IEC 60931-1:2025

IEC 60931-1 ®
Edition 3.0 2025-06
INTERNATIONAL
STANDARD
NORME
INTERNATIONALE
Shunt power capacitors of the non-self-healing type for AC systems having a
rated voltage up to and including 1 000 V –
Part 1: General
Condensateurs shunt de puissance non autorégénérateurs pour réseaux à
courant alternatif de tension assignée inférieure ou égale à 1 000 V –
Partie 1 : Généralités
ICS 29.120.99, 31.060.70 ISBN 978-2-8327-0506-3

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CONTENTS
FOREWORD. 4
1 Scope . 6
2 Normative references . 6
3 Terms and definitions . 7
4 Service conditions . 10
4.1 Normal service conditions . 10
4.2 Unusual service conditions . 11
5 Test requirements . 11
5.1 General . 11
5.2 Test conditions . 11
6 Tests . 11
6.1 Classification . 11
6.1.1 General . 11
6.1.2 Routine tests . 11
6.1.3 Type tests . 12
6.1.4 Acceptance tests. 12
6.2 Capacitance measurement and output calculation . 13
6.2.1 Measuring procedure . 13
6.2.2 Capacitance tolerances . 13
6.3 Measurement of the tangent of the loss angle (tan δ) of the capacitor . 13
6.3.1 Measuring procedure . 13
6.3.2 Loss requirements . 14
6.4 Voltage tests between terminals . 14
6.4.1 Routine test . 14
6.4.2 Type test . 14
6.5 Voltage tests between terminals and container . 14
6.5.1 Routine test . 14
6.5.2 Type test . 15
6.6 Test of internal discharge device . 15
6.7 Sealing test . 15
6.8 Thermal stability test . 16
6.9 Measurement of the tangent of the loss angle (tan δ) of the capacitor at
elevated temperature . 17
6.9.1 Measuring procedure . 17
6.9.2 Requirements . 17
6.10 Lightning impulse voltage test between terminals and container . 17
6.11 Discharge test . 18
6.12 Ageing test . 18
6.13 Destruction test . 18
6.14 Disconnecting test on internal fuses . 18
6.14.1 General . 18
6.14.2 Test procedure . 19
6.14.3 Capacitance measurement . 19
6.14.4 Inspection of the unit . 20
6.14.5 Voltage test after opening the container . 20
7 Maximum permissible voltage . 20
7.1 Long-duration voltages . 20
7.2 Switching voltages . 21
8 Maximum permissible current . 21
9 Discharge device . 21
10 Container connections . 22
11 Protection of the environment . 22
12 Other safety requirements . 22
13 Marking of the unit . 22
13.1 Rating plate . 22
13.2 Standardized connection symbols . 23
13.3 Warning plate . 23
14 Marking of the bank . 23
14.1 Instruction sheet or rating plate . 23
14.2 Warning plate . 23
15 General . 24
16 Choice of the rated voltage . 24
17 Operating temperature . 25
17.1 General . 25
17.2 Installation . 25
17.3 High ambient air temperature . 25
17.4 Evaluation of losses . 25
18 Special service conditions . 26
19 Overvoltages . 26
20 Overload currents . 27
21 Switching and protective devices and connections . 27
22 Choice of creepage distance . 28
23 Capacitors connected to systems with audio-frequency remote control. 28
24 Electromagnetic compatibility (EMC) . 29
24.1 Emission . 29
24.2 Immunity . 29
24.2.1 General . 29
24.2.2 Low-frequency disturbances . 29
24.2.3 Conducted transients and high-frequency disturbances . 29
24.2.4 Electrostatic discharges . 29
24.2.5 Magnetic disturbances . 29
24.2.6 Electromagnetic disturbances . 30
Annex A (normative) Additional definitions, requirements and tests for power filter
capacitors . 31
A.1 Additional terms and definitions . 31
A.1.1 Band-pass and high-pass filter capacitor (filter capacitor) . 31
A.1.2 Rated voltage (U ) (see 3.11) . 31
N
A.1.3 Rated output (Q ) (see 3.10) . 31
N
A.1.4 Rated current (I ) (see 3.16) . 31
N
A.2 Quality requirements and tests . 31
A.2.1 Capacitance tolerance . 31
A.2.2 Voltage test between terminals (see 6.4) . 32
A.2.3 Thermal stability test (see 6.8) . 32
A.3 Overloads – Maximum permissible current (see Clause 8) . 32
A.4 Markings – Instruction sheet or rating plate (see 14.1) . 32
A.5 Guide for installation and operation – Choice of the rated voltage
(see Clause 16). 32
Annex B (informative) Formulae for capacitors and installations . 33
B.1 Computation of the output of three-phase capacitor from three single-phase
capacitance measurements . 33
B.2 Resonance frequency . 33
B.3 Voltage rise . 33
B.4 Inrush transient current . 34
B.4.1 Switching in of single capacitor . 34
B.4.2 Switching of capacitors in parallel with energized capacitor(s) . 34
B.4.3 Discharge resistance in single-phase units or in one-phase or
polyphase units . 34
Annex C (normative) Test procedures for the disconnecting test on internal fuses . 36
C.1 General . 36
C.2 Test procedure . 36
Annex D (informative) Guidance for coordination of fuse protection . 38
D.1 General . 38
D.2 Protection sequence . 38
Bibliography . 39

Figure B.1 – k values depending on the method of connection of the resistors with the
capacitor units . 35

Table 1 – Letter symbols for upper limit of temperature range . 10
Table 2 – Ambient air temperature for the thermal stability test . 16
Table 3 – Admissible voltage levels in service . 20

INTERNATIONAL ELECTROTECHNICAL COMMISSION
____________
Shunt power capacitors of the non-self-healing type for AC systems
having a rated voltage up to and including 1 000 V –
Part 1: General
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
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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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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
members of its technical committees and IEC National Committees for any personal injury, property damage or
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) IEC draws attention to the possibility that the implementation of this document may involve the use of (a)
patent(s). IEC takes no position concerning the evidence, validity or applicability of any claimed patent rights in
respect thereof. As of the date of publication of this document, IEC had not received notice of (a) patent(s), which
may be required to implement this document. However, implementers are cautioned that this may not represent
the latest information, which may be obtained from the patent database available at https://patents.iec.ch. IEC
shall not be held responsible for identifying any or all such patent rights.
IEC 60931-1 has been prepared by IEC technical committee 33: Power capacitors and their
applications. It is an International Standard.
This third edition cancels and replaces second edition published in 1996 and
Amendment 1:2002. This edition constitutes a technical revision.
This edition includes the following significant technical changes with respect to the previous
edition:
a) integration of IEC 60931-3 within IEC 60931-1;
b) deletion of self-healing test.
The text of this International Standard is based on the following documents:
Draft Report on voting
33/721/FDIS 33/725/RVD
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.
A list of all parts in the IEC 60931 series, published under the general title Shunt power
capacitors of the non-self-healing type for AC systems having a rated voltage up to and
including 1 000 volts, can be found on the IEC website.
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.
1 Scope
This part of IEC 60931 is applicable to both non-self-healing capacitor units and non-self-
healing capacitor banks intended to be used, particularly, for power-factor correction of AC
power systems having a rated voltage up to and including 1 000 V and frequencies 15 Hz to
60 Hz.
This document also applies to capacitors intended for use in power filter circuits. Additional
definitions, requirements, and tests for filter capacitors are given in Annex A.
The following capacitors are excluded from this part of IEC 60931:
– Shunt power capacitors of the self-healing type for AC systems having a rated voltage up
to and including 1 000 V (IEC 60831 series [1] )
– Shunt capacitors for AC power systems having a rated voltage above 1 000 V (IEC 60871
series [2])
– Power capacitors for induction heating installations (IEC 60110 series [3])
– Series capacitors for power systems (IEC 60143 series [4])
– Capacitors for motor applications (IEC 60252 series [5])
– Coupling capacitors and capacitor dividers (IEC 60358 series [6])
– Capacitors for power electronics (IEC 61071 [7])
– Small AC capacitors to be used for fluorescent and discharge lamps (IEC 61048 [8] and
IEC 61049 [9])
– Capacitors for suppression of radio interference (under consideration)
– Capacitors intended to be used in various types of electrical equipment and thus considered
as components
– Capacitors intended for use with DC voltage superimposed on the AC voltage
– Shunt power capacitors of the self-healing type for AC systems having a rated voltage above
1 000 V (IEC 63210 [10])
Accessories such as insulators, switches, instrument transformers, fuses, etc., are to be in
accordance with the relevant IEC standards.
The purpose of this document is:
a) to formulate uniform rules regarding performances, testing and rating;
b) to formulate specific safety rules;
c) to provide a guide for installation and operation.
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 60060-1, High-voltage test techniques – Part 1: General definitions and test requirements
IEC 60931-2, Shunt power capacitors of the non-self-healing type for a.c. systems having a
rated voltage up to and including 1000 V – Part 2: Ageing test and destruction test
___________
Numbers in square brackets refer to the Bibliography.
IEC 61000-2-2:2002, Electromagnetic compatibility (EMC) – Part 2-2: Environment –
Compatibility levels for low-frequency conducted disturbances and signalling in public low-
voltage power supply systems
IEC TR 61000-4-1, Electromagnetic compatibility (EMC) – Part 4-1: Testing and measurement
techniques – Overview of IEC 61000-4 series
3 Terms and definitions
For the purposes of this document, the following terms and definitions apply.
ISO and IEC maintain terminology databases for use in standardization at the following
addresses:
• IEC Electropedia: available at https://www.electropedia.org/
• ISO Online browsing platform: available at https://www.iso.org/obp
3.1
capacitor element
element
device consisting essentially of two electrodes separated by a dielectric
[SOURCE: IEC 60050-436:1990 [11], 436-01-03]
3.2
capacitor unit
unit
assembly of one or more capacitor elements in the same container with terminals brought out
[SOURCE: IEC 60050-436:1990 [11], 436-01-04]
3.3
non-self-healing capacitor
capacitor in which the dielectric, after local break-down, is not restored
3.4
capacitor bank
bank
number of capacitor units connected so as to act together
[SOURCE: IEC 60050-436:1990 [11], 436-01-06]
3.5
capacitor
generic term, encompassing the notions of capacitor unit and capacitor bank
Note 1 to entry: In this part of IEC 60931, the word capacitor is used when it is not necessary to lay particular stress
upon the different meanings of the words capacitor unit or capacitor bank.
[SOURCE: IEC 60831-1:2014 [12], 3.5]
3.6
discharge device
device which may be incorporated in a capacitor, capable of reducing the
voltage between the terminals practically to zero, within a given time, after the capacitor has
been disconnected from a network
[SOURCE: IEC 60050-436:1990 [11], 436-03-15, modified – "intended to" replaced with
"capable of", "to a given value" replaced with "practically to zero"]
3.7
internal fuse
fuse connected inside a capacitor unit, in series with an element or a group of
elements
[SOURCE: IEC 60050-436:1990 [11], 436-03-16]
3.8
line terminal
terminal intended for connection to a line conductor of a network
Note 1 to entry: In polyphase capacitors, a terminal intended to be connected to the neutral conductor is not
considered to be a line terminal.
[SOURCE: IEC 60050-436:1990 [11], 436-03-01]
3.9
rated capacitance
C
N
capacitance value for which the capacitor has been designed
[SOURCE: IEC 60050-436:1990 [11], 436-01-12, modified – "derived from the values of rated
output, voltage and frequency of the capacitor" replaced with "for which the capacitor has been
designed"]
3.10
rated output
Q
N
reactive power derived from the rated values of capacitance, frequency and
voltage
[SOURCE: IEC 60050-436:1990 [11], 436-01-16, modified – "for which the capacitor has been
designed" replaced with "derived from the rated values of capacitance, frequency and voltage"]
3.11
rated voltage
U
N
RMS value of the alternating voltage for which the capacitor has been designed
Note 1 to entry: In the case of capacitors consisting of one or more separate circuits (such as single-phase units
intended for use in polyphase connection, or polyphase units with separate circuits), U refers to the rated voltage
N
of each circuit.
Note 2 to entry: For polyphase capacitors with internal electrical connections between the phases, and for
polyphase capacitor banks, U refers to the phase-to-phase voltage.
N
[SOURCE: IEC 60050-436:1990 [11], 436-01-15]
3.12
rated frequency
f
N
frequency for which the capacitor has been designed
[SOURCE: IEC 60050-436:1990 [11], 436-01-14]
3.13
rated current
I
N
RMS value of the alternating current for which the capacitor has been designed
[SOURCE: IEC 60050-436:1990 [11], 436-01-13]
3.14
capacitor losses
active power dissipated in the capacitor
Note 1 to entry: All loss-producing components should be included, for example:
– for a unit, losses from dielectric, internal fuses, internal discharge resistor, connections, etc.
– for a bank, losses from units, external fuses, busbars, discharge and damping reactors, etc.
[SOURCE: IEC 60050-436:1990 [11], 436-04-10]
3.15
tangent of the loss angle
tan δ
ratio between the equivalent series resistance and the capacitive reactance of
the capacitor at specified sinusoidal alternating voltage and frequency
[SOURCE: IEC 60050-436:1990 [11], 436-04-11]
3.16
ambient air temperature
temperature of the air at the proposed location of the capacitor.
3.17
cooling air temperature
temperature of the cooling air measured at the hottest position in the bank, under steady-state
conditions, midway between two units
Note 1 to entry: If only one unit is involved, it is the temperature measured at a point approximately 0,1 m away
from the capacitor container and at two-thirds of the height from its base.
[SOURCE: IEC 60831-1:2014 [12], 3.22]
3.18
steady-state condition
thermal equilibrium attained by the capacitor at constant output and at constant ambient air
temperature
3.19
residual voltage
the voltage remaining on the terminals of a capacitor at a certain time following disconnection
3.20
rated voltage
U
Ne
RMS value of the alternating voltage for which the capacitor element
has been designed
4 Service conditions
4.1 Normal service conditions
This document gives requirements for capacitors intended for use in the following conditions:
a) Residual voltage at energization
Not to exceed 10 % rated voltage (Clause 9, Clause 19, and Annex B).
b) Altitude
Not exceeding 2 000 m.
c) Ambient air temperature categories
Capacitors are classified in temperature categories, each category being specified by a number
followed by a letter. The number represents the lowest ambient air temperature at which the
capacitor may operate.
The letters represent upper limits of temperature variation ranges, having maximum values
specified in Table 1. The temperature categories cover the temperature range of −50 °C to
+55 °C.
The lowest ambient air temperature at which the capacitor may be operated should be chosen
from the five preferred values +5 °C, −5 °C, −25 °C, −40 °C, −50 °C.
For indoor use, a lower limit of −5 °C is normally applicable.
Table 1 is based on service conditions in which the capacitor does not influence the ambient
air temperature (for example outdoor installations).
Table 1 – Letter symbols for upper limit of temperature range
Symbol Ambient temperature
°C
Maximum Highest mean over any period of
24 h 1 year
A 40 30 20
B 45 35 25
C 50 40 30
D 55 45 35
The temperature values according to Table 1 can be found in the meteorological temperature
table covering the installation site.
Higher temperature values than those indicated in Table 1 can be considered in special
applications by mutual agreement between manufacturer and purchaser. In that case, the
temperature category should be indicated by the combination of minimum and maximum
temperature values, for example, −40/60.
If the capacitor influences the air temperature, the ventilation and/or choice of capacitor shall
be such that the Table 1 limits are maintained. The cooling air temperature in such an
installation shall not exceed the temperature limits of Table 1 by more than 5 °C.
Any combination of minimum and maximum values may be chosen for the standard temperature
category of a capacitor, for example −40/A or −5/C.
Preferred temperature categories are:
−40/A, −25/A, −5/A and −5/C.
4.2 Unusual service conditions
Unless otherwise agreed between manufacturer and purchaser, this document does not apply
to capacitors, the service conditions of which, in general, are incompatible with the
requirements of this document.
5 Test requirements
5.1 General
This clause gives the test requirements for capacitor units and, when specified, for capacitor
elements.
Supporting insulators, switches, instrument transformers, fuses, etc, shall be in accordance
with relevant IEC standards.
5.2 Test conditions
Unless otherwise specified for a particular test or measurement, the temperature of the
capacitor dielectric at the start of the test shall be in the range of +5 °C to +35 °C.
It may be assumed that the dielectric temperature is the same as the ambient temperature,
provided that the capacitor has been left in an unenergized state at constant ambient
temperature for an adequate period. When a correction has to be applied, the reference
temperature to be used is +20 °C, unless otherwise agreed between the manufacturer and the
purchaser.
The AC tests and measurements shall be carried out at a frequency of 50 Hz or 60 Hz ± 2 Hz,
independent of the rated frequency of the capacitor, if not otherwise specified.
6 Tests
6.1 Classification
6.1.1 General
The tests are classified as routine tests, type tests and acceptance tests.
6.1.2 Routine tests
The following tests are routine tests. For details, reference should be made to the relevant
clauses or subclauses.
a) Capacitance measurement and output calculation (see 6.2).
b) Measurement of the tangent of the loss angle (tan δ) of the capacitor (see 6.3).
c) Voltage test between terminals (see 6.4.1).
d) Voltage test between terminals and container (see 6.5.1).
e) Test of the internal discharge device (see 6.6).
f) Sealing test (see 6.7).
Routine tests shall have been carried out by the manufacturer on every capacitor before
delivery. The purchaser shall, on request, be supplied with a certificate detailing the results of
such tests.
In general, the indicated sequence of the tests is not mandatory.
6.1.3 Type tests
The following tests are type tests. For details, reference should be made to the relevant clauses
or subclauses:
a) Thermal stability test (see 6.8).
b) Measurement of the tangent of the loss angle (tan δ) of the capacitor at elevated
temperature (see 6.9).
c) Voltage test between terminals (see 6.4.2).
d) Voltage test between terminals and container (see 6.5.2).
e) Lightning impulse voltage test between terminals and container (see 6.10).
f) Discharge test (see 6.11).
g) Ageing test (see 6.12).
h) Destruction test (see 6.13).
i) Disconnecting test on internal fuses (see 6.14).
Type tests are carried out in order to ascertain that, as regards design, size, materials and
construction, the capacitor complies with the specified characteristics and operation
requirements detailed in this document.
Unless otherwise specified, every capacitor sample to which it is intended to apply the type test
shall first have withstood satisfactorily the application of all the routine tests.
The type tests shall have been carried out by the manufacturer, and the purchaser shall, on
request, be supplied with a certificate detailing the results of such tests.
The successful completion of each type test is also valid for units having the same rated voltage
and lower output, provided that they do not differ in any way that can influence the properties
to be checked by the test. It is not essential that all type tests be carried out on the same
capacitor sample.
The number of samples for the type test shall be subjected to agreement between the
manufacturer and user.
6.1.4 Acceptance tests
The routine and/or type tests, or some of them, may be repeated by the manufacturer in
connection with any contract by agreement with the purchaser. The kind of tests, the number
of samples that may be subjected to such repeated tests and the acceptance criteria shall be
subject to agreement between manufacturer and purchaser, and shall be stated in the contract.
6.2 Capacitance measurement and output calculation
6.2.1 Measuring procedure
The capacitance shall be measured at the voltage and the frequency chosen by the
manufacturer. The method used shall not include errors due to harmonics or to accessories
external to the capacitor to be measured such as reactors and blocking circuits in the measuring
circuit. The accuracy of the measuring method and the correlation with the values measured at
rated voltage and frequency shall be given.
The capacitance measurement shall be carried out after the voltage test between terminals
(see 6.4).
Measurement at a voltage between 0,9 and 1,1 times the rated voltage, and at a frequency
between 0,8 and 1,2 times the rated frequency, shall be performed on the capacitor used for
the thermal stability test (see 6.8) and the ageing test (see 6.12) before these tests, and may
be performed on other capacitors on request of the purchaser in agreement with the
manufacturer.
6.2.2 Capacitance tolerances
The capacitance shall not differ from the rated capacitance by more than
–5 % to +10 % for units and banks up to and including 100 kvar,
–5 % to +5 % for units and banks above 100 kvar.
The capacitance value is that measured under the conditions of 6.2.1.
In three-phase units, the ratio of maximum to minimum value of the capacitance measured
between any two line terminals shall not exceed 1,08.
NOTE A formula for calculation of the output of a three-phase capacitor from single-phase capacitance
measurement is given in Annex B.
6.3 Measurement of the tangent of the loss angle (tan δ) of the capacitor
6.3.1 Measuring procedure
The capacitor losses (tan δ) shall be measured at the voltage and the frequency chosen by the
manufacturer. The method used shall not include errors due to harmonics or to accessories
external to the capacitor to be measured, such as reactors and blocking circuits in the
measuring circuit. The accuracy of the measuring method and the correlation with the values
measured at rated voltage and frequency shall be given.
The measurement of the capacitor losses shall be carried out after the voltage test between
terminals (see 6.4).
Measurement at a voltage between 0,9 and 1,1 times the rated voltage and at a frequency
between 0,8 and 1,2 times the rated frequency shall be performed on the capacitor before the
thermal stability test (see 6.8), and may be performed on other capacitors on request of the
purchaser in agreement with the manufacturer.
The tan δ value of certain types of dielectric is a function of the energization time before the
measurement. In that case, test voltage and energization time should be agreed between
manufacturer and purchaser.
6.3.2 Loss requirements
The value of tan δ, measured in accordance with 6.3.1, shall not exceed the value declared by
the manufacturer for the temperature and voltage of the test, or the value agreed upon between
manufacturer and purchaser.
6.4 Voltage tests between terminals
6.4.1 Routine test
Every capacitor shall be subjected for 10 s to either the test in item a) or the test in item b). If
no prior agreement is reached, the choice is left to the manufacturer. During the test, neither
puncture nor flashover shall occur.
a) An AC test, the test voltage being:
U = 2,15 U
t N
The AC test shall be carried out with a substantially sinusoidal voltage.
b) A DC test, the test voltage being:
U = 4,3 U
t N
For polyphase capacitors, the test voltages should be adjusted as appropriate.
NOTE Operation of internal element fuses is permitted, provided the capacitance tolerances are still met and that
not more than two fuses have operated per unit.
6.4.2 Type test
Already performed during the routine test according to 6.4.1. Refer also to the third paragraph
of 6.1.3.
6.5 Voltage tests between terminals and container
6.5.1 Routine test
Units having all terminals insulated from the container shall be subjected to an AC voltage
applied between the terminals (joined together) and the container. The voltage to be
applied is 2U + 2 kV or 3 kV, whichever is the higher, for 10 s or 20 % higher for a
N
minimum time of 2 s.
If the units are intended to be connected directly to the aerial power line and by agreement
b
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