Routine test . 23
8.1.4 Commissioning test . 23
8.1.5 Test categories . 23
8.2 Tests . 24
8.2.1 Visual inspection . 24
8.2.2 Degree of protection test . 24
8.2.3 Test of accessory and auxiliary components . 24
8.2.4 Insulation test . 24
8.2.5 Start and stop sequence test . 25
8.2.6 Checking of the protective devices . 25
8.2.7 Charge/discharge control functions test . 25
8.2.8 Light load functional test . 25
8.2.9 Temperature rise test . 25
8.2.10 Measurement of charge-discharge efficiency . 26
8.2.11 Noise measurement . 26
8.2.12 EMC test . 26
8.2.13 Harmonic measurement . 27
Annex A (normative) Methods of simulation and measurement on site . 28
A.1 General . 28
A.2 System design to use simulation software . 28
A.2.1 General . 28
A.2.2 Simulation software . 28
A.2.3 Input parameters for simulation . 28
A.2.4 Evaluation of simulation results . 30
A.3 Validation of the effect of installing an actual ESS . 30
A.3.1 General . 30
A.3.2 Before installation . 30
A.3.3 After installation. 31
Annex B (informative) State of charge (SOC) and state of energy (SOE) for batteries
and capacitors . 32
B.1 Content of capacity and energy . 32
B.1.1 General . 32
B.1.2 Theoretical energy . 33
B.1.3 Rated energy . 33
B.1.4 Usable energy . 33
B.1.5 Theoretical, rated and usable capacity . 34
B.2 Content of SOC and SOE . 34
B.2.1 General . 34
B.2.2 Theoretical purpose . 35
B.2.3 Common purpose . 35
B.2.4 Effective or practical purpose . 35
B.2.5 Coefficient of usage . 36
Annex C (informative) Duty cycle examples . 37
Bibliography . 40

Figure 1 – Common system configuration of stationary ESS . 13
Figure 2 – Example system configuration using an electronic power converter . 14
Figure 3 – Example system configuration without an electronic power converter . 15

– 4 – IEC 62924:2017 © IEC 2017
Figure B.1 – Difference of capacity and energy content . 32
Figure C.1 – Duty cycle for class I to class III . 38
Figure C.2 – Duty cycle for class IV to class VI . 38
Figure C.3 – Duty cycle for class VII and class VIII . 38
Figure C.4 – Duty cycle for class IX . 39

Table 1 – Immunity level . 21
Table 2 – List of tests . 24
Table A.1 – Operational data . 29
Table A.2 – Rolling stock data . 29
Table A.3 – DC power supply network data . 30
Table A.4 – Measurement data . 31
Table C.1 – Duty cycle . 37

INTERNATIONAL ELECTROTECHNICAL COMMISSION
____________
RAILWAY APPLICATIONS – FIXED INSTALLATIONS – STATIONARY
ENERGY STORAGE SYSTEM FOR DC TRACTION SYSTEMS

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
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agreement between the two organizations.
2) The formal decisions or agreements of IEC on technical matters express, as nearly as possible, an international
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3) IEC Publications have the form of recommendations for international use and are accepted by IEC National
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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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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 62924 has been prepared by IEC technical committee 9: Electrical
equipment and systems for railways.
The text of this standard is based on the following documents:
FDIS Report on voting
9/2221/FDIS 9/2244/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.
This document has been drafted in accordance with the ISO/IEC Directives, Part 2.

– 6 – IEC 62924:2017 © IEC 2017
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.
INTRODUCTION
To save natural resources and counteract global warming, techniques to save energy and/or
to improve environmental characteristics are drawing strong interest. In the railway industry,
electric rail vehicles fitted with regenerative braking systems have been introduced, not only
to save energy, but also to ease maintenance and to reduce the adverse effects of heat
generated during braking (especially in tunnels).
However, in DC electric railways, when a train regenerates power, usually the power has to
be consumed within the DC network, because DC power supply substations are usually not
reversible. There is no guarantee that adequate load exists for regenerative braking trains; in
such a circumstance, regenerative braking becomes ineffective, either in part or in whole. In
this situation, the power supply network is unreceptive. Among the emerging technologies to
improve receptivity is stationary energy storage systems (ESSs). A stationary ESS charges
regenerative energy when the power supply network is unreceptive and stores it for use at a
later time.
International Standards for stationary ESSs have not been issued. Before ESSs become
widely used, international standardization of the basic system structure and measurement
method for efficiency, etc., will serve as a guideline for users and manufacturers who want to
introduce ESSs.
– 8 – IEC 62924:2017 © IEC 2017
RAILWAY APPLICATIONS – FIXED INSTALLATIONS – STATIONARY
ENERGY STORAGE SYSTEM FOR DC TRACTION SYSTEMS

1 Scope
This document specifies the requirements and test methods for a stationary energy storage
system to be introduced as a trackside installation and used in a power supply network of a
DC electrified railway. This system can take electrical energy from the DC power supply
network, store the energy, and supply the energy back to the DC power supply network when
necessary. This document does not apply to onboard energy storage systems.
This document applies to systems which are installed to achieve one or more of the following
objectives.
• Absorption of regenerative energy:
– effective use of regenerative energy (saving energy);
– reduction of rolling stock maintenance (reduction of brake shoe/pad wear, etc.);
– avoidance of adverse effects of heat generated during braking (e.g. in tunnels, etc.).
• Power compensation:
– compensation of line voltage;
– reduction of peak power;
– reduction in the requirement of the rectifier ratings.
If this system is combined with one or more of the following functions, this document may be
used as a guideline:
• reverse transmission of regenerated power to the upstream power supply network
(e.g. inverting or reversible substations);
• use of the regenerated energy for purposes other than the running of trains, such as for
station facilities, etc.;
• resistive consumption of regenerated power.
Although it is assumed that the system uses the following typical energy storage technologies,
this document also applies to other existing or future technologies:
• batteries (lithium-ion, nickel metal hydride, etc.);
• capacitors (electric double layer capacitors, lithium-ion capacitors, etc.);
• flywheels.
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 60146 (all parts), Semiconductor converters
IEC 60529, Degrees of protection provided by enclosures (IP Code)
IEC 60850, Railway applications – Supply voltages of traction systems

IEC 61936-1, Power installations exceeding 1 kV a.c. – Part 1: Common rules
IEC 61992-7-1:2006, Railway applications – Fixed installations – DC switchgear – Part 7-1:
Measurement, control and protection devices for specific use in d.c. traction systems –
Application guide
IEC 62236 (all parts), Railway applications – Electromagnetic compatibility
IEC 62236-1, Railway applications – Electromagnetic compatibility – Part 1: General
IEC 62236-5, Railway applications – Electromagnetic compatibility – Part 5: Emission and
immunity of fixed power supply installations and apparatus
IEC 62590:2010, Railway applications – Electronic power converters for substations
3 Terms, definitions and abbreviations
3.1 Terms and definitions
For the purposes of this document, the terms and definitions given in IEC 60146 (all parts)
and the following 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
3.1.1
energy storage system
ESS
system that can take electrical energy from the DC power supply network, store the energy,
and supply the energy back to the DC power supply network when necessary
Note 1 to entry: This note applies to the French language only.
3.1.2
regenerative braking
electro-dynamic braking in which the energy produced by the motors is fed into the contact
line or into energy storage on-board devices
Note 1 to entry: Examples of storage devices: batteries, flywheels, etc.
[SOURCE: IEC 60050-811:—, 811-06-25]
3.1.3
regenerative energy
electric energy that is supplied from railway vehicles to the contact lines when power is
generated by regenerative braking
3.1.4
energy storage unit
ESU
device to which electrical energy is charged and from which electrical energy is discharged
Note 1 to entry: This note applies to the French language only.

– 10 – IEC 62924:2017 © IEC 2017
3.1.5
electronic power converter
operative unit for electronic power conversion, comprising one or more electronic valve
devices, transformers and filters if necessary and auxiliaries if any
[SOURCE: IEC 60050-551:1998, 551-12-01]
3.1.6
charge-discharge characteristics
characteristics given to the controller of the ESS so that the energy management of the ESS
is properly performed under the required duty cycle
3.1.7
duty cycle
time pattern of power supplied to or returned from the electronic power converter or the ESU
3.1.8
short-time withstand current capability
capability to deliver current for a specified short period of time under specified usage and
operating conditions
3.1.9
charge-discharge efficiency
ratio of discharge energy to charge energy of an ESS through its electrical terminals
Note 1 to entry: The efficiency is calculated using the equation described in 7.1.4.
3.1.10
type test
conformity test made on one or more items representative of the production
[SOURCE: IEC 60050-151:2001, 151-16-16]
3.1.11
routine test
conformity test made on each individual item during or after manufacture
[SOURCE: IEC 60050-151:2001, 151-16-17]
3.1.12
commissioning test
test on an item carried out on site, to prove that it is correctly installed and can operate
correctly
[SOURCE: IEC 60050-151:2001, 151-16-24]
3.1.13
system charge current
current flowing from the power supply network to the ESS
3.1.14
system discharge current
current flowing from the ESS to the power supply network
3.1.15
system charge power
power flowing from the power supply network to the ESS

3.1.16
system discharge power
power flowing from the ESS to the power supply network
3.1.17
end of life
EOL
point at which the ESU cannot fulfil the required functionality or duty cycle as initially agreed
between the user and the manufacturer
Note 1 to entry: This note applies to the French language only.
3.1.18
capacity
electrical charge that can be delivered from the ESU
Note 1 to entry: In case of a battery, the electrical charge is often expressed in ampere-hours (Ah).
Note 2 to entry: In case of a capacitor, the electrical charge is often expressed in coulomb (C).
Note 3 to entry: Capacitance is measured in farad (F), which is charge (C) divided by voltage (V), and is different
from capacity.
3.1.19
theoretical capacity
maximum capacity available without loss
[SOURCE: IEC 62864-1:2016, 3.1.17.2]
3.1.20
rated capacity
available capacity measured according to the “rating” conditions as expressed in the relevant
standard
Note 1 to entry: Refer to IEC 62928.
[SOURCE: IEC 62864-1:2016, 3.1.17.3]
3.1.21
usable capacity
capacity available to be discharged depending upon applications
[SOURCE: IEC 62864-1:2016, 3.1.17.4]
3.1.22
theoretical energy
maximum energy available without loss stored in the ESU
[SOURCE: IEC 62864-1:2016, 3.1.18.1]
3.1.23
rated energy
energy available measured according to the “rating” conditions as expressed in the relevant
standard
Note 1 to entry: Practical definitions of rated energy are dependent upon chosen technologies.
[SOURCE: IEC 62864-1:2016, 3.1.18.2]

– 12 – IEC 62924:2017 © IEC 2017
3.1.24
usable energy
energy available to be discharged depending upon applications
[SOURCE: IEC 62864-1:2016, 3.1.18.3]
3.1.25
state of charge
SOC
remaining capacity to be discharged, normally expressed as a percentage of full capacity as
expressed in relevant standards
Note 1 to entry: Practical definitions of SOC are dependent upon chosen technologies. SOC is applicable to
batteries.
Note 2 to entry: For detailed description, see Annex B.
Note 3 to entry: This note applies to the French language only.
[SOURCE: IEC 62864-1:2016, 3.1.13, modified – Note 1 to entry was modified and Notes 2
and 3 to entry were added.]
3.1.26
state of energy
SOE
remaining energy to be discharged, normally expressed as a percentage of full energy as
expressed in relevant standards
Note 1 to entry: Practical definitions of SOE are dependent upon chosen technologies. SOE is applicable to all
storage technologies.
Note 2 to entry: For detailed description, see Annex B.
Note 3 to entry: This note applies to the French language only.
[SOURCE: IEC 62864-1:2016, 3.1.14, modified – Note 1 to entry was modified and Notes 2
and 3 to entry were added.]
3.1.27
charge energy
energy supplied to the ESS through its electrical terminals
3.1.28
discharge energy
energy returned from the ESS through its electrical terminals
3.1.29
rate of energy exchange
maximum energy that can be charged into or discharged from the ESS during a
defined time period under rating conditions
3.1.30
self-discharge
reduction of charge or energy of an ESU that occurs in a period of time during which no
energy is either charged into or discharged from the ESU
3.1.31
stand-by losses
losses of an ESS that occur when no power is either charged into or discharged from the ESS
under its operation
3.1.32
per unit
p.u.
methodology used to simplify equations and the presentation of electrical parameters by
expressing them as a fraction of a reference parameter:
 actual
p.u.value=
 
base
 
where the actual and base values are of the same quantity, e.g. voltage, current, impedance,
etc.
[SOURCE: IEC TR 61000-2-14:2006, 3.13]
3.2 Abbreviations
ATO automatic train operation
ATP automatic train protection
BOL beginning of life
DCCB DC circuit breaker
EDLC electric double-layer capacitor
EOL end of life
ESU energy storage unit
ESS energy storage system
IP international protection (against ingress) / ingress protection
SOC state of charge
SOE state of energy
4 Configuration of stationary energy storage systems
4.1 General
The stationary energy storage systems to which this document is applicable shall have the
common system configuration shown in Figure 1.
+
DC bus ACTB ESU
– ESS
ACTB: Apparatus for Connecting the ESU To the DC Bus

IEC
Figure 1 – Common system configuration of stationary ESS
In Figure 1, ESU may be of any available storage technology, such as batteries (lithium-ion,
nickel metal hydride, etc.), capacitors (electric double layer capacitors, lithium-ion capacitors,
etc.) or flywheels. Also, in Figure 1, there may be a wide variety of the detailed configuration
marked as ACTB (apparatus for connecting the ESU to the DC bus).

– 14 – IEC 62924:2017 © IEC 2017
The configuration of ESS shall be categorized into the following two categories:
a) system using an electronic power converter in the ACTB; and
b) directly connected system without an electronic power converter in the ACTB.
To give an overview of how an ESS can be implemented, two example configurations are
explained in more detail in 4.2 and 4.3, representing categories a) and b), respectively. These
examples are not meant to give constraints on the final architecture of the ESS.
4.2 Example system configuration using an electronic power converter
Figure 2 shows an example system configuration in which a power converter and an ESU are
combined.
In this configuration, the system charge and/or discharge currents can be controlled by the
DC/DC converter. Also, many actual examples can be found in which no reactor L is used in
the position shown in Figure 2.
+
DCCB (L)
DC bus
ESU
(Li-ion battery)
CH
–
DCCB: DC circuit breaker
CH: Chopper
L: DC reactor
ESU: Energy storage unit
IEC
Figure 2 – Example system configuration using an electronic power converter
4.3 Example system configuration without an electronic power converter
Figure 3 shows an example system configuration in which an ESU is used without any
electronic power converter.
In this configuration, the ESS has no ability to control the system charge and/or discharge
currents; they are determined by the voltage of the power supply network and the voltage and
internal resistance of the ESU. Also, the DCCBs are used on both the positive-side and the
negative-side connections for improved safety.

+
(L)
DC bus
ESU
DCCB
(Nickel metal hydride battery)
–
DCCB: DC circuit breaker
L: DC reactor
ESU: Energy storage unit
IEC
Figure 3 – Example system configuration without an electronic power converter
4.4 Accessory and auxiliary components
There may be many different configurations for accessory and auxiliary components and their
power supplies. Examples of such components which it is indispensable to integrate into the
stationary ESS include, but are not limited to:
• control and protection devices;
• cooling systems, including, for example, cooling fans or heat pumps; and
• heating systems.
The power of these components may be supplied by connecting the auxiliary power supply
unit to the same DC bus as the main circuit of the stationary ESS itself, or by any kind of
external power sources separated from the main circuit.
5 Service conditions
5.1 Environmental conditions
The environmental conditions specified in 5.2 of IEC 62590:2010 shall be applied.
5.2 Electrical service conditions
The electrical service conditions specified in 5.3 of IEC 62590:2010 shall be applied.
6 Investigation before the installation of stationary ESS
6.1 General
The major aspects of system design for a stationary ESS are as follows:
a) decision on the installation location and capacity of the ESS;
b) evaluation of the positive effects of introducing an ESS;
c) coordination with other systems;
d) other investigations.
The design of the ESS and the power supply network into which the ESS is introduced shall
be performed using an appropriate evaluation method. A simulation tool whose validity has

– 16 – IEC 62924:2017 © IEC 2017
been either proved through preceding projects or agreed upon between the user and the
manufacturer should be used to perform the evaluation.
6.2 Decision on the installation location and capacity of the stationary ESS
In determining the optimum installation location and capacity of the stationary ESS, the
charge and discharge characteristics of the ESU as well as the duty cycle, the rated capacity
and the usable capacity defined in 7.1.1.7, 7.1.1.8 and 7.1.1.9, respectively, shall be fully
considered.
The methods of simulation and/or measurement at the site are given in Annex A.
These decisions may also be made based on the actual measurement data obtained by
temporarily installing an ESS at the site.
6.3 Evaluation of the positive effects of introducing a stationary ESS
If any simulation tool is used to evaluate the positive effects of the introduction, the simulation
results obtained in the simulation described in 6.2 shall be used.
The methods of simulation and/or measurement at the site are given in Annex A.
These evaluations may be performed based on the actual measurement data obtained by
temporarily installing an ESS at the site.
6.4 Coordination with other systems
Upon evaluating the harmonic content in the system charge/discharge current and its effects
on other systems, especially the signalling and/or communication systems, an effective
simulation tool shall be used to simulate and verify the effects before the delivery of the ESS
unless otherwise agreed between the user and the manufacturer.
These evaluations may also be performed using the actual measurement data obtained by
operating an ESS.
The manufacturer shall request the user to specify the frequency band that might adversely
affect their signalling and/or communication systems.
7 Performance requirements
7.1 General requirements
7.1.1 Rating
7.1.1.1 General
The rated values of the ESS are the values determined in the system design such that the
system can deliver the output without exceeding any specified limit values, including those of
the parts used, or without causing any damage, when the system is operated under the
specified operating conditions.
Unless otherwise specified, any rated value shall be indicated on the rating plate according to
7.6.
The parameters described in 7.1.1.2 to 7.1.1.10 shall also apply to systems without electronic
power converters. To achieve them, control functions realized by electronic power converters
are not always necessary.
7.1.1.2 Rated system voltage
The rated system voltage shall be U as specified in IEC 60850. If any other value is to be
max1
selected as the rated system voltage in order to select an optimum capacity, the details shall
be discussed and agreed between the user and the manufacturer.
7.1.1.3 Rated system charge current
The rated system charge current is defined as the maximum system charge current under
normal operating conditions.
7.1.1.4 Rated system discharge current
The rated system discharge current is defined as the maximum system discharge current
under normal operating conditions.
7.1.1.5 Rated system charge power
The rated system charge power is defined as the product of the rated system voltage defined
in 7.1.1.2 and the rated system charge current defined in 7.1.1.3.
7.1.1.6 Rated system discharge power
The rated system discharge power is defined as the product of the rated system voltage
defined in 7.1.1.2 and the rated system discharge current defined in 7.1.1.4.
7.1.1.7 Duty cycle
The system shall be specified with the required duty cycle of operation, based upon which the
charging and discharging operations shall be performed. This duty cycle shall be agreed
between the user and the manufacturer. Examples of such duty cycles are shown in Annex C.
7.1.1.8 Rated capacity/energy
The rated capacity or the rated energy are as defined in 3.1.20 or in 3.1.23. They are the
available capacity or energy measured according to the “rating” conditions as expressed in
relevant standards.
The rated capacity or the rated energy shall be specified together with the rated system
charge/discharge power.
7.1.1.9 Usable charge/discharge capacity/energy
The usable charge/discharge capacity or the usable charge/discharge energy are as defined
in 3.1.21 or in 3.1.24. They are the usable portion of available capacity/energy within a pre-
defined range of SOC or voltage limits. The maximum and minimum limits are parameters
typically defined by the user or the manufacturer.
The usable capacity or the usable energy shall be specified together with the rated system
charge/discharge power.
7.1.1.10 Rate of energy exchange
The rate of energy exchange, norma
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