Series capacitors for power systems - Part 3: Internal fuses

IEC 60143-3:2015 applies to internal fuses designed to isolate faulty capacitor elements, to allow operation of the remaining parts of that capacitor unit and the bank in which the capacitor unit is connected. Such fuses are not a substitute for a switching device such as a circuit-breaker, or for external protection of the capacitor bank, or any part thereof. The object of this part of IEC 60143 is:
- to formulate requirements regarding performance and testing;
- to provide a guide for coordination of fuse and bank protection. This second edition cancels and replaces the first edition published in 1998. This edition constitutes a technical revision. This edition includes the following significant technical changes with respect to the previous edition: The test procedure has been largely simplified. Keywords: faulty capacitor elements, fuse and bank protection

Condensateurs série destinés à être installés sur des réseaux - Partie 3: Fusibles internes

L'IEC 60143-3:2015 s'applique aux fusibles internes destinés à isoler les éléments en défaut d'un condensateur, et permettre ainsi le maintien en service de la partie saine de l'unité de condensateur et de la batterie à laquelle cette unité est raccordée. Ils ne sont pas destinés à se substituer à un dispositif de coupure, par exemple un disjoncteur ou une protection externe de la batterie de condensateurs ou une partie de celle-ci. La présente partie de l'IEC 60143 a pour objet:
- de formuler des exigences relatives aux performances et aux essais;
- de fournir un guide pour la coordination de la protection par fusibles et de la protection de la batterie. Cette deuxième édition annule et remplace la première édition paru e en 1998. Cette édition constitue une révision technique. Cette édition inclut les modifications techniques majeures suivantes par rapport à l'édition précédente: Les procédures d'essai ont été simplifiée. Mots clés: éléments en défaut d'un condensateur, protection par fusibles et de la protection de la batterie

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Publication Date
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Current Stage
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IEC 60143-3
Edition 2.0 2015-06
INTERNATIONAL
STANDARD
NORME
INTERNATIONALE
Series capacitors for power systems –
Part 3: Internal fuses
Condensateurs série destinés à être installés sur des réseaux –
Partie 3: Fusibles internes
IEC 60143-3:2015-06(en-fr)
---------------------- Page: 1 ----------------------
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---------------------- Page: 2 ----------------------
IEC 60143-3
Edition 2.0 2015-06
INTERNATIONAL
STANDARD
NORME
INTERNATIONALE
Series capacitors for power systems –
Part 3: Internal fuses
Condensateurs série destinés à être installés sur des réseaux –
Partie 3: Fusibles internes
INTERNATIONAL
ELECTROTECHNICAL
COMMISSION
COMMISSION
ELECTROTECHNIQUE
INTERNATIONALE
ICS 31.060.70 ISBN 978-2-8322-2715-2

Warning! Make sure that you obtained this publication from an authorized distributor.

Attention! Veuillez vous assurer que vous avez obtenu cette publication via un distributeur agréé.

® Registered trademark of the International Electrotechnical Commission
Marque déposée de la Commission Electrotechnique Internationale
---------------------- Page: 3 ----------------------
– 2 – IEC 60143-3:2015 © IEC 2015
CONTENTS

FOREWORD ......................................................................................................................... 3

1 Scope ............................................................................................................................ 5

2 Normative references..................................................................................................... 5

3 Terms and definitions .................................................................................................... 5

4 Performance requirements ............................................................................................. 5

4.1 General ................................................................................................................. 5

4.2 Disconnecting requirements .................................................................................. 6

4.3 Withstand requirements ......................................................................................... 6

5 Tests ............................................................................................................................. 7

5.1 Routine tests ......................................................................................................... 7

5.1.1 General ......................................................................................................... 7

5.1.2 Discharge test ................................................................................................ 7

5.2 Type tests ............................................................................................................. 7

5.2.1 General ......................................................................................................... 7

5.2.2 Discharge test on fuses .................................................................................. 7

5.2.3 Disconnecting test on fuses ............................................................................ 8

5.2.4 Voltage test after opening the container .......................................................... 8

Annex A (normative) Test procedures for the disconnecting test on internal fuses ................. 9

A.1 General ................................................................................................................. 9

A.2 Test procedure – Mechanical puncture of the element ............................................ 9

Annex B (informative) Guide for coordination of fuse protection .......................................... 10

B.1 General ............................................................................................................... 10

B.2 Protection sequence ............................................................................................ 10

Bibliography ....................................................................................................................... 11

---------------------- Page: 4 ----------------------
IEC 60143-3:2015 © IEC 2015 – 3 –
INTERNATIONAL ELECTROTECHNICAL COMMISSION
____________
SERIES CAPACITORS FOR POWER SYSTEMS –
Part 3: Internal fuses
FOREWORD

1) The International Electrotechnical Commission (IEC) is a worldwide organization for standardization comprising

all national electrotechnical committees (IEC National Committees). The object of IEC is to promote

international co-operation on all questions concerning standardization in the electrical and electronic fields. To

this end and in addition to other activities, IEC publishes International Standards, Technical Specifications,

Technical Reports, Publicly Available Specifications (PAS) and Guides (hereafter referred to as “IEC

Publication(s)”). Their preparation is entrusted to technical committees; any IEC National Committee interested

in the subject dealt with may participate in this preparatory work. International, governmental and non-

governmental organizations liaising with the IEC also participate in this preparation. IEC collaborates closely

with the International Organization for Standardization (ISO) in accordance with conditions determined by

agreement between the two organizations.

2) The formal decisions or agreements of IEC on technical matters express, as nearly as possible, an international

consensus of opinion on the relevant subjects since each technical committee has representation from all

interested IEC National Committees.

3) IEC Publications have the form of recommendations for international use and are accepted by IEC National

Committees in that sense. While all reasonable efforts are made to ensure that the technical content of IEC

Publications is accurate, IEC cannot be held responsible for the way in which they are used or for any

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between any IEC Publication and the corresponding national or regional publication shall be clearly indicated in

the latter.

5) IEC itself does not provide any attestation of conformity. Independent certification bodies provide conformity

assessment services and, in some areas, access to IEC marks of conformity. IEC is not responsible for any

services carried out by independent certification bodies.

6) All users should ensure that they have the latest edition of this publication.

7) No liability shall attach to IEC or its directors, employees, servants or agents including individual experts and

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) 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 60143-3 has been prepared by IEC technical committee 33: Power

capacitors and their applications.

This second edition cancels and replaces the first edition published in 1998. This edition

constitutes a technical revision.

This edition includes the following significant technical changes with respect to the previous

edition:
The test procedure has been largely simplified.
---------------------- Page: 5 ----------------------
– 4 – IEC 60143-3:2015 © IEC 2015
The text of this standard is based on the following documents:
FDIS Report on voting
33/577/FDIS 33/579/RVD

Full information on the voting for the approval of this standard can be found in the report on

voting indicated in the above table.

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 publication will remain unchanged until

the stability date indicated on the IEC website under "http://webstore.iec.ch" in the data

related to the specific publication. At this date, the publication will be
• reconfirmed,
• withdrawn,
• replaced by a revised edition, or
• amended.
---------------------- Page: 6 ----------------------
IEC 60143-3:2015 © IEC 2015 – 5 –
SERIES CAPACITORS FOR POWER SYSTEMS –
Part 3: Internal fuses
1 Scope

This part of IEC 60143 applies to internal fuses designed to isolate faulty capacitor elements,

to allow operation of the remaining parts of that capacitor unit and the bank in which the

capacitor unit is connected. Such fuses are not a substitute for a switching device such as a

circuit-breaker, or for external protection of the capacitor bank, or any part thereof.

The object of this part of IEC 60143 is:
– to formulate requirements regarding performance and testing;
– to provide a guide for coordination of fuse and bank protection.

NOTE External fuses for series capacitors are treated in IEC 60143-1:2004, Annex A: "Test requirements and

application guide for external fuses and units to be externally fused".
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.
IEC 60143-1:2004, Series capacitors for power systems – Part 1: General

IEC 60143-2:2012, Series capacitors for power systems – Part 2: Protective equipment for

series capacitor banks
3 Terms and definitions

For the purposes of this document, the terms and definitions contained in IEC 60143-1 and

IEC 60143-2, as well as the following, apply.
3.1
rated voltage of a capacitor element U

r.m.s. value of the alternating voltage for which the capacitor element has been designed

4 Performance requirements
4.1 General

The fuse is connected in series with the element(s) which the fuse is intended to isolate if the

element(s) becomes faulty. The range of currents and voltages for the fuse is therefore

dependent on the capacitor design, and in some cases also on the design of the bank in

which the fuse is connected.

The operation of an internal fuse is in general determined by one or both of the two following

factors:
---------------------- Page: 7 ----------------------
– 6 – IEC 60143-3:2015 © IEC 2015

– the discharge energy from elements or units connected in parallel with the faulty element

or unit;
– the power-frequency fault current.
4.2 Disconnecting requirements

The fuse shall enable the faulty element to be disconnected when electrical breakdown of

elements occurs in a voltage range, in which u is the lowest, and u is the highest

1 2

(instantaneous) value of the voltage between the terminals of the unit at the instant of fault.

The recommended values for u and u are the following:
1 2
u = 0,5 2 U
1 N
u = 2 U
2 lim
For u , other values can be agreed upon between purchaser and manufacturer.
The u value is of a transient nature.

The u and u values above are based on the voltage that may normally occur across the

1 2
capacitor unit terminals at the instant of electrical breakdown of the element.

The purchaser shall specify if the u value differs from the stated one. If so, the value stated

in 3.2.3.1 shall be changed accordingly.

The u value cannot be exceeded due to the overvoltage protector. A voltage lower than the

u value can occur in service, but breakdowns are unlikely to take place under these

conditions.
4.3 Withstand requirements

4.3.1 After operation, the gap in the blown fuse shall withstand full element voltage, plus

any unbalance voltage due to fuse action, and any short-time transient overvoltages normally

experienced during the life of the capacitor.

4.3.2 Throughout the life of the capacitor, the fuse shall be capable of carrying

continuously a current equal to or greater than the rated capacitor unit current (including

harmonics if applicable), divided by the number of parallel fused paths. In addition, the fuse

shall withstand the working currents given in 7.1 and 10.3 of IEC 60143-1:2004.

4.3.3 The fuses shall be capable of withstanding the high-amplitude, high-frequency

discharge currents due to operation of the overvoltage protector and/or the bypass switch,

expected during the life of the capacitor.
4.3.4 The fuse connected to the undamaged element(s) shall be able to carry the
discharge currents due to the breakdown of element(s).

4.3.5 The fuse shall be able to carry the currents due to short-circuit faults on the bank

external to the unit(s) occurring within the voltage range in accordance with 2.2.

4.3.6 The fuse shall be capable of withstanding the high-amplitude, high-frequency

discharge current that will arise as a consequence of a flashover to platform fault or a varistor

failure.
---------------------- Page: 8 ----------------------
IEC 60143-3:2015 © IEC 2015 – 7 –
5 Tests
5.1 Routine tests
5.1.1 General

The fuses shall be able to withstand all routine tests of the capacitor unit in accordance with

IEC 60143-1.
5.1.2 Discharge test

Capacitors having internal fuses shall be subjected to one short-circuit discharge test, from a

(= 1,2 × 2 × U ), through a gap situated as closely as possible to the
d.c. voltage of 1,7 U
N N
capacitor, without any additional impedance in the circuit.

The capacitance shall be measured before and after the discharge test. The difference

between the two measurements shall be less than an amount corresponding to one internal

fuse operation.

The discharge test may be made before or after the voltage test between terminals (see 5.5 of

IEC 60143-1:2004). However, if it is made after the voltage test between terminals, a

capacitance measurement at rated voltage shall be made afterwards to detect fuse operation.

It is permitted that a d.c. charging voltage be generated by initially energizing with an a.c.

voltage of 1,7 U peak value and disconnecting at a current zero. The capacitor is then

immediately discharged from this peak value. Alternatively, if the capacitor is disconnected at

a slightly higher voltage than 1,7 U , the discharge may be delayed until the discharge

resistor reduces the voltage to 1,7 U .
5.2 Type tests
5.2.1 General

The fuses shall be able to withstand all type tests of the capacitor unit(s) in accordance with

IEC 60143-1.
The unit(s) shall have passed all routine tests stated in IEC 60143-1.

The disconnecting test on fuses (see 3.2.3) shall be performed either on one complete

capacitor unit or, at the choice of the manufacturer, on two units, one unit being tested at the

lower voltage limit, and one unit at the upper voltage limit, in accordance with 3.2.3.1.

NOTE Due to testing, measuring and safety circumstances, it may be necessary to make some modifications to

the unit(s) under test; for example those indicated in Annex A. See also the different test methods given in

Annex A.

Type tests are considered valid if they are performed on capacitor(s) of a design identical with

that of the capacitor offered, or on a capacitor(s) of a design that does not differ from it in any

way that might affect the properties to be checked by the type tests.
5.2.2 Discharge test on fuses

The fuses shall be subjected to the discharge test stated in 5.13 of IEC 60143-1:2004.

To prove that the fuses have not operated, a capacitance measurement shall be made before

and after the test. A measuring method shall be used that is sufficiently sensitive to detect the

capacitance change caused by one blown fuse.
---------------------- Page: 9 ----------------------
– 8 – IEC 60143-3:2015 © IEC 2015
5.2.3 Disconnecting test on fuses
5.2.3.1 Test procedures

The disconnecting test on fuses shall be performed at the lower a.c. test voltage of 0,5 × U ,

and at the upper a.c. test voltage of 1,1 × U , where 1,1 is a test factor. The tests may be

lim
performed on two different units, one for each level.

NOTE 1 For the upper a.c. test voltage, the discharge energy of parallel elements will normally blow the fuse,

whereas at the lower a.c. test voltage, a power-frequency current is normally required to blow the fuse.

Certain test methods are indicated in Annex A.

If the test is carried out with d.c., the test voltage shall be 2 times the corresponding a.c.

test voltage.

NOTE 2 Normally the dielectric would only withstand a voltage of 2.5 U for a very limited period of time.

Therefore a test with d.c. is in most cases to be preferred.

NOTE 3 If the test is carried out with a.c., the triggering of the element failure with a voltage peak will not be

necessary for the test at the lower voltage limit.

NOTE 4 The voltage u stated in 2.2 is the maximum voltage that the unit can be exposed to during service.

However the disconnecting test is performed at 1,1 times that voltage.
5.2.3.2 Capacitance measurement

After the test, the capacitance shall be measured to prove that the fuse(s) has (have) blown.

A measuring method shall be used that is sufficiently sensitive to detect the capacitance

change caused by one blown fuse.
5.2.3.3 Inspection of the unit
No significant deformation of the container shall be apparent.

After opening the container, a check shall be made to ensure that at lower and upper voltage

limit:
a) no severe deformation of sound fuses is apparent;

b) no more than one additional fuse (or one-tenth of fused elements directly in parallel) has

been damaged (see Note 1 of Clause A.1).

NOTE 1 A small amount of blackening of the impregnant will not affect the quality of the capacitor.

NOTE 2 Dangerous trapped charges may be present on elements disconnected either by operated fuses or by

damage to their connections. All elements will be discharged with great care.
5.2.4 Voltage test after opening the container

A d.c. test voltage equal to 1,7 × U shall be applied for 10 s across the broken-down

lim

element and the gap in its blown fuse. During the test, the gap shall be in the impregnant.

No breakdown over the fuse gap or between any part of the fuse and any other part of the unit

is allowed.

The test can be replaced by an a.c. test before opening of the unit. The test voltage between

the terminals is calculated using the capacitance ratio such that the voltage across the

breakdown element and the gap in its blown fuse is the value given in 3.2.4, divided by 2 .

---------------------- Page: 10 ----------------------
IEC 60143-3:2015 © IEC 2015 – 9 –
Annex A
(normative)
Test procedures for the disconnecting test on internal fuses
A.1 General

The test procedure described in A.2 or an alternative method agreed upon between the

manufacturer and the purchaser, shall be used.

If no agreement has been reached, the choice is left to the manufacturer: see also the note

in 3.2.1.

The capacitor voltage and current shall be recorded during the test to verify that the fuse has

disconnected correctly.

To verify the current-limiting behaviour of the fuses when tested at the upper voltage limit, the

voltage drop, excluding transient, across the blown fuse shall not exceed 30 %.

If the fuse does not fulfil this requirement, precautions shall be taken to make certain that the

parallel stored energy and the power-frequency fault current available from the system are

representative of service conditions. A test shall then be made to demonstrate the satisfactory

operation of the fuse.

At the upper voltage limit, one additional fuse (or one-tenth of the fused elements directly in

parallel) connected to a sound element(s) is allowed to be damaged.

The test voltage should be maintained some seconds after a breakdown, to ensure that the

fuse has disconnected correctly, unaided by disconnection of the power supply.

Precautions should be taken when performing this test against the possible explosion of a

capacitor unit and the explosive projection of the nail.

Coordination of the element failure with an a.c. voltage peak is not necessary for the test at

the lower voltage limit.
A.2 Test procedure – Mechanical puncture of the element

Mechanical puncture of the element is made by a nail, which is forced into the element

through an opening in the container. The test voltage may be d.c. or a.c., the choice being left

to the manufacturer.

If an a.c. voltage is used (at the high disconnection voltage u2), capacitor current shall be

recorded during the test and the timing of the puncture shall be made, to ascertain that the

breakdown is triggered to take place at the instant of the peak of the a.c. test voltage, or very

close to it.
NOTE 1 Puncture of only one element cannot be guaranteed.

NOTE 2 In order to limit the possibility of a flashover to the container along the nail, or through the hole caused

by the nail, the punctures will be performed in the elements connected, permanently or during the test, to the

container.

NOTE 3 DC voltage is especially suitable for capacitors having all elements in parallel.

---------------------- Page: 11 ----------------------
– 10 – IEC 60143-3:2015 © IEC 2015
Annex B
(informative)
Guide for coordination of fuse protection
B.1 General

The fuse is connected in series with the element that the fuse is designed to isolate if the

element becomes faulty. After the breakdown of an element, the fuse connected to it will blow,

and isolate it from the remaining part of the capacitor, which allows the unit to continue in

service.

The stresses on the fuse will depend on the rating of the capacitor unit, the number of parallel

connected units, connections (if any) between parallel units, etc.

The blowing of one or more fuses will cause changes of the voltage distribution and the

current distribution within the bank.

The voltage across sound unit(s) should not exceed the value given in IEC 60143-1.

Depending on the internal connection of the units, the blowing of one or more fuses may also

cause a change of voltage within the unit.

The remaining elements in a series group will have an increased working voltage, and the

manufacturer should, on request, give details of the voltage rise caused by blown fuses.

B.2 Protection sequence
The protection of a capacitor bank shall operate selectively.
The first step is the fusing of the element(s).

The second step is the relay protection of the bank (e.g. overcurrent or unbalance protection).

The third step is network or plant protection.
In large banks, an alarm stage may also be used.

NOTE 1 Depending on the output of the bank, the design of the relay protection etc., all the three steps are not

necessarily used in all capacitor banks.

NOTE 2 Unless the fuse always blows as a result of discharge energy within the voltage range given in

clause 2.2, the manufacturer will provide the current/time characteristic and tolerance of the fuse.

---------------------- Page: 12 ----------------------
IEC 60143-3:2015 © IEC 2015 – 11 –
Bibliography

IEC 60050-436:1990, International Electrotechnical Vocabulary – Chapter 436: Power

capacitors

IEC 60549:2013, High-voltage fuses for the external protection of shunt capacitors

IEC 60871-4:2014, Shunt capacitors for AC power systems having a rated voltage above

1 000 V – Part 4: Internal fuses

IEC 60931-3:1996, Shunt capacitors of the non-self-healing type for AC power systems

having a rated voltage up to and including 1000 V – Part 3: Internal fuses
___________
---------------------- Page: 13 ----------------------
– 12 – IEC 60143-3:2015 © IEC 2015
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