IEC TR 62271-306:2012/AMD1:2018

IEC TR 62271-306 ®
Edition 1.0 2018-08
TECHNICAL
REPORT
colour
inside
AMENDMENT 1
High-voltage switchgear and controlgear –
Part 306: Guide to IEC 62271-100, IEC 62271-1 and other IEC standards related to
alternating current circuit-breakers

IEC TR 62271-306:2012-12/AMD1:2018-08(en)

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IEC TR 62271-306 ®
Edition 1.0 2018-08
TECHNICAL
REPORT
colour
inside
AMENDMENT 1
High-voltage switchgear and controlgear –

Part 306: Guide to IEC 62271-100, IEC 62271-1 and other IEC standards related to

alternating current circuit-breakers

INTERNATIONAL
ELECTROTECHNICAL
COMMISSION
ICS 29.130.10 ISBN 978-2-8322-5911-5

– 2 – IEC TR 62271-306:2012/AMD1:2018
© IEC 2018
FOREWORD
This amendment has been prepared by subcommittee 17A: Switching devices, of IEC
technical committee 17: High-voltage switchgear and controlgear.
The text of this amendment is based on the following documents:
DTR Report on voting
17A/1161/DTR 17A/1169/RVDTR
Full information on the voting for the approval of this amendment can be found in the report
on voting indicated in the above table.
The committee has decided that the contents of this amendment and the base publication will
remain unchanged until the stability date indicated on the IEC web site 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• withdrawn,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.
A bilingual version of this publication may be issued at a later date.

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.
_____________
INTRODUCTION to the Amendment
At the SC 17A meeting held in Delft (NL) in 2013, the decision was made form a new
maintenance team (MT 57) with the task to amend/revise IEC 62271-306. The objective was
to update the publication to amendment 2 of IEC 62271-100. Together with MT 34
(IEC 62271-1), MT 36 (IEC 62271-100) and MT 28 (IEC 62271-101) the decision was made to
move some of the informative annexes to IEC 62271-306.
This amendment includes the following significant technical changes.
– Annex G of IEC 62271-1:2007 has been included;
– Annexes E, G, H, J, L and Q of IEC 62271-1:2007 have been included;
– I.2 of IEC 62271-100:2008 + A1:2012 has been included;
– Informative parts of Annex O of IEC 62271-100:2008 have been included;
– Former Clause 14 has been added to Clause 13;

© IEC 2018
– Clause 14 now has heading "Synthetic making and breaking tests". This clause contains
annexes A, B, C, D and G of IEC 62271-101;
– Clause 9 has been restructured;
– 16.4 (No-load transformer switching) has been rewritten;
– Annex B has been expanded to include information about fully compensated transmission
lines and cables;
– Annex D has been rewritten.
_____________
1.2 Normative references
Replace the existing references to IEC 62271-100, IEC 62271-101 and IEC 62271-110 by the
following new references:
IEC 62271-100:2008, High-voltage switchgear and controlgear – Part 100: Alternating current
circuit-breakers
Amendment 1:2012
Amendment 2:2017
IEC 62271-101:2012, High-voltage switchgear and controlgear – Part 101: Synthetic testing
IEC 62271-110:2012, High-voltage switchgear and controlgear – Part 110: Inductive load
switching
3.3 Capacitive current switching class C1 and C2
Replace the existing text of this subclause by the following new text:
Two classes are defined:
– Class C1: low probability of restrike;
– Class C2: very low probability of restrike.
IEC 60056 contained a definition of the term "restrike-free circuit-breaker". This definition was
removed when the capacitive current switching requirements and test procedures were
revised. The revised requirements and test procedures were first published in the first edition
of IEC 62271-100 (published in 2001). The reason why the term "restrike-free circuit-breaker"
was deleted from the standard was because it did not correspond to a physical reality.
The first edition of IEC 62271-100 introduced the term "restrike probability" during the type
tests, corresponding to a certain probability of restrike in service, which depends on several
parameters (see 9.4.6). For this reason, the term cannot be quantified in service.
The main differences in restrike performance between class C1 and C2 type tests are the
number of tests shots and the allowable number of restrikes. Class C2 tests are performed on
a pre-conditioned circuit-breaker. Pre-conditioning is done performing 3 breaking operations
at 60 % of the rated short-circuit current. The pre-conditioning was derived based on CIGRE
statistics and is considered to create interrupter wear that is broadly representative of long
term service conditions.
The choice for the user between class C1 and C2 depends on:
– the service conditions;
– 4 – IEC TR 62271-306:2012/AMD1:2018
© IEC 2018
– the operating frequency;
– the consequences of a restrike to the circuit-breaker or to the system.
Class C1 is acceptable for medium-voltage circuit-breakers and circuit-breakers applied for
infrequent switching of transmission lines and cables.
Class C2 is recommended for capacitor bank circuit-breakers and those used on frequently
switched transmission lines and cables.
The above given conditions are essential when choosing the circuit-breaker for a capacitive
switching application, the needed performance class and the voltage factor should be known
and demonstrated by the relevant type test. It is important to note that the performance class
may vary for different capacitive current switching applications. For example, a circuit-breaker
used to switch an overhead line may be tested for class C1 whereas the same circuit-breaker
is tested in accordance with class C2 for capacitor bank switching.
6.1.3.1 TRVs for terminal faults
Delete the penultimate paragraph of this subclause.
Add, at the end of the existing 6.3, the following new subclauses, figures and tables.
6.4 General considerations regarding TRV
6.4.1 General
The purpose of 6.4 is to provide a background framework for some of the TRV requirements.
6.4.2 TRV waveshapes
In some cases, particularly in systems with a voltage 100 kV and above, and where the short-
circuit currents are relatively large in relation to the maximum short-circuit current at the point
under consideration, the transient recovery voltage contains first a period of high rate of rise,
followed by a later period of lower rate of rise. This waveshape is generally adequately
represented by an envelope consisting of three line segments defined by means of four
parameters (see Figure 96).
The TRVs for terminal fault test-duties T100 and T60 represent cases where the major
contribution of fault current is over transmission lines from multiple sources. The TRVs consist
of the initial component at the fault bus and the additional component due to later arriving
multiple reflected waves at the fault bus. The TRVs are overdamped (exponential) owing to
the effect of the surge impedances of the lines and represented by four parameters to cover
both of the above components. For terminal fault test duties T30 and T10 TRV cases, the fault
current is from a single source and damping is determined by the involved circuit elements.
The TRVs are underdamped (oscillatory) and thus represented by two parameters.

© IEC 2018
IEC
Figure 96 – Representation of a four-parameter TRV and a delay line
In other cases, particularly in systems with a voltage less than 100 kV, or in systems with a
voltage greater than 100 kV in conditions where the short-circuit currents are relatively small
in relation to the maximum short-circuit currents limited by transformers, the transient
recovery voltage approximates to a damped single frequency oscillation. This waveshape is
adequately represented by an envelope consisting of two line segments defined by means of
two parameters (see Figure 97).

– 6 – IEC TR 62271-306:2012/AMD1:2018
© IEC 2018
IEC
Figure 97 – Representation of a specified TRV by a two-parameter
reference line and a delay line
Such a representation in terms of two parameters is a special case of representation in terms
of four parameters.
The influence of local capacitance on the source side of the circuit-breaker produces a slower
rate of rise of the voltage during the first few microseconds of the TRV. This is taken into
account by introducing a time delay.
6.4.3 Earthing of the system
The system may be earthed in different ways depending on system voltage and application.
The following definitions are used (Clause 3 of IEC 62271-100:2008 and as noted below):
solidly earthed (neutral) system (3.1.106 of IEC 62271-100:2008)
a system whose neutral point(s) is (are) directly earthed
[SOURCE: IEC 60050-601:1985, 601-02-25]
effectively earthed neutral system (3.1.128 of IEC 62271-100:2008)
system earthed through a sufficiently low impedance such that for all system conditions the
ratio of the zero-sequence reactance to the positive-sequence reactance (X /X ) is positive
0 1
and less than three, and the ratio of the zero-sequence resistance to the positive-sequence
reactance (R /X ) is positive and less than one. Normally such systems are solidly earthed
0 1
(neutral) systems or low impedance earthed (neutral) systems.
Note 1 to entry: For the correct assessment of the earthing conditions not only the physical earthing conditions
around the relevant location but the total system is to be considered.

© IEC 2018
non-effectively earthed neutral system (3.1.129 of IEC 62271-100:2008)
system other than effectively earthed neutral system, not meeting the conditions given in
3.1.128 of IEC 62271-100:2008. Normally such systems are isolated neutral systems, high
impedance earthed (neutral) systems or resonant earthed (neutral) systems
Note 1 to entry: For the correct assessment of the earthing conditions not only the physical earthing conditions
around the relevant location but the total system is to be considered.
6.4.4 Power frequency recovery voltage and first-pole-to-clear factor
6.4.4.1 General
The first-pole-to-clear factor (k ) is a function of the earthing arrangements of the system. As
pp
defined in 3.7.152 of IEC 62271-100:2008, it is the ratio of the power frequency voltage
across the interrupting pole before current interruption in the other poles, to the power
frequency voltage occurring across the pole or poles after interruption in all three poles. For
non-effectively earthed neutral systems, this ratio is or tends towards 1,5. For rated voltages
less than 170 kV, such systems are quite common, particular within Europe and Japan.
For effectively earthed neutral systems, the realistic and practical value is dependent upon
the sequence impedances of the actual earth paths from the location of the fault to the
various system neutral points (the ratio X /X ). The value used in IEC 62271-100 is taken to
0 1
be ≤ 3 (see Equation (144)). The X /X value is a standard value confirmed by system studies
0 1
of various networks. Hence, for rating purposes, IEC 62271-100 considers two valu
...