IEC 60143-1:2015

IEC 60143-1 ®
Edition 5.1 2023-11
CONSOLIDATED VERSION
INTERNATIONAL
STANDARD
NORME
INTERNATIONALE
colour
inside
Series capacitors for power systems –
Part 1: General
Condensateurs série destinés à être installés sur des réseaux –
Partie 1: Généralités
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IEC 60143-1 ®
Edition 5.1 2023-11
CONSOLIDATED VERSION
INTERNATIONAL
STANDARD
NORME
INTERNATIONALE
colour
inside
Series capacitors for power systems –
Part 1: General
Condensateurs série destinés à être installés sur des réseaux –
Partie 1: Généralités
INTERNATIONAL
ELECTROTECHNICAL
COMMISSION
COMMISSION
ELECTROTECHNIQUE
INTERNATIONALE
ICS 31.060.70 ISBN 978-2-8322-7807-9

IEC 60143-1 ®
Edition 5.1 2023-11
CONSOLIDATED VERSION
REDLINE VERSION
VERSION REDLINE
colour
inside
Series capacitors for power systems –
Part 1: General
Condensateurs série destinés à être installés sur des réseaux –
Partie 1: Généralités
– 2 – IEC 60143-1:2015+AMD1:2023 CSV
© IEC 2023
CONTENTS
FOREWORD . 6
1 Scope and object . 8
2 Normative references . 8
3 Terms and definitions . 9
4 Service conditions . 14
4.1 Normal service conditions . 14
4.2 Ambient air temperature categories . 15
4.3 Abnormal service conditions . 15
4.4 Abnormal power system conditions . 16
5 Quality requirements and tests . 16
5.1 Test requirements for capacitor units . 16
5.1.1 General . 16
5.1.2 Test conditions . 16
5.1.3 Voltage limits as established by overvoltage protector . 16
5.1.4 Determination of protective level voltage U and U . 18
pl lim
5.2 Classification of tests . 18
5.2.1 General . 18
5.2.2 Routine tests . 18
5.2.3 Type tests . 18
5.2.4 Special test (ageing test) . 19
5.3 Capacitance measurement (routine test) . 19
5.3.1 Measuring procedure . 19
5.3.2 Capacitance tolerance . 20
5.4 Capacitor loss measurement (routine test) . 20
5.4.1 Measuring procedure . 20
5.4.2 Loss requirements . 20
5.4.3 Losses in external fuses . 21
5.5 Voltage test between terminals (routine test) . 21
5.6 AC voltage test between terminals and container (routine test) . 21
5.7 Test on internal discharge device (routine test) . 21
5.8 Sealing test (routine test) . 21
5.9 Thermal stability test (type test) . 21
5.9.1 Measuring procedure . 21
5.9.2 Capacitor loss measurement . 23
5.10 AC voltage test between terminals and container (type test) . 23
5.11 Lightning impulse voltage test between terminals and container (type test) . 23
5.12 Cold duty test (type test) . 24
5.13 Discharge current test (type test) . 25
6 Insulation level . 26
6.1 Insulation voltages . 26
6.1.1 Standard values . 26
6.1.2 Insulation to earth and between phases . 26
6.1.3 Insulation levels for insulators and equipment on the platform . 26
6.2 Creepage distance . 33
6.3 Air clearances . 34
7 Overloads, overvoltages and duty cycles . 38

© IEC 2023
7.1 Currents . 38
7.2 Transient overvoltages . 38
7.3 Duty cycles . 39
8 Safety requirements . 39
8.1 Discharge device . 39
8.2 Container connection . 39
8.3 Protection of the environment . 40
8.4 Other safety requirements . 40
9 Markings and instruction books. 40
9.1 Markings of the unit . 40
9.1.1 Rating plate . 40
9.1.2 Warning plate . 41
9.2 Markings of the bank . 41
9.2.1 Instruction sheet or rating plate . 41
9.2.2 Warning plate . 41
9.3 Instruction book . 41
10 Guide for selection of ratings, installation and operation . 42
10.1 General . 42
10.2 Reactance per line, rated reactance per bank and number of modules per
bank . 42
10.2.1 Capacitive reactance per line . 42
10.2.2 Number of series capacitor banks in a transmission line . 43
10.2.3 Number of modules in a capacitor bank . 43
10.2.4 Future requirements for series capacitors . 44
10.3 Current ratings for the bank . 44
10.3.1 General . 44
10.3.2 Typical bank overload and swing current capabilities . 45
10.3.3 Analysis to determine the continuous and emergency overload current
rating . 46
10.3.4 Analysis to determine the swing current rating . 46
10.4 Overvoltage protection requirements . 46
10.5 Voltage limitations during power system faults . 47
10.5.1 General . 47
10.5.2 Voltage limitation when the inductance between the primary overvoltage
protector and the capacitors is not significant . 47
10.5.3 Voltage limitation when the inductance between the primary overvoltage
protector and the capacitors is significant . 48
10.6 Protective and switching devices . 48
10.6.1 Capacitor fusing . 48
10.6.2 Other devices . 48
10.6.3 Connection diagrams . 49
10.7 Choice of insulation level . 49
10.7.1 Normal cases. 49
10.7.2 Altitude exceeding 1 000 m . 49
10.8 Long line correction . 50
10.9 Other application considerations . 51
10.9.1 General . 51
10.9.2 Ferro-resonance . 51
10.9.3 Sub-synchronous resonance . 51

– 4 – IEC 60143-1:2015+AMD1:2023 CSV
© IEC 2023
10.9.4 Relay protection of the power system . 51
10.9.5 Attenuation of carrier-frequency transmission . 52
10.9.6 Non-transposed transmission lines . 52
10.9.7 Power system harmonic currents . 52
10.9.8 TRV across line circuit-breakers . 52
10.9.9 Delayed line current zero crossing . 53
10.9.10 Prolonged secondary arc current . 53
Annex A (normative) Test requirements and application guide for external fuses and
units to be externally fused . 54
A.1 Overview. 54
A.2 Purpose . 54
A.3 Terms employed in Annex A . 54
A.4 Performance requirements . 54
A.5 Tests . 55
A.5.1 Tests on fuses . 55
A.5.2 Type tests on capacitor container . 55
A.6 Guide for coordination of fuse protection . 55
A.6.1 General . 55
A.6.2 Protection sequence . 55
A.7 Choice of fuses . 56
A.7.1 General . 56
A.7.2 Non current-limiting fuses . 56
A.7.3 Current-limiting fuses. 56
A.8 Information needed by the user of the fuses . 56
Annex B (informative) Economic evaluation of series capacitor bank losses . 57
Annex C (informative) Capacitor bank fusing and unit arrangement . 58
C.1 General . 58
C.2 Internally fused capacitor bank . 58
C.3 Externally fused capacitor bank . 58
C.4 Fuseless capacitor bank . 59
Annex D (informative) Examples of typical connection diagrams for large series
capacitor installations for transmission lines . 61
Annex E (informative) Precautions to be taken to avoid pollution of the environment by

polychlorinated biphenyls . 62
Bibliography . 63

Figure 1 – Typical nomenclature of a series capacitor installation . 12
Figure 2 – Classification of overvoltage protection . 17
Figure 3 – Time and amplitude limits for an overvoltage period waveform . 25
Figure 4 – Air clearance versus a.c. power frequency withstand voltage . 38
Figure 5 – Typical current-time profile of an inserted capacitor bank following the fault
and clearing of parallel line . 45
Figure C.1 – Typical connections between capacitor units in a segment or phase . 59
Figure C.2 – Typical connections between elements within a capacitor unit . 60
Figure D.1 – Diagrams for smaller banks . 61

Table 1 – Letter symbols for upper limit of temperature range . 15

© IEC 2023
Table 2 – Ambient air temperature in thermal stability test . 22
Table 3 – Standard insulation levels for range I (1 kV < U ≤ 245 kV) . 29
m
Table 4 – Standard insulation levels for range II (U > 245 kV) (1 of 2) . 30
m
Table 5 – Typical insulation levels for platform-to-ground insulators (1 of 2) . 32
Table 6 – Specific creepage distances . 34
Table 7 – Correlation between standard lightning impulse withstand voltages and
minimum air clearances . 36
Table 8 – Correlation between standard switching impulse withstand voltages and

minimum phase-to-earth air clearances. 37
Table 9 – Correlation between standard switching impulse withstand voltages and
minimum phase-to-phase air clearances . 37
Table 10 – Typical bank overload and swing current capabilities . 45

– 6 – IEC 60143-1:2015+AMD1:2023 CSV
© IEC 2023
INTERNATIONAL ÉLECTROTECHNICAL COMMISSION
____________
SERIES CAPACITORS FOR POWER SYSTEMS –

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
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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
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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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5) IEC itself does not provide any attestation of conformity. Independent certification bodies provide conformity
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6) All users should ensure that they have the latest edition of this publication.
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8) Attention is drawn to the Normative references cited in this publication. Use of the referenced publications is
indispensable for the correct application of this publication.
9) Attention is drawn to the possibility that some of the elements of this IEC Publication may be the subject of
patent rights. IEC shall not be held responsible for identifying any or all such patent rights.
This consolidated version of the official IEC Standard and its amendment has been
prepared for user convenience.
IEC 60143-1 edition 5.1 contains the fifth edition (2015-06) [documents 33/578/FDIS and
33/580/RVD], its corrigendum (2017-04), and its amendment 1 (2023-11) [documents
33/690/CDV and 33/693/RVC].
In this Redline version, a vertical line in the margin shows where the technical content
is modified by amendment 1. Additions are in green text, deletions are in strikethrough
red text. A separate Final version with all changes accepted is available in this
publication.
© IEC 2023
International Standard IEC 60143-1 has been prepared by IEC technical committee 33: Power
capacitors and their applications.
This fifth edition constitutes a technical revision.
The main change with respect to the previous edition is that the endurance test has been
replaced by an ageing test because voltage cycling is already performed in the cold duty test.
The guide section has been expanded regarding long line correction and altitude correction.
In addition the insulation tables and references to other standards have been updated.
This publication has been drafted in accordance with the ISO/IEC Directives, Part 2.
A list of all parts in the IEC 60143 series, published under the general title Series capacitors
for power systems, can be found on the IEC website.
The committee has decided that the contents of this document and its amendment 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,
• replaced by a revised edition, or
• amended.
IMPORTANT – The 'colour inside' logo on the cover page of this publication 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.
– 8 – IEC 60143-1:2015+AMD1:2023 CSV
© IEC 2023
SERIES CAPACITORS FOR POWER SYSTEMS –

Part 1: General
1 Scope and object
This part of IEC 60143 applies both to capacitor units and capacitor banks intended to be
used connected in series with an a.c. transmission or distribution line or circuit forming part of
an a.c. power system having a frequency of 15 Hz to 60 Hz.
The primary focus of this standard is on transmission application.
The series capacitor units and banks are usually intended for high-voltage power systems.
This standard is applicable to the complete voltage range.
This standard does not apply to capacitors of the self-healing metallized dielectric type.
The following capacitors, even if connected in series with a circuit, are excluded from this
standard:
– capacitors for inductive heat-generating plants (IEC 60110-1);
– capacitors for motor applications and the like (IEC 60252 (all parts));
– capacitors to be used in power electronics circuits (IEC 61071);
– capacitors for discharge lamps (IEC 61048 and IEC 61049).
For standard types of accessories such as insulators, switches, instrument transformers,
external fuses, etc. see the pertinent IEC standard.
NOTE 1 Additional requirements for capacitors to be protected by internal fuses, as well as the requirements for
internal fuses, are found in IEC 60143-3. See also Annex C.
NOTE 2 Additional requirements for capacitors to be protected by external fuses, as well as the requirements for
external fuses, are found in Annex A and Annex C.
NOTE 3 A separate standard for series capacitor accessories (spark-gaps, varistors, discharge reactors, current-
limiting damping reactors, damping resistors, circuit-breakers, etc.), IEC 60143-2, has been revised and was
completed in 2012. A separate standard for internal fuses for series capacitors, IEC 60143-3 has been revised and
was completed in 2013.
NOTE 4 Some information regarding fuseless capacitor units and fuseless capacitor banks is found in Annex C.
The object of this standard is:
– to formulate uniform rules regarding performance, testing and rating;
– to formulate specific safety rules;
– to serve as a guide for installation and operation.
2 Normative references
The following documents, in whole or in part, are normatively referenced in this document and
are indispensable for its application. For dated references, only the edition cited applies. For
undated references, the latest edition of the referenced document (including any
amendments) applies.
NOTE If there is a conflict between this standard and a standard listed below, the text of IEC 60143-1 prevails.

© IEC 2023
IEC 60050 (all parts), International Electrotechnical Vocabulary (available at
www.electropedia.org)
IEC 60060-1:2010, High-voltage test techniques – Part 1: General definitions and test
requirements
IEC 60071-1:2006, Insulation co-ordination – Part 1: Definitions, principles and rules
IEC 60071-2:1996, Insulation co-ordination – Part 2: Application guide
IEC 60143-2:2012, Series capacitors for power systems – Part 2: Protective equipment for
series capacitor banks
IEC 60143-3:1998, Series capacitors for power systems – Part 3: Internal fuses
IEC 60143-4: 2010 Series capacitors for power systems – Part 4: Thyristor controlled series
capacitors
IEC 60549:2013, High-voltage fuses for the external protection of shunt capacitors
IEC 60871-1: 2014 Shunt capacitors for a.c power systems having a rated voltage above
1000V – Part 1: General
IEC 62271-1:2007, High-voltage switchgear and controlgear – Part 1: Common specifications
IEEE Std. 693:1997, IEEE Recommended Practice for Seismic Design of Substations
3 Terms and definitions
For the purposes of this document, the following terms and definitions apply.
3.1
ambient air temperature (for capacitors)
temperature of air at the proposed location of the capacitor installation
3.2
bypass switch
device such as a switch or circuit-breaker used in parallel with a series capacitor and its
overvoltage protector to shunt line current for some specified time or continuously
Note 1 to entry: This device shall also have the capability of bypassing the capacitor during specified power
system fault conditions. The operation of the device is initiated by the capacitor bank control, remote control or by
an operator. The device may be mounted on the platform or on the ground near the platform. Besides bypassing
the capacitor, this device shall also have the capability of inserting the capacitor into a circuit carrying a specified
level of current.
3.3
capacitor
word used when it is not necessary to distinguish between the different meanings of the words
capacitor unit and the assembly of capacitors associated with a segment
3.4
capacitor unit
unit
assembly of one or more capacitor elements in the same container with terminals brought out

– 10 – IEC 60143-1:2015+AMD1:2023 CSV
© IEC 2023
[SOURCE: IEC 60050-436:1990, 436-01-04]
3.5
(capacitor) element
device consisting essentially of two electrodes separated by a dielectric
[SOURCE: IEC 60050-436:1990, 436-01-03]
3.6
capacitor losses
active power dissipated in the capacitor
Note 1 to entry: All loss-producing components should be included. For a unit, this includes losses from the
dielectric, discharge device, internal fuses (if applicable) and internal connections. For the bank, this includes
losses from the units, external fuses (if applicable) and busbars. See Annex B for additional discussion.
[SOURCE: IEC 60050-436:1990, 436-04-10]
3.7
cooling air temperature
temperature of cooling air measured at the hottest position in the capacitor assembly of a
segment, under rated current and 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.
3.8
degree of compensation
k
degree of series compensation, k (of a line section) is
k = 100 (X / X ) %
c L
where
is the capacitive reactance of the series capacitor;
X
c
X is the total positive sequence inductive reactance of the transmission line section on which
L
the series capacitor is applied.
3.9
discharge device (of a capacitor)
device connected across the terminals of the capacitor or built into the capacitor unit, capable
of reducing the residual voltage across the capacitor effectively to zero after the capacitor has
been disconnected from the supply
Note 1 to entry: Further requirements on the size of the discharge device are found in 8.1.
[SOURCE: IEC 60050-436:1990, 436-03-15, modified (modified definition, addition of Note 1
to entry)]
3.10
external fuse (of a capacitor)
fuse connected in series with a capacitor unit or with a group of parallel units
3.11
fuseless capacitor bank
capacitor bank without any fuses, internal or external, constructed of parallel strings of
capacitor units. Each string consists of capacitor units connected in series
Note 1 to entry: See Annex C for an explanation of “string”.

© IEC 2023
3.12
highest voltage of a three-phase system
highest r.m.s. phase-to-phase voltage which occurs under normal operating conditions at any
time and at any point of the system
Note 1 to entry: It excludes voltage transients (such as those due to system switching) and temporary voltage
variations due to abnormal system conditions (such as due to faults or sudden disconnection of large loads).
3.13
highest voltage for equipment
U
m
highest r.m.s. value of phase-to-phase voltage for which the equipment is designed in respect
of its insulation as well as other characteristics which relate to this voltage in the relevant
equipment standards
Note 1 to entry: This voltage is the maximum value of the highest voltage of the system for which the equipment
may be used.
[SOURCE: IEC 60050-604:1987, 604-03-01]
3.14
insulation level
U
i
non-simultaneous combination of test voltages (power-frequency (U ) or switching impulse,
ipf
and lightning impulse) which characterizes the insulation of the capacitor with regard to its
capability of withstanding the electric stresses between terminals and earth, between phases
and between terminals and metalwork (e.g. platform) not at earth potential
3.15
internal fuse of a capacitor
fuse connected inside a capacitor unit, in series with an element or group of elements
[SOURCE: IEC 60050-436:1990, 436-03-16]
3.16
limiting voltage
U
lim
maximum peak of the power frequency voltage occurring between capacitor unit terminals
immediately before or during operation of the overvoltage protector, divided by 2
SEE: 5.1.4
Note 1 to entry: This voltage appears either during conduction of the varistor or immediately before ignition of the
spark gap.
3.17
line terminal
terminal to be connected to the power system
[SOURCE: IEC 60050-436:1990, 436-03-01, modified (modified definition)]
3.18
module (of a series capacitor)
switchable step of a series capacitor consisting of identical segments in each phase (see
Figure 1), which furthermore are also equipped with provisions for a common operation of the
bypass switch of each of these segments
Note 1 to entry: The bypass switch of a module is normally operated on a three-phase basis. However, in some
applications for protection purposes, the bypass switch may be required to temporarily operate on an individual
phase basis.
– 12 – IEC 60143-1:2015+AMD1:2023 CSV
© IEC 2023
Note 2 to entry: Figure 1 shows a typical nomenclature of a series capacitor installation.
SC installation
SC
Module 1 Module N
bank
9 9
Phase A
2-7
11 11
Segment A1 Segment AN
9 9
Phase B
Segment B1
Segment BN
9 9
Phase C
11 11
Segment C1
Segment CN
IEC
Key
1 assembly of capacitor units
2-7 main protective equipment (Figure 2c) and Annex D)
9 isolating disconnector
10 bypass disconnector
11 earth switch
NOTE 1 A SC Installation includes a SC Bank plus 9, 10 and 11.
NOTE 2 Most series capacitors are configured with a single module, unless the reactance and current
requirements result in a voltage across the bank that is impractical for the supplier to achieve with one module.
Normally each module has its own bypass switch, but a common bypass switch may be used for more than one
module. See clause 10.2.3 for additional details.
Figure 1 – Typical nomenclature of a series capacitor installation
3.19
overvoltage protector (of a series capacitor)
quick-acting device (usually MOV or a self triggered spark gap) which limits the voltage
across the capacitor to a permissible value when that value would otherwise be exceeded as
a result of a circuit fault or other abnormal power system conditions
3.20
power frequency withstand voltage
U
ipf
wet power frequency withstand voltage of bushings and insulators
3.21
protective level
U
pl
magnitude of the maximum peak of the power frequency voltage appearing across the
overvoltage protector during a power system fault

© IEC 2023
Note 1 to entry: The protective level may be expressed in terms of the actual peak voltage across a segment or in
terms of the per unit of the peak of the rated voltage across the capacitor (see 5.1.4, 10.4 and 10.5). This voltage
appears either during conduction of the varistor or immediately before ignition of the spark gap.
3.22
rated capacitance (of a capacitor)
C
N
capacitance value for which the capacitor has been designed
3.23
rated current of a capacitor
I
N
r.m.s. value of the alternating current for which the capacitor has been designed
[SOURCE: IEC 60050-436:1990, 436-01-13]
3.24
rated frequency (of a capacitor)
f
N
frequency of the system in which the capacitor is intended to be used
[SOURCE: IEC 60050-436:1990, 436-01-14, modified (modified definition)]
3.25
rated output (of a capacitor)
Q
N
reactive power derived from rated reactance and rated current
Note 1 to entry: For the bank, the rated three-phase reactive power rating in Mvar (Q ) is defined by the equation:
N
× X
Q = 3 × I
N N N
where
I is the rated current, in kA;
N
X is the rated reactance, in Ω.
N
3.26
rated reactance (of capacitor)
X
N
reactance of each phase of the series capacitor at rated frequency and 20 °C dielectric
temperature
3.27
rated voltage (of the bank)
power system phase-to-phase voltage for which the phase-to-ground insulation system is
designed
3.28
rated voltage (of a capacitor)
U
N
r.m.s. value of the voltage between the terminals, derived from rated reactance and rated
current U = X × I
N N N
3.29
residual voltage (of a capacitor)
voltage remaining between terminals of a capacitor at a given time following disconnection of
the supply
– 14 – IEC 60143-1:2015+AMD1:2023 CSV
© IEC 2023
3.30
segment (of a series capacitor)
single-phase assembly of groups of capacitors which has its own voltage-limiting devices and
relays to protect the capacitors from overvoltages and overloads
SEE: Figure 1
Note 1 to entry: Segments are not normally separated by isolating disconnectors. More than one segment can be
on the same insulated platform.
3.31
series capacitor bank (or bank)
three-phase assembly of capacitors with the associated protection and insulated support
structure
Note 1 to entry: The bank may include one or more modules (see Figure 1).
3.32
series capacitor installation
series capacitor bank and its accessories including the bypass and isolating disconnectors
[SOURCE: IEC 60050-436:1990, 436-01-07, modified (addition of "including the bypass and
isolating connectors")]
3.33
steady-state condition
thermal equilibrium attained by the capacitor at constant output and at constant ambient air
temperature
3.34
sub-segment
portion of a segment that includes a single-phase assembly of capacitor units an an
associated protective device, discharge current limiting an damping equipment, and selected
protection and control functions, but does not have a dedicated by-pass switch
3.35
tangent of loss angle (of a capacitor)
tan δ
ratio between the equivalent series resistance and the capacitive reactance of a capacitor at
specified sinusoidal alternating voltage and frequency
Note 1 to entry: Tangent of loss angle can also be expressed as the capacitor losses divided by the reactive
power of the capacitor.
3.36
varistor coordinating current
magnitude of the maximum peak of power frequency varistor current associated with the
protective level
Note 1 to entry: The varistor coordinating current waveform is considered to
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