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• withdrawn,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 values for the
three-phase short-circuit condition. These are adequate for the many, different, system
earthing arrangements:
a) the non-effectively earthed, to cover all unearthed systems and those with some deliberate
additional impedance in the neutral system. A standardised value for k of 1,5 is used for
pp
all such systems;
b) all effectively earthed systems where it is accepted that some impedance exists. For
standardization purposes for power systems operating at 800 kV and below the value for
k used is 1,3. For ultra-high-voltage (UHV) power systems operating above 800 kV, k
pp pp
is 1,2 based on an X /X ratio of 2.
0 1
For single-phase-to-earth faults in solidly or effectively earthed neutral systems, the pole
factor k is 1,0.
pp
At transmission voltages, there has been an increase in interconnection and transformation,
particularly in major urban systems. The high number of transformer neutrals connected
effectively to earth causes the value of 1,3 to be questioned. Although this has been
considered, the text of IEC 62271-100 does not take these developments into account. It is
important for users with such systems to note that as k decreases towards unity the value of
pp
the second-pole-to-clear factor will fall. In addition, the value of the phase currents will
change. The three phases become three independent single-phases each with k
pp
approaching 1,0. In general the users of such systems are aware of this possibility and of the
need to consider the actual system conditions when assessing the suitability of their specified
requirements and the test evidence they are offered against these.
For rated voltages higher than 800 kV, systems are characterized by long transmission lines
and large transformers that contribute a relatively large part of the total short-circuit current.
The first-pole-to-clear factor is function of the X /X ratio that is in this case equal to or lower
0 1
than 2,0, as a consequence k is equal to or less than 1,2 and has been standardized to 1,2.
pp
Where the ratio of three-phase to single-phase earth fault current is 1,0, k is also 1,0.
pp
However, although this is normally assumed to be adequately covered by the use of the
three-phase requirements and the associated k of 1,2 or 1,3, it is important that evidence is
pp
provided to demonstrate the extended arc condition of the single-phase fault. In accordance
with IEC 62271-100, a full extinguishing window shall be demonstrated.

– 8 – IEC TR 62271-306:2012/AMD1:2018
© IEC 2018
It should be noted that in accordance with 6.108 of IEC 62271-100:2008, specific recovery
voltage conditions are required to demonstrate the ability of a circuit-breaker to clear double
earth faults.
Regarding earthing of the test circuit, reference is made to 6.103.3 of IEC 62271-100:2008.
6.4.4.2 Equations for the first, second and third-pole-to-clear factors
The equation for the first-pole-to-clear factor is:
3X
k = (144)
pp
XX+ 2
where X is the zero sequence, and X the positive sequence reactance of the system.
0 1
Table 39 gives the k values for various earthing arrangements based on the definitions
pp
given in 6.4.1.
Table 39 – First-pole-to-clear factors k
pp
Earthing arrangement X /X k System voltage
0 1 pp
Solidly earthed 1 1 All
Effectively earthed 2 1,2 > 800 kV
Effectively earthed 3 1,3 ≤ 800 kV
Non-effectively earthed 1,5
∞ ≤ 170 kV
NOTE Calculation of k for the effectively earthed case (X /X = 3) gives k = 1,286 which is then rounded to
pp 0 1 pp
1,3.
Following interruption of the first pole, the remaining two phases continue to conduct fault
current.
In systems with non-effectively earthed neutrals the second and third poles interrupt in series
under the phase-to-phase voltage so that for the second and third pole,
k = ,
p
where k is the pole-to-clear factor of the individual poles.
p
In systems with effectively earthed neutrals the second pole clears with a pole-to-clear factor
of,
3(X + XX + X )
0 01 1
k = (145)
p
XX+ 2
NOTE In Equations (144) and (145) the resistances are neglected.
Equation (145) can be expressed as a function of the ratio α = X /X :
0 1
31αα++
k =
p
2 + α
© IEC 2018
For the third-pole-to-clear in an effectively earthed system k = 1. Table 40 gives k for each
p p
clearing pole as a function of X /X as appropriate.
0 1
Table 40 – Pole-to-clear factors for each clearing pole
X /X Pole-to-clear factor
0 1
Ratio First Second Third
1 1,0 1,00 1,0
2 1,2 1,15 1,0
3 1,3 1,26* 1,0
∞ 1,5 0,866 0,866
* Equation (145) assumes that system impedances are inductances only.

The respective multiplying factors for the peak value of the TRV (u ) are given in Table 6 of
c
IEC 62271-100:2008. It is important to note that the amplitude factor is the same for each
pole. The multiplying factors are as applied to the power frequency voltages.
6.4.4.3 Standardised values for the second- and third- pole-to-clear factors
As discussed above, IEC 62271-100 has standardised values for the second and third-pole to
clear factors for three-phase testing. Subclause 13.3 deals with this topic in relation to
demonstration of arcing times for these poles and the appropriate pole factors relevant to
each opening pole. It is important to note that on systems where the neutral earthing is solid,
both the first-pole-to-clear factor of 1,3 and the values provided above for second
pole-to-clear factors are lower. This is likely to be a rare occurrence, generally associated
with urban systems where there are numerous effectively earthed transformers in close
proximity. Where such differences are significant, the user is generally aware that it may be
necessary to specify system-specific requirements and tests (e.g. extinguishing window and
single-phase short-circuit current).
Circuit-breakers are rated on the basis of their ability to interrupt a three-phase to earth fault
in either an effectively or non-effectively earthed neutral systems. Taking the former case, the
three poles clear in sequence:
• The first pole clears with k given by Equation (144) leaving a two-phase to earth fault.
pp
• The second pole clears with k given by Equation (145) leaving a single-phase to earth
p
fault. For the case of a two-phase to earth, the k for the first clearing pole is also given
pp
by Equation (145).
= 1 which is also applicable to the single-phase to earth fault case.
• Third pole with k
p
Similar logic can be applied to faults in non-effectively earthed neutral systems. A summary of
the pole-to-clear factors for the different fault cases is given in Table 41.

– 10 – IEC TR 62271-306:2012/AMD1:2018
© IEC 2018
Table 41 – Pole-to-clear factors for other types of faults
in non-effectively earthed neutral systems
Type of fault First-pole-to-clear Second-pole-to-clear Third-pole-to-clear
Phase-to-earth 1 - -
Two-phase not involving Simultaneous clearing of Simultaneous clearing of
earth
3 3
-
both poles: k = both poles: k =
p p
2 2
Two-phase-to-earth
31αα++
1 -
k =
p
2 + α
Three-phase not involving Simultaneous clearing of Simultaneous clearing of
earth
1,5 3 3
both poles: k = both poles: k =
p p
2 2
6.4.5 TRV characteristics
6.4.5.1 Terminal fault TRVs for rated voltages higher than 1 kV and less than 100 kV
6.4.5.1.1 General
Following the decision taken at the SC17A meeting in Beijing (CN) in October, 2002,
IEC SC 17A/WG35 has prepared a proposal for the revision of TRVs for circuit-breakers rated
above 1 kV and less than 100 kV.
This proposal used the input coming from former Working groups of CIGRE Study Committee
A3 (Switching Equipment) that have studied the necessity to adapt the TRV requirements for
circuit-breakers rated less than 100 kV. In 1983, a CIGRE SC A3 Task Force reported on
Transient Recovery Voltages in Medium Voltage Networks. The results of the study have been
published in Electra 88. Another CIGRE working group, WG 13.05, studied the TRVs
generated by clearing transformer fed faults and transformer secondary faults. The results
have been presented in Electra 102 (1985). In 1992, together with CIRED, CIGRE SC A3
created working group CC-03 to investigate again the definition of TRVs for medium voltage
switchgear. The outcome of these investigations has been published in CIGRE Technical
Brochure 134 (1998) and is in line with earlier studies.
The first edition of IEC 62271-100 (IEC 62271-100:2001) was amended in 2006 (Amendment
2) to include the new TRV values. The modifications can be summarized as follows:
a) In order to cover applications in all types of networks (distribution, industrial and
sub-transmission) for rated voltages higher than 1 kV and less than 100 kV, and for
standardization purposes, two types of systems and two classes of circuit-breakers are
defined:
– cable systems:
cable-systems are defined in 3.1.132 of IEC 62271-100:2008;
– line systems:
line systems are defined in 3.1.133 of IEC 62271-100:2008;
– Circuit-breaker class S1: circuit-breaker to be used in a cable system;
– Circuit-breaker class S2: circuit-breaker to be used in a line system.
b) A particular test duty T30 is specified for the special case of circuit-breakers intended to
be connected to a transformer with a connection of small capacitance (cable length less
than 20 m), in order to verify their capability to interrupt transformer-limited faults. This is
covered in Annex M of IEC 62271-100:2008.

© IEC 2018
In the general case where the capacitance of the connection is high enough, the normal
test duty T30 demonstrates the capability to interrupt transformer-limited faults.
6.4.5.1.2 Terminal fault TRV for circuit-breakers in line systems
6.4.5.1.2.1 General
In North America, line systems are prevalent at 72,5 kV and below. Therefore, the TRV
ratings as listed in Table 2 of ANSI C37.06-2000 were the basis to define the new Table 25 of
IEC 62271-100:2008. The values for t are 0,88 times the T values specified in ANSI.
3 2
NOTE 1 The factor 0,88 is derived from a pure "1-cos"-waveshape multiplied with ½ amplitude factor. The
standard TRV wave-shape "1-cos" in ANSI C37-06-2000 for rated voltages less than 100 kV did not coincide with
the precise mathematical equation for parallel or series damped circuits, for which another ratio t /T is applicable.
3 2
NOTE 2 TRV parameters are defined in the standard for rated voltages of 15 kV to 72,5 kV, for rated voltages
less than 15 kV the TRV parameters can be derived using k = 1,5, the values of amplitude factor, time t and time
pp 3
delay given in 6.4.1.2.2.2, 6.4.1.2.2.3 and 6.4.1.2.2.4.
6.4.5.1.2.2 Amplitude factor
For T100, T60, T30 and T10 the following values were taken from ANSI C37.06-2000:
– 1,54 for T100;
– 1,65 for T60;
– 1,74 for T30;
– 1,8 for T10.
6.4.5.1.2.3 Time t
The rate-of-rise of recovery voltage (RRRV) is calculated using Equation (146),
0,305
RRRV = 0,4U (146)
r
0,7
Time t for terminal fault is equal to 4,65 ×U , with t in µs and U in kV. Equation (146) was
3 r 3 r
derived from the values given in Table 2 of ANSI C37.06-2000 for rated voltages 15,5 kV,
25,8 kV, 48,3 kV and 72,5 kV. The same equation is used for other rated voltages.
6.4.5.1.2.4 Time delay
The time delay in Table 25 of IEC 62271-100:2008 is derived using the following equation,
t = 0,05 × t , as in the first edition of IEC 62271-100:2001 for rated voltages 48,3 kV – 52 kV
d 3
and 72,5 kV. The equation has been extended to the lower rated voltages as no change in the
initial part of the TRV wave-shape is expected (the initial part is exponential, even with the
short line lengths that can be met in distribution and sub-transmission systems). This
requirement is not judged excessive, as in the worst case (U = 15 kV), the time delay value of
r
2 µs is as specified for circuit-breakers with rated voltages higher than 72,5 kV.
It recognizes the fact that this time delay can be critical during short-line fault testing and test
duty T100 with ITRV and has therefore to be taken into account. However, as shown in Tables
13 and 14 of the first edition of IEC 62271-100 published in 2001, such verification can be
made when performing short-line fault tests. Therefore, as it is already the case for rated
voltages higher than 38 kV, it is allowed to have a longer time delay during testing of T100, up
, provided that short-line fault tests are performed. This possibility is indicated in
to 0,15 × t
Table 25 of IEC 62271-100:2008.

– 12 – IEC TR 62271-306:2012/AMD1:2018
© IEC 2018
6.4.5.1.3 Terminal fault TRV for circuit-breakers in cable systems
6.4.5.1.3.1 Amplitude factor
For T60, the value of 1,5 in the first edition of IEC 62271-100:2001 is kept, due to the positive
experience obtained.
For T30 and T10, the amplitude factor has been raised from 1,5 to respectively 1,6 and 1,7,
as the contribution to TRV comes mainly from the voltage variation across transformer(s),
which has low damping; this combined with source voltage results in a TRV with a relatively
high amplitude factor.
For T100, the value of 1,4 in the first edition of IEC 62271-100 published in 2001 is retained
owing to the positive experience with past editions of this standard.
6.4.5.1.3.2 Time delay
is as given in the first edition of IEC 62271-100 published in 2001 for rated
The time delay t
d
voltages less than 52 kV, t = 0,15 × t . The equation is generalized to all cable systems
d 3
(rated voltage less than 100 kV).
6.4.5.1.4 Terminal fault TRV for rated voltages equal to or higher than 100 kV
6.4.5.1.4.1 Amplitude factor
The values of the amplitude factors are given in IEC 62271-100. These values were adopted
into IEC 62271-100 as a result of system studies and generally remain acceptable.
6.4.5.1.4.2 Rate-of-rise of recovery voltage and time delay
The values for the rate-of-rise-of-recovery-voltage (RRRV) for the first-pole-to-clear, and the
associated time delay values, were derived from system studies, supported by system tests
performed in and before the mid-1970s. The values adopted (2 kV/μs etc.) have been shown
by this work to be adequate for all developed systems, and are generally acceptable for
others. IEC 62271-100 gives multipliers for the RRRV for the second and third poles-to-clear.
These values were derived by calculation.
6.4.5.1.5 Basis for the current TRV values of test-duty T10
Test-duty T10 is detailed in IEC 62271-100 and represents the following cases:
– a transformer limited fault condition with the circuit-breaker under consideration clearing a
fault on the remote side of the transformer.
In such circumstances, the fault current is limited by the impedance of the transformer to a
value, chosen for standardization purposes, of approximately 10 %. The value of 10 % is
historic, having been established from system studies and modelling using the typical
impedance values of transformers of standardised ratings.
For this duty, the fault-current is limited by the value of the impedance of the transformer.
The TRV is also dominated by the transformer characteristics which give it a (1-cos) wave-
shape form. The values given in IEC 62271-100 for amplitude factor, time coordinates and
delay line have been established from system studies and modelling during the 1960s and
before. The present values are accepted as being adequate for the vast majority of
systems;
– a long line fault for circuit-breakers having a rated voltage of 245 kV and above
For rated voltages below 245 kV, k = 1,5 in view of the fact that the contribution of
pp
transformers to the short-circuit current is relatively larger at smaller values of the short-
circuit current. Additionally, a comparatively large number of transformers having an
unearthed neutral are in service in earthed neutral systems. As the damping of the TRV
oscillation on a high-voltage transformer is less than in a network, an amplitude factor of

© IEC 2018
1,7 has been standardised except for line systems, with a voltage reduction across the
transformer of 10 % for voltages of 100 kV and above.
u = k × k × U 2/3
Thus, the TRV peak u for test-duty T10 is with the following
c pp af r
c
parameters:
a) for rated voltages below 100 kV:
1) for circuit-breakers in cable systems
k = 1,5 and k = 1,7.
pp af
2) for circuit-breakers in line systems
k = 1,5 and k = 1,8.
pp af
b) for rated voltages of 100 kV up to and including 170 kV:
k = 1,5 and k = 0,9 × 1,7 = 1,53.
pp af
c) for rated voltages of 245 kV up to and including 800 kV:
k = 1,3 and k = 1,76.
pp af
d) for rated voltages above 800 kV:
k = 1,2 and k =1,76.
pp af
6.4.6 Short-line fault TRV
6.4.6.1 General
Short-line fault (SLF) is a mandatory duty for circuit-breakers with rated voltages 15 kV and
above that are directly connected to overhead lines. As specified already in
IEC 62271-100:2001 for circuit-breakers rated 48,3 kV and above, the rated short-circuit
current shall be higher than 12,5 kA (i.e. I ≥ 16 kA).
sc
As it is considered that there are only few line systems below 15 kV, no short-line fault
breaking capability is required for rated voltages below 15 kV. In the rare cases where a
circuit-breaker with a voltage rating below 15 kV is directly connected to an overhead line, no
short-line fault requirement is necessary as the line contribution to the TRV would be too low
to produce a significant stress.
NOTE For class S2 circuit-breakers, short-line fault test-duty L90 is not required as it would lead to an unrealistic
short length of faulted line.
The short-line fault test specified is regarded as covering three-phase short-line faults as well
as two-phase and single-phase faults for the following reasons:
– the representative surge impedance, seen from the terminals of the clearing pole, is such
that for all cases the RRRV for all three poles to clear is covered by the specified
characteristics listed in Table 8 of IEC 62271-100:2008;
– the single-phase short-line fault test, with an interrupting window of (180°−dα), covers the
requirement for the multi-phase fault cases for effectively-earthed and non-effectively
earthed systems;
– the withstand of the peak value of TRV during three-phase fault interruption is
demonstrated by terminal fault test duty T100.
6.4.6.2 Rated voltage less than 100 kV
6.4.6.2.1 General
In IEC 62271-100:2001, short-line fault requirements have been specified for circuit-breakers
with a rated voltage of 52 kV and 72,5 kV, in the range of rated voltages considered in this
edition, and directly connected to overhead-lines.

– 14 – IEC TR 62271-306:2012/AMD1:2018
© IEC 2018
In IEC 62271-100:2008, short-line fault requirements are specified for class S2 circuit-
breakers with a rated voltage of 15 kV and above and directly connected (with busbars) to
overhead-lines, irrespective of the type of network on the source side.
As the network and substation topology and layout for 48,3 kV is identical to those of 52 kV
and 72,5 kV systems, the short-line test duty for 48,3 kV is specified in a way similar to 52 kV
and 72,5 kV.
For rated voltages of 15 kV to 38 kV, the characteristics and procedure are slightly different.
As normally no equipment is connected to the line side of the circuit-breaker, the line
characteristics are adapted to virtually no delay capacitance: t < 0,1 μs. As the line length to
dL
the fault location should correspond to realistic distances, the test duty L has been dropped
and the tolerances on the line length for L have been adapted.
Time t and the amplitude factor of the supply circuit is the same as for terminal fault test-duty
T100.
6.4.6.2.2 Rated voltage equal to or higher than 100 kV
The amplitude factor and the inherent value of the RRRV of the supply circuit are as specified
for terminal fault test duty T100. During a SLF interruption the RRRV on the supply side is
equal to the inherent value of RRRV for the supply circuit multiplied by the ratio of the SLF
current divided by the rated short-circuit breaking current.
6.4.7 Out-of-phase TRV
Not enough system information is available to revise TRV parameters for breaking in the out-
of-phase condition. CIGRE SC A3 has been asked to investigate the system and service
conditions leading to out-of-phase current clearing. Therefore, the TRVs for out-of-phase
breaking are basically unchanged.
The values of t for out-of-phase are in all cases two times the value for terminal fault T100.
6.4.8 TRV for series reactor fault
Due to the very small inherent capacitance of a number of current-limiting reactors, the
natural frequency of transients involving these reactors can be very high. A circuit-breaker
installed immediately in series with such type of reactor will face a high-frequency TRV when
clearing a terminal fault (reactor at supply side of circuit-breaker) or clearing a fault behind
the reactor (reactor at load side of circuit-breaker). The resulting TRV frequency generally
exceeds by far the standardized TRV values.
In these cases, it is necessary to take mitigation measures, such as the application of
capacitors in parallel to the reactors or connected to earth. The available mitigation measures
are very effective and cost efficient [125]. It is strongly recommended to use them, unless it
can be demonstrated by tests that a circuit-breaker can successfully clear faults with the
required high-frequency TRV.
Considering the economical aspect as well as service experience with TRV mitigation
measures, there is no need for special requirements in IEC 62271-100 for circuit-breakers for
this type of application.
More information is given in IEEE Std. C37.011 [126].
6.4.9 TRV for last clearing poles / tests circuit topology
In Table 2 of IEC 62271-100:2001, multipliers for transient recovery voltage values for second
and third clearing poles are given for circuit-breakers with rated voltages higher than 72,5 kV.

© IEC 2018
Under NOTE 1, it is stated that for voltages equal to or lower than 72,5 kV, the values are
under consideration.
For circuit-breakers with rated voltages equal to or lower than 72,5 kV, as not enough
information is available to define values other than those specified for higher rated voltages,
IEC SC17A has decided during its meeting in Montreal (CA), October 2003, to extend the
validity of Table 2 to all rated voltages higher than 1 kV.
6.5 Calculation of TRVs
6.5.1 General
TRV parameters are defined as a function of the rated voltage (U), the rated
r
) and the amplitude factor (k ). k is a function of the earthing of
first-pole-to-clear factor (k
pp af pp
the system neutral. The rated values of k are:
pp
– 1,2 for terminal fault breaking by circuit-breakers with rated voltages higher than 800 kV in
effectively earthed neutral systems;
– 1,3 for terminal fault breaking by circuit-breakers for rated voltages up to and including
800 kV in effectively earthed neutral systems;
– 1,5 for terminal fault breaking by circuit-breakers for rated voltages less than 245 kV in
non-effectively earthed neutral systems.
6.5.2 Rated voltages less than 100 kV
A representation by two parameters of the prospective TRV is used for all test-duties.
– For circuit-breakers in cable systems.
2/3
The TRV peak value u = k ×k ×U where k is equal to 1,4 for test-duty T100, 1,5
c pp af r af
for test-duty T60, 1,6 for test duty T30 and 1,7 for test duty T10, 1,25 for out-of-phase
breaking.
Time t for test-duty T100 is taken from Tables 24 and 43 of IEC 62271-100:2008 with
IEC 62271-100:2008/AMD1:2012 and IEC 62271-100:2008/AMD2:2017. Time t for test-
duties T60, T30 and T10 is obtained by multiplying the time t for test-duty T100 by 0,44
(for T60), 0,22 (for T30) and 0,22 (for T10).
– For circuit-breakers in line systems.
2/3
TRV peak value u = k ×k ×U where k is equal to 1,54 for test-duty T100 and the
c pp af r af
supply side circuit for short-line fault, 1,65 for test-duty T60, 1,74 for test duty T30 and 1,8
for test duty T10, 1,25 for out-of-phase breaking.
Time t for test-duty T100 is taken from Tables 25 and 44 of IEC 62271-100:2008 with
IEC 62271-100:2008/AMD1:2012 and IEC 62271-100:2008/AMD2:2017. Time t for test-
duties T60, T30 and T10 is obtained by multiplying the time t for test-duty T100 by 0,67
(for T60), 0,40 (for T30) and 0,40 (for T10).
– Time delay t for test-duty T100 is 0,15t for cable systems, 0,05t for line systems, 0,05t
d 3 3 3
for the supply side circuit for short-line fault.
– Time delay t is 0,15t for test-duties T60, T30 and T10 and for out-of-phase breaking.
d 3
– Voltage u'=u /3.
c
– Time t' is derived from u', t and t according to Figure 97, t' = t + t /3.
3 d d 3
– 16 – IEC TR 62271-306:2012/AMD1:2018
© IEC 2018
6.5.3 Rated voltages from 100 kV to 800 kV
A representation by four parameters of the prospective TRV is used for test-duties T100 and
T60, and the supply circuit of SLF for test duties L and L and for out-of-phase test duties
90 75
OP1 and OP2 and by two parameters for test-duties T30 and T10.
– First reference voltage u 0,75× kU×× 2 / 3
1 pp r
– Time t for terminal fault test duties is derived from u and the specified value of the rate
1 1
of rise u /t . For test duties OP1 and OP2, t is two times t for test duty T100 and the rate
1 1 1 1
of rise is derived from u and t .
1 1
– TRV peak value
u= k × k××U 2/ 3
c pp af r
where k is equal to 1,4 for test-duty T100 and for the supply side circuit for SLF, 1,5 for
af
test-duty T60, 1,54 for test-duty T30, 0,9 × 1,7 for test-duty T10, and 1,25 for out-of-phase
breaking.
– Time t is equal to 4t for test-duty T100 and for the supply side circuit for short-line fault
2 1
and between t (for T100) and 2t (for T100) for out-of-phase breaking. Time t is equal to
2 2 2
6t for T60.
– For test-duties T30 and T10, time t is derived from u and the specified value of the rate
3 c
of Figure 96. Time delay t is 2 µs for test-duty T100, between 2 µs and 0,3t for test-duty
d 1
T60, between 2 µs and 0,1t for test duties OP1 and OP2. Time delay is 0,15 t for test-
1 3
duties T30 and T10. For the supply side circuit for short-line fault the time delay is equal to
2 µs. When short-line fault tests are performed, the time delay t for test-duty T100 can be
d
extended up to 0,28 t . The relevant value of t to be used for testing is given in 6.104.5.2
1 d
to 6.104.5.5 of IEC 62271-100:2008.
– Voltage u' = u /2 for test-duties T100 and T60 and the supply side for SLF and out-of-
phase breaking, and u /3 for test-duties T30 and T10.
c
– Time t' is derived from u', u /t and t for test-duties T100, T60 and the supply circuit for
1 1 d
SLF and out-of-phase breaking, and in accordance with Figure 96; and from u', u /t and t
c 3 d
for test-duties T30 and T10 in accordance with Figure 97.
6.5.4 Rated voltages higher than 800 kV
A representation by four parameters of the prospective TRV is used for test-duties T100 and
T60, and the supply circuit of SLF for test duties L and L and by two parameters for test-
90 75
duties T30, T10 and for out-of-phase test duties OP1 and OP2.
– First reference voltage u 0,75× kU×× 2 / 3
1 pp r
– Time t for terminal fault test duties is derived from u and the specified value of the rate
1 1
of rise u /t .
1 1
– Time t for out-of-phase test duties OP1 and OP2 is derived from u and the specified
3 c
value of the rate of rise.
– TRV peak value u= k × k××U 2/ 3
c pp af r
is equal to 1,5 for test-duty T100 and for the supply side circuit for SLF, 1,5 for
where k
af
test-duty T60, 1,54 for test-duty T30, 1,76 for test-duty T10, and 1,25 for out-of-phase
breaking.
– Time t is equal to 3 t for test-duty T100 and for the supply side circuit for short-line fault.
Time t is equal to 4,5 t for T60.
– For test-duties T30 and T10, time t is derived from u and the specified value of the rate
3 c
of rise u /t .
c 3
– Time delay t is 2 µs for test-duty T100, between 2 µs and 0,3 t for test-duty T60. Time
d 1
delay is 0,15 t for test duties T30 and T10, 0,05 t for test duties OP1 and OP2. For the
3 3
supply side circuit for short-line fault the time delay is equal to 2 µs. When short-line fault
=
=
© IEC 2018
tests are performed, the time delay t for test-duty T100 can be extended up to 0,28 t .
d 1
The relevant value of t to be used for testing is given in 6.104.5.2 to 6.104.5.5.
d
– Voltage u' = u /2 for test-duties T100 and T60 and the supply side for SLF, and u /3 for
1 c
test-duties T30, T10 and out-of-phase test duties.
– Time t' is derived from u', u /t and t for test-duties T100, T60 and the supply circuit for
1 1 d
SLF, and in accordance with Figure 96; and from u', u /t and t for test-duties T30, T10
c 3 d
and out-of-phase test duties in accordance with Figure 97.
7.1.2 Technical comment
Replace the last paragraph of this subclause by the following:
As stated in 7.1.1, short-line faults tests apply to circuit-breakers directly connected to
overhead lines. Direct connection is defined as a connection between the circuit-breaker and
overhead line having a capacitance less tha
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