IEC 62271-101:2006

IEC 62271-101 ®
Edition 1.1 2010-11
INTERNATIONAL
STANDARD
NORME
INTERNATIONALE
colour
inside
High-voltage switchgear and controlgear –
Part 101: Synthetic testing
Appareillage à haute tension –
Partie 101: Essais synthétiques

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IEC 62271-101 ®
Edition 1.1 2010-11
INTERNATIONAL
STANDARD
NORME
INTERNATIONALE
colour
inside
High-voltage switchgear and controlgear –
Part 101: Synthetic testing
Appareillage à haute tension –
Partie 101: Essais synthétiques

INTERNATIONAL
ELECTROTECHNICAL
COMMISSION
COMMISSION
ELECTROTECHNIQUE
INTERNATIONALE
PRICE CODE
C7
CODE PRIX
ICS 29.130.10
ISBN 978-2-88912-191-5
– 2 – 62271-101  IEC:2006+A1:2010

CONTENTS
FOREWORD . 6

INTRODUCTION (to amendment 1) . 8

1 Scope . 9

2 Normative references . 9

3 Terms and definitions . 9

4 Synthetic testing techniques and methods for short-circuit breaking tests . 11

4.1 Basic principles and general requirements for synthetic breaking test

methods . 11
4.2 Synthetic test circuits and related specific requirements for breaking tests . 14
4.3 Three-phase synthetic test methods . 17
5 Synthetic testing techniques and methods for short-circuit making tests . 19
5.1 Basic principles and general requirements for synthetic making test methods . 19
5.2 Synthetic test circuit and related specific requirements for making tests . 20
6 Specific requirements for synthetic tests for making and breaking performance
related to the requirements of 6.102 through 6.111 of IEC 62271-100 . 21

Annex A (informative) Current distortion . 42
Annex B (informative) Current injection methods. 58
Annex C (informative) Voltage injection methods . 63
Annex D (informative) Duplicate circuit (transformer or Skeats circuit) . 66
Annex E (normative) Information to be given and results to be recorded for synthetic tests . 69
Annex F (informative) Special procedures for testing circuit-breakers having parallel
breaking resistors . 70
Annex G (informative) Synthetic methods for capacitive-current switching . 73
Annex H (informative) Re-ignition methods to prolong arcing . 85
Annex I (normative) Reduction in di/dt and TRV for test duty T100a . 89
Annex J (informative) Three-phase synthetic test circuits . 103
Annex K (normative) Test procedure using a three-phase current circuit and one
voltage circuit . 111
Annex L (normative) Splitting of test duties in test series taking into account the
associated TRV for each pole-to-clear . 130
Annex M (normative) Tolerances on test quantities for type tests . 140

Annex N (informative) Typical test circuits for metal-enclosed and dead tank circuit
breakers . 143

Bibliography . 143

Figure 1 – Interrupting process – Basic time intervals . 33
Figure 2 – Example of recovery voltage . 34
Figure 3 – Equivalent surge impedance of the voltage circuit for the current injection
method . 35
Figure 4 – Making process – Basic time intervals . 36
Figure 5 – Typical synthetic make circuit for single-phase tests . 38
Figure 6 – Typical synthetic make circuit for three-phase tests (k = 1,5) . 39
pp
Figure 7 – Comparison of arcing time settings during three-phase direct tests (left)
and three-phase synthetic (right) for T100s with k = 1,5 . 40
pp
62271-101  IEC:2006+A1:2010 – 3 –

Figure 8 – Comparison of arcing time settings during three-phase direct tests (left)

and three-phase synthetic (right) for T100a with k = 1,5 . 41
pp
Figure A.1 – Direct circuit, simplified diagram . 49

Figure A.2 – Prospective short-circuit current . 49

Figure A.3 – Distortion current . 49

Figure A.4 – Distortion current . 50

Figure A.5 – Simplified circuit diagram . 51

Figure A.6 – Current and arc voltage characteristics for symmetrical current . 52

Figure A.7 – Current and arc voltage characteristics for asymmetrical current . 53

Figure A.8 – Reduction of amplitude and duration of final current loop of arcing . 54
Figure A.9 – Reduction of amplitude and duration of final current loop of arcing . 55
Figure A.10 – Reduction of amplitude and duration of final current loop of arcing . 56
Figure A.11 – Reduction of amplitude and duration of final current loop of arcing . 57
Figure B.1 – Typical current injection circuit with voltage circuit in parallel with the test
circuit-breaker . 60
Figure B.2 – Injection timing for current injection scheme with circuit B.1 . 60
Figure B.3 – Typical current injection circuit with voltage circuit in parallel with the
auxiliary circuit-breaker . 61
Figure B.4 – Injection timing for current injection scheme with circuit B.3 . 61
Figure B.5 – Examples of the determination of the interval of significant change of arc
voltage from the oscillograms . 62
Figure C.1 – Typical voltage injection circuit diagram with voltage circuit in parallel
with the auxiliary circuit-breaker (simplified diagram) . 64
Figure C.2 – TRV waveshapes in a voltage injection circuit with the voltage circuit in
parallel with the auxiliary circuit-breaker . 65
Figure D.1 – Transformer or Skeats circuit . 67
Figure D.2 – Triggered transformer or Skeats circuit . 68
Figure G.1 – Capacitive current circuits (parallel mode) . 76
Figure G.2 – Current injection circuit . 77
Figure G.3 – LC oscillating circuit . 78
Figure G.4 – Inductive current circuit in parallel with LC oscillating circuit . 79
Figure G.5 – Current injection circuit, normal recovery voltage applied to both
terminals of the circuit-breaker . 80
Figure G.6 – Synthetic test circuit (series circuit), normal recovery voltage applied to
both sides of the test circuit breaker . 81

Figure G.7 – Current injection circuit, recovery voltage applied to both sides of the
circuit-breaker . 82
Figure G.8 – Making test circuit . 83
Figure G.9 – Inrush making current test circuit . 84
Figure H.1 – Typical re-ignition circuit diagram for prolonging arc-duration . 86
Figure H.2 – Combined Skeats and current injection circuits . 87
Figure H.3 – Typical waveforms obtained during an asymmetrical test using the circuit
in Figure H.2 . 88
Figure J.1a – Three-phase synthetic combined circuit . 105
Figure J.1b – Waveshapes of currents, phase-to-ground and phase-to phase voltages
during a three-phase synthetic test (T100s; k = 1,5 ) performed according to the
pp
three-phase synthetic combined circuit . 106
Figure J.2a – Three-phase synthetic circuit with injection in all phases for k = 1,5 . 107
pp
– 4 – 62271-101  IEC:2006+A1:2010

Figure J.2b – Waveshapes of currents and phase-to-ground voltages during a three-

phase synthetic test (T100s; k =1,5) performed according to the three-phase
pp
synthetic circuit with injection in all phases . 108

Figure J.3a – Three-phase synthetic circuit for terminal fault tests with k = 1,3
pp
(current injection method) . 109

Figure J.3b – Waveshapes of currents, phase-to-ground and phase-to-phase voltages

during a three-phase synthetic test (T100s; k =1,3 ) performed according to the
pp
three-phase synthetic circuit shown in Figure J.3a . 109

Figure J.3c – TRV voltages waveshapes of the test circuit described in Figure J.3a . 110

Figure K.1 – Example of a three-phase current circuit with single-phase synthetic injection . 121

Figure K.2 – Representation of the testing conditions of Table K.1a . 122
Figure K.3 – Representation of the testing conditions of Table K.1b . 123
Figure K.4 – Representation of the testing conditions of Table K.2a . 124
Figure K.5 – Representation of the testing conditions of Table K.2b . 125
Figure K.6 – Representation of the testing conditions of Table K.3a . 126
Figure K.7 – Representation of the testing conditions of Table K.3b . 127
Figure K.8 – Representation of the testing conditions of Table K.4a . 128
Figure K.9 – Representation of the testing conditions of Table K.4b . 129
Figure L.1 – Graphical representation of the test shown in Table L.1 . 136
Figure L.2 – Graphical representation of the test shown in Table L.2 . 137
Figure N.1 – Test circuit for unit testing (circuit-breaker with interaction
due to gas circulation) . 144
Figure N.2 – Half-pole testing of a circuit-breaker in test circuit given by Figure N.1 –
Example of the required TRVs to be applied between the terminals of the unit(s)
under test and between the live parts and the insulated enclosure . 145
Figure N.3 – Synthetic test circuit for unit testing (if unit testing is allowed as per
Subclause 6.102.4.2 of IEC 62271-100:2008) . 146
Figure N.4 – Half-pole testing of a circuit-breaker in the test circuit of Figure N.3 –
Example of the required TRVs to be applied between the terminals of the unit(s)
under test and between the live parts and the insulated enclosure . 147
Figure N.5 – Capacitive current injection circuit with enclosure of the circuit-breaker
energized . 148
Figure N.6 – Capacitive synthetic circuit using two power-frequency sources
and with the enclosure of the circuit-breaker energized . 149
Figure N.7 – Capacitive synthetic current injection circuit – Example of unit testing
on half a pole of a circuit-breaker with two units per pole – Enclosure energized

with d.c. voltage source . 150
Figure N.8 – Symmetrical synthetic test circuit for out-of-phase switching tests on a
complete pole of a circuit-breaker . 151
Figure N.9 – Full pole test with voltage applied to both terminals
and the metal enclosure . 152

Table 1 – Test circuits for test duties T100s and T100a . 17
Table 2 – Test duties T10, T30, T60 and T100s . 18
Table 2a – First-pole-to-clear factor: 1,5 – Test parameters during three-phase
interruption . 18
Table 2b – First-pole-to-clear factor: 1,3 – Test parameters during three-phase
interruption . 18
Table 3 – Synthetic test methods for test duties T10, T30, T60, T100s, T100a, SP,
DEF, OP and SLF . 31

62271-101  IEC:2006+A1:2010 – 5 –

Table I.1a – Last current loop parameters for 50 Hz operation in relation to short-circuit

test duty T100a τ = 45 ms . 90

Table I.1b – Last current loop parameters for 50 Hz operation in relation to short-circuit

test duty T100a τ = 60 ms . 91

Table I.1c – Last current loop parameters for 50 Hz operation in relation to short-circuit
test duty T100a τ = 75 ms . 92

Table I.1d – Last current loop parameters for 50 Hz operation in relation to short-circuit

test duty T100a τ = 120 ms . 93

Table I.2a – Last current loop parameters for 60 Hz operation in relation to short-circuit

test duty T100a τ = 45 ms . 94

Table I.2b – Last current loop parameters for 60 Hz operation in relation to short-circuit
test duty T100a τ = 60 ms . 95
Table I.2c – Last current loop parameters for 60 Hz operation in relation to short-circuit
test duty T100a τ = 75 ms . 96
Table I.2d – Last current loop parameters for 60 Hz operation in relation to short-circuit
test duty T100a τ = 120 ms . 97
Table I.3a I.1a – Last loop di/dt reduction for 50 Hz under three-phase conditions with
the first pole to clear in phase A and the required asymmetry in phase C . 98
Table I.3b I.1b – Last loop di/dt reduction for 60 Hz under three- phase conditions with
the first pole to clear in phase A and the required asymmetry in phase C . 99
Table I.4a I.2a – Corrected TRV values for k = 1,3 and f = 50 Hz . 100
pp r
Table I.4b I.2b – Corrected TRV values for k = 1,3 and f = 60 Hz . 101
pp r
Table I.4c I.2c – Corrected TRV values for k = 1,5 and f = 50 Hz . 102
pp r
Table I.4d I.2d – Corrected TRV values for k = 1,5 and f = 60 Hz . 102
pp r
Table K.1a – Demonstration of arcing times for a first-pole-to-clear factor of 1,5 . 112
Table K.1b – Alternative demonstration of arcing times for a first-pole-to-clear factor
of 1,5 . 113
Table K.2a – Demonstration of arcing times for a first-pole-to-clear factor of 1,3 . 114
Table K.2b – Alternative demonstration of arcing times for a first-pole-to-clear factor
of 1,3 . 115
Table K.3a – Demonstration of arcing times for a first-pole-to-clear factor of 1,5 . 117
Table K.3b – Alternative demonstration of arcing times for a first-pole-to-clear factor
of 1,5 . 118
Table K.4a – Demonstration of arcing times for a first-pole-to-clear factor of 1,3 . 119
Table K.4b – Alternative demonstration of arcing times for a first-pole-to-clear factor
of 1,3 . 120

Table L.1 – Test procedure for a first-pole-to-clear factor of 1,5 . 131
Table L.2a – Alternative demonstration of arcing times for a first-pole-to-clear factor
of 1,3 . 132
Table L.2b – Simplified test procedure for a first-pole-to-clear factor of 1,3 . 133
Table L.3 – Test procedure for asymmetrical currents in the case of a first-pole-to-
clear factor of 1,5 . 134
Table L.4 – Test procedure for asymmetrical currents in the case of a first-pole-to-
clear factor of 1,3 . 135
Table L.5 – Required arcing windows in ° for different asymmetrical conditions, f = 50 Hz . 138
r
Table L.6 – Required arcing windows in ° for different asymmetrical conditions, f = 60 Hz . 139
r
Table M.1 – Tolerances on test quantities for type tests . 141

– 6 – 62271-101  IEC:2006+A1:2010

INTERNATIONAL ELECTROTECHNICAL COMMISSION

___________
HIGH-VOLTAGE SWITCHGEAR AND CONTROLGEAR –

Part 101: Synthetic testing
FOREWORD
1) The International Electrotechnical Commission (IEC) is a worldwide organization for standardization comprising
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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 IEC 62271-101 consists of the first edition (2006)
[documents 17A/753/FDIS and 17A/755/RVD] and its amendment 1 (2010) [documents
17A/907/FDIS and 17A/919/RVD]. It bears the edition number 1.1.
The technical content is therefore identical to the base edition and its amendment and
has been prepared for user convenience. A vertical line in the margin shows where the
base publication has been modified by amendment 1. Additions and deletions are
displayed in red, with deletions being struck through.

62271-101  IEC:2006+A1:2010 – 7 –

International Standard IEC 62271-101 has been prepared by subcommittee 17A: High-voltage
switchgear and controlgear, of IEC technical committee 17: Switchgear and controlgear.

This publication has been drafted in accordance with the ISO/IEC Directives, Part 2.

This publication shall be read in conjunction with IEC 62271-100. The numbering of the
subclauses of Clause 6 is the same as in IEC 62271-100. However, not all subclauses of IEC
62271-100 are addressed; merely those where synthetic testing has introduced changes.

The IEC 62271-100 series consists of the following parts, under the general title High-voltage
switchgear and controlgear:
Part 100: High-voltage alternating-current circuit-breakers
Part 101: Synthetic testing
Part 102: Alternating current disconnectors and earthing switches
Part 104: Alternating current switches for rated voltages of 52 kV and above
Part 105: Alternating current switch-fuse combinations
Part 107: Alternating current fused circuit-switchers for rated voltages above 1 kV up to and
including 52 kV
Part 108: High voltage alternating current disconnecting circuit-breakers for rated voltages
of 72,5 kV and above
Part 109: Alternating-current series capacitor by-pass switches
Part 110: Inductive load switching
A list of the other parts belonging to the IEC 62271 series can be found on the IEC website
http://www.iec.ch. Further information is available on http://tc17.iec.ch.
The committee has decided that the contents of the base publication and its amendments 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.
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 publication using a colour printer.

___________
Some of these parts are still in the process of being developed.

– 8 – 62271-101  IEC:2006+A1:2010

INTRODUCTION
(to amendment 1)
This amendment cancels and replaces IEC 61633.

The original edition of IEC 62271-101 (2006) makes extensive reference to
IEC 62271-100:2001. Since then, a new edition of IEC 62271-100 has been published (2008).

Within this amendment, references are made to IEC 62271-100:2008. Unless they are

explicitly mentioned in this amendment, all of the references in the original edition of

IEC 62271-101 (2006) still make reference to IEC 62271-100:2001. A second amendment to

IEC 62271-101, which will update all cross-references to the new IEC 62271-100:2008, is

under consideration.
62271-101  IEC:2006+A1:2010 – 9 –

HIGH-VOLTAGE SWITCHGEAR AND CONTROLGEAR –

Part 101: Synthetic testing
1 Scope
This part of IEC 62271 mainly applies to a.c. circuit-breakers within the scope of IEC 62271-100.

It provides the general rules for testing a.c. circuit-breakers, for making and breaking capacities
over the range of test duties described in 6.102 to 6.111 of IEC 62271-100, by synthetic methods.
NOTE Circuits for the test duties described in 6.111 have not yet been standardized. However, present methods
are given in Annex G.
It has been proven that synthetic testing is an economical and technically correct way to test
high-voltage a.c. circuit-breakers according to the requirements of IEC 62271-100 and that it
is equivalent to direct testing.
The methods and techniques described are those in general use. The purpose of this
standard is to establish criteria for synthetic testing and for the proper evaluation of results.
Such criteria will establish the validity of the test method without imposing restraints on
innovation of test circuitry.
2 Normative references
The following referenced documents are indispensable for the application of this document.
For dated references, only the edition cited applies. For undated references, the latest edition
of the referenced document (including any amendments) applies.
IEC 61633:1995, High-voltage alternating current circuit-breakers – Guide for short-circuit and
switching test procedures for metal-enclosed and dead tank circuit-breakers
IEC 62271-100:2001 2008, High-voltage switchgear and controlgear – Part 100: High-voltage
Alternating current circuit-breakers
IEC 62271-308:2002, High-voltage switchgear and controlgear – Part 308: Guide for asym-
metrical short-circuit test duty T100a

3 Terms and definitions
For the purposes of this document, the terms and definitions of IEC 62271-100, as well as the
following terms and definitions, apply.

3.1
direct test
test in which the applied voltage, the current and the transient and power-frequency recovery
voltages are all obtained from a circuit having a single-power source, which may be a power
system or special alternators as used in short-circuit testing stations or a combination of both
___________
Unless explicitly otherwise mentioned, all of the references to IEC 62271-100 make reference to IEC 62271-100:2001. A
second amendment to IEC 62271-101, which will update all cross-references to the new IEC 62271-100:2008, is under
consideration.
– 10 – 62271-101  IEC:2006+A1:2010

3.2
synthetic test
test in which all of the current, or a major portion of it, is obtained from one source (current

circuit), and in which the applied voltage and/or the recovery voltages (transient and power

frequency) are obtained wholly or in part from one or more separate sources (voltage circuits)

3.3
test circuit-breaker
circuit-breaker under test (see 6.102.2 of IEC 62271-100:2001)

3.4
auxiliary circuit-breaker(s)
circuit-breaker(s) forming part of a synthetic test circuit used to put the test circuit-breaker
into the required relation with various circuits
3.5
current circuit
that part of the synthetic test circuit from which all or the major part of the power-frequency
current is obtained
3.6
voltage circuit
that part of the synthetic test circuit from which all or the major part of the applied voltage
and/or recovery voltage is obtained
3.7
prospective current (of a circuit and with respect to a circuit-breaker)
current that would flow in the circuit if each pole of the test and auxiliary circuit-breakers were
replaced by a conductor of negligible impedance
[IEV 441-17-01, modified]
3.8
actual current
current through the test circuit-breaker (prospective current modified by the arc voltage of the
test and auxiliary circuit-breakers)
3.9
distortion current
calculated current equal to the difference between the prospective current and the actual
current
3.10
post-arc current
current which flows through the arc gap of a circuit-breaker when the current and arc voltage
have fallen to zero and the transient recovery voltage has begun to rise
3.11
current-injection method
synthetic test method in which the voltage circuit is applied to the test circuit-breaker before
power-frequency current zero
3.12
initial transient making current
ITMC
transient current which flows through the circuit-breaker at the moment of voltage breakdown
prior to the initiation of current from the current circuit during making

62271-101  IEC:2006+A1:2010 – 11 –

3.13
injected current
current supplied by the voltage circuit of a current injection circuit when it is connected to the

circuit-breaker under test
3.14
voltage-injection method
synthetic test method in which the voltage circuit is applied to the test circuit-breaker after

power frequency current zero
3.15
reference system conditions
conditions of an electrical system having the parameters from which the rated and test values
of IEC 62271-100 are derived
3.16
time delay of making device
t
m
time interval, during synthetic making test, between the instant of breakdown of the applied
voltage and the initiation of current from the current circuit
3.17
minimum clearing time
sum of the minimum opening time, minimum relay time (½ cycle), and the minimum arcing
time for the minor loop of the first-pole-to-clear, during test duty T100a only, as declared by
the manufacturer. This definition should be used only for the determination of the test
parameters for test duty T100a.
NOTE 1 The minimum clearing time obtained during the tests should not be lower than the value declared by the
manufacturer. Prior to the tests, the minimum opening time should be measured at maximum trip coil voltage
maximum pressure for operation and minimum pressure for interruption. If the minimum opening time measured
prior to the tests is lower than the one declared by the manufacturer, this lower value should be used for the
determination of the required test parameters.
NOTE 2 This definition assumes that the minimum clearing time obtained with the minimum pressure for
interruption is similar to the one that would be obtained with the maximum pressure for interruption. Normally, the
minimum clearing time is obtained with the maximum pressure for interruption. If such pressure condition is giving
a minimum clearing time such that the minimum clearing time range applicable (as given in Tables 1a to 2d of
IEC 62271-308:2002) for tests is different than the one obtained at minimum pressure for interruption, then it is
permissible to verify the minimum clearing time by using the maximum pressure for interruption.
3.18
pre-strike
voltage breakdown between the contacts during a making operation which initiates current
flow
4 Synthetic testing techniques and methods for short-circuit breaking tests
4.1 Basic principles and general requirements for synthetic breaking test methods
Any particular synthetic method chosen for testing shall adequately stress the test circuit-
breaker. Generally, the adequacy is established when the test method meets the requirements
set forth in the following subclauses.

– 12 – 62271-101  IEC:2006+A1:2010

A circuit-breaker has two basic positions: closed and open. In the closed position a circuit-
breaker conducts full current with negligible voltage drop across its contacts. In the open

position it conducts negligible current but with full voltage across the contacts. This defines

the two main stresses, the current stress and the voltage stress, which are separated in time.

If closer attention is paid to the voltage and current stresses during the interrupting process

(Figure 1), three main intervals can be recognized:

– High-current interval
The high-current interval is the time from contact separation to the start of the significant

change in arc voltage. The high-current interval precedes the interaction and high-voltage

intervals.
– Interaction interval
The interaction interval is the time from the start of the significant change in arc voltage
prior to current zero to the time when the current including the post-arc current, if any,
ceases to flow through the test circuit-breaker (see also Clause B.2).
– High-voltage interval
The high-voltage interval is the time from the moment when the current including the post-
arc current, if any, ceases to flow through the test circuit-breaker to the end of the test.
4.1.1 High-current interval
During the high-current interval the test circuit-breaker shall be stressed by the test circuit in
such a way that the starting conditions for the interaction interval, within tolerances to be
specified, are the same as under reference system conditions.
In synthetic test circuits the ratio of the power-frequency voltage of the current circuit to the
arc voltage is low in comparison with tests at reference system conditions due to:
– the voltage of the current circuit being a fraction of the system voltage;
– the fact that the arc voltages of the test circuit-breaker and of the auxiliary circuit-breaker
are added.
As a result the duration of the current loop and the peak value of the current will be reduced.
This distortion of the current is outlined in Annex A.
Considerations with respect to the arc energy released in the test circuit-breaker lead to a
maximum permissible influence in terms of tolerances on two characteristic values of the
shape of the current, i.e. current-peak value and current-loop duration (see Annex A).

The tolerance on the amplitude and the power frequency of the prospective breaking current
is given in 6.103.2 and 6.104.3 of IEC 62271-100. Therefore, the following conditions
concerning the actual current through the test circuit-breaker shall be met:
– for symmetrical testing the current amplitude and final loop duration shall not be less than
90 % of the required values based on rated current;
– for asymmetrical testing, the current amplitude and final loop duration shall be between
90 % and 110 % of the required values, based on rated current and time constant (see
Tables I.1a to I.2d 15 through 22 of IEC 62271-100:2008).

62271-101  IEC:2006+A1:2010 – 13 –

Adjustment measures:
The amplitude and duration of the last current loop may be adjusted by several means,
such as
– increasing or decreasing of the r.m.s. value of the short-circuit test current,

– changing of the frequency of the test current,

– using pre-tripping or delayed tripping,

– changing the instant of current initiation (initial d.c. component).

For reference see 5.3 of IEC 62271-308.
4.1.2 Interaction interval
During the interaction interval, the short-circuit current stress changes into high-voltage stress
and the circuit-breaker performance can significantly influence the current and voltages in the
circuit. As the current decreases to zero, the arc voltage m
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