Abstract Transients produced during circuit breaker operations have undesirable consequences to the equipment itself and to the network as a whole. So to reduce or eliminate the transients, mitigation techniques should be used, analysed and optimized. One of them has emerged about 30 years ago and has proven since then to be more effective and reliable in most of the cases: Controlled Switching (CS) of circuit-breaker (CB). A part of the CS knowledge which was relatively new at that time was gathered and published more than 14 years ago by CIGRE WG A3.07 in Electra papers and in three Technical Brochures. This WG A3.07 also performed a worldwide survey of applications of controlled switching by reviewing the number of controllers supplied by major manufacturers.

1. Chapter 1 - Introduction
With increased power quality demands, rapidly
varying load patterns and never-ending grid
expansion, switching-on and switching-off operations
must be performed more frequently to control the
reactive power levels. These operations can result in
switching transients with undesirable consequences
to equipment and to the network as a whole. Mitigation
techniques must be used, analysed and optimized.
While conventional solutions provide some degree of
mitigation, CS is the most effective and reliable solution
that has been successfully deployed and validated for
nearly three decades. Taking the voltage or current as
a reference, the purpose is to open and/or close the
CB at an optimum electrical switching target dictated
by the switching load type, the CB characteristics and
the operating conditions.
From the ever-increasing installed CS systems,
successful as well as unfortunate stories can be told
[1]. The result from the survey as well as the collected
international experiences highlight the fact that our
knowledge about the controlled switching mitigation
technique has still to be improved and needs to be
disseminated.
Chapter 2 - Definitions of
terminology
To ensure consistency within this document and •••
Abstract
Transients produced during circuit breaker operations
have undesirable consequences to the equipment
itself and to the network as a whole. So to reduce or
eliminate the transients, mitigation techniques should
be used, analysed and optimized. One of them has
emerged about 30 years ago and has proven since
then to be more effective and reliable in most of the
cases: Controlled Switching (CS) of circuit-breaker
(CB).
A part of the CS knowledge which was relatively new
at that time was gathered and published more than
14 years ago by CIGRE WG A3.07 in Electra papers
and in three Technical Brochures. This WG A3.07
also performed a worldwide survey of applications
of controlled switching by reviewing the number of
controllers supplied by major manufacturers.
In 2013 a new CIGRE WG A3.35 was created to
update the knowledge. Its main goals were to collect
world-wide CS experience for different applications,
synthesize and propose optimum commissioning
guidelines, provide recommendations for the
improvement of relevant standards, and publish a
detailed guide for CS project commissioning and
follow-up in a CIGRE Technical Brochure (TB).
After four years of hard work done by 32 Members from
14 countries, the TB is now ready to be published. It is
divided in the following main chapters:
Guidelines and best practices for
the commissioning and operation
of controlled switching projects
Members
A. MERCIER, Convenor (CA), M. STANEK, Secretary (CH), F.A. ABDELMALEK (FR),
W. ALBITAR (DE), G. ANDRAE (CH), G. BLANCHET (NO), H. S. BRONZEADO (BR),
E. COWHEY (IE), J. AMON (BR), Y. FILION (CA), H. GARDUNO (SE), B. HAN (CN),
M. ILES (UK), H. ITO (JP), H. KOYAMA (JP), N.-M. NGUYEN (FR), T. OHNSTAD (NO),
U. PARIKH (IN), H.-G. RICHTER (DE), Z. SMITH (US), P. TAILLEFER (CA)
Corresponding Members
S. DE CARUFEL (CA), P. JONSSON (SE), J. LOPEZ-ROLDAN (AU), B. LOFGREN (US),
A. PANDHARKAR (IN), E. PORTALES (CA), A. ROCHA (BR), L. VIOLLEAU (FR),
C. WEEKS (US), L. XU (CN), Z.L. NAN (CN)
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2. energising the capacitor banks to reduce the restrike
probabilities.
Figure 3 - Basic principles for CS energisation
for a grounded capacitor bank
This chapter also enumerates some mitigation
techniques, focusing mainly on the CS. It details
the controlled closing notions and strategies for
a grounded and an ungrounded capacitor bank;
emphasis was put on the second one because it is
more demanding for the CB and is less well known. It
also covers the capacitor residual charge and the fast
switching application. Six case studies were selected
to give a general picture of the field experience (good
as well as unfortunate).
Chapter 5 - Controlled switching
of shunt reactors
Shunt reactors are used to compensate the capacitive
reactive power in high voltage systems (long overhead
lines, cables). They are switched frequently, on a
daily basis, giving rise to harmful transients that may
degrade the circuit breaker (Figure 4), the shunt
reactor and the power quality.
Figure 4 - Example of a SF6 CB nozzle degradation after 1500
operations with uncontrolled opening switching
Only the CS mitigation technique for the energising
(Figure 5) and de-energising (Figure 6) of a shunt
reactor is detailed in this chapter. Controlled
strategies are explained and optimal targets are
proposed. •••
with preceding publications regarding Controlled
Switching (CS) of Circuit-Breaker (CB), relevant
definitions and terminology are given in a short table.
Chapter 3 - Revision and short
upgrade of CIGRE WG A3.07
legacy
This chapter provides the history [2] [3] [4] [5] of this
relatively new mitigation technique. It also summarizes
and clarifies the CS basic notions (Figure 1).
Figure 1 - Example of a typical CS device (CSD) installation
More recently (2014), CIGRE WG A3.35 started:
“Guidelines and Best Practices for the Commissioning
and Operation of Controlled Switching Projects”.
Taking the results of preceding CIGRE WG and those
of other relevant bodies as a starting point, the WG
conducted a new international survey mainly focused
on knowledge and experience from experts with the
commissioning of past and present CS projects.
Chapter 4 - Controlled switching
of shunt capacitor banks
Shunt capacitor banks are switched multiple times
per day by system operators depending on system
voltage requirements and the daily load variations.
Without a mitigation technique, a capacitor bank that
is randomly energised can generate an inrush current
several times the nominal value and at high frequency
(several kHz) (Figure 2), as well as significant voltage
distortion in the network.
Figure 2 - Example of a peak voltage energisation of a capacitor bank
CS is mainly used during energisation (Figure 3) to
reduce inrush currents and enhance power quality
issues. But it may also be used as an option for de-
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3. Field experience (good as well as unfortunate) is
summarised in six selected case studies.
Chapter 7 - Controlled switching
of transmission lines
Without a mitigation technique, energisation and fast
re-energisation (auto-reclosing) of long unloaded
overhead transmission lines can cause undesirable
overvoltages produced by the propagation of
electromagnetic waves along the line, generally called
traveling wave phenomena [2] [6]. This overvoltage
may over-stress the air gaps between the conductor
and the transmission tower structure, leading to
flashover and failure to successfully energise the line.
Figure 8 - Reflection of traveling wave upon line energisation
Common mitigation methods are metal-oxide surge
arresters (MOSAs) [7]SRP decided to apply high
energy transmission line arresters (TLAs [8] and
CB closing resistors (PIR) [9] while CS (Figure 9) is
gaining ground because of economic and technical
advantages.
Figure 9 - CS strategy for energising a line with high degree of
shunt compensation
At present, controlled closing and reclosing on
uncompensated and shunt reactor compensated
lines has been applied in service and has delivered
the intended suppression of switching transients: four
case studies are presented.
Chapter 8 - Controlled switching
of power cables
Compared to overhead transmission lines [10],
underground and submarine cables have a much
higher capacitance per kilometer ([11], which may give
birth to some zero-missing current after energisation
(Figure 10), to low-order resonance and several
transient phenomena [12]. It is therefore highly
recommended to use proper countermeasures [13] to
avoid or mitigate them: CB equipped with pre-insertion
resistor (PIR) and CB Controlled Switching Device. •••
Figure 5 - CS strategy for energising a shunt reactor
Figure 6 - CS strategy for de-energising a shunt reactor
Nine selected case studies conclude the chapter.
Chapter 6 - Controlled switching
of power transformers
Potential problems may arise when energising
transformers. While ferroresonance and sympathetic
interaction problems are summarized, focus is given
to the inrush current and temporary overvoltage
problems.
The use of CS mitigation technique poses a different
challenge from other usual CS applications, since the
optimal closing target that prevents core magnetic
saturation is not the same for each operation
and depends on the prevailing conditions in the
transformer iron core (residual flux) at that particular
moment (Figure 7). The challenge is greater when a
gang operated CB is used: another CS strategy must
then be used.
Figure 7 - Example of CS strategy for energising the first phase of
an unloaded power transformer
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4. Chapter 10: Type tests, Factory
tests and CB suitability
evaluation
CIGRE WG13.07 published in 1999 an application
guide for CSS [2] based on international surveys of
field experience. It proposed testing requirements
and their procedure for the components and
integrated system (CSS).
Since then, reviewing results of evaluation tests
and field tests conducted according to CIGRE
recommendations confirmed the effectiveness of the
CIGRE requirements and the procedures. However,
some clarifications and recommendations have
been added. In summary, the components used
for CSS are normally tested in the factory as a part
of the routine and type tests. Factory testing items
for Circuit Breakers include electrical performance
tests as well as mechanical performance tests. The
controller and the related sensors are tested to
verify its functions and electromagnetic, seismic and
environmental compatibilities. Finally, the controlled
switching performance with the integrated system
should be demonstrated. More precise details are
given in the chapter “Qualification and Standards” of
this Technical Brochure.
A case study has been included to pinpoint the
fact that some phenomena observed during factory
testing will never appear in live field switching. This
may mislead the configuration of the CSD adaptation
function; the configuration should then be validated
and adjusted at commissioning with live tests.
Chapter 11 - Commissioning of CSS
The vendors and suppliers provide guidelines for their
Controlled Switching System (CSS). Whilst there
are similarities in the processes and procedures for
commissioning the CSS, there is a need for updated
guidelines in support of the best commissioning
practices by reflecting the recent field experience
with CSS.
For a system like CS that is so closely linked to the CB
and switched equipment, methodical commissioning
is of the utmost importance to ensure optimal long-
term operation. During the commissioning tests,
overall equipment performance and the operating
parameters used by the CSD are tested and
validated live. Five case studies of commissioning
practices are described to help prepare a proposed
commissioning checklist. •••
Figure 10 - Example of a 100% compensated cable
energisation current
A single case study is given at the end of the chapter.
Chapter 9 - Controlled switching
survey
Working Group A3.07 published in 2004 a worldwide
survey of applications of controlled switching. Fifteen
years later, a new survey (Figure 11) from WG A3.35
was necessary to validate the original projected number
of installations of this relatively new technology. The
covered period ranges from the years 2002 to the end
of 2015. The survey also tried to identify the evolution
(knowledge increase and feedback) of controlled
switching as well as the actual needs. The survey was
divided in two parts, one for the manufacturers and
one for the users.
Figure 11 - Combined WG A3.07 and WG A3.35 survey results on
the CS installations
Statistical results and summary of anonymous
replies are published in this section. 42 complete
replies were received from four continents (North
America, Asia, Europa and Oceania).
To collect further international experience and
knowledge, WG A3.35 completed an international
literature survey, published from 2002 to 2018.
More than 500 publications have been collected and
analysed, of which around 40 are a Ph.D. or M.S.
thesis.
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5. previously reserved to Protection and Control
engineering relays or dedicated monitoring devices,
resulting in additional system safety given by
increased redundancy.
The more comprehensive monitoring throughout
the product’s entire life cycle results in performance
based maintenance, potentially reducing the
likelihood of a negligence-based malfunction.
Controlled switching, when applied correctly, will
provide a silent feedback, alarming only in case of a
malfunction, and will usually self-adjust by means of
adaptive functionality [3].
Chapter 15 - Recommendations
and conclusion
Controlled switching mitigation technique has
already been widely applied by many utilities. Nearly
three decades of experience have proven that it is
an elegant and highly stable solution for mitigating
CB switching transients.
Before recommending the CS solution, all the
necessary information should be available for the
end-user to evaluate the adequacy of the device
characteristics with their own operation environment.
It may also be necessary to run some simulations
studies to better evaluate the benefits of such a
solution for different applications and to compare it
with other alternatives.
To reap the advantages of reduced transients,
a methodical commissioning where operating
parameters are customized and their performance
tested is of the utmost importance.
A new standard is needed for CB mainly used for
the implementation of CS. It should address the
requirements for such applications, considering two
basic system configurations:
• CB supplied and tested independent from any
particular controller,
• CB supplied and tested with a dedicated controller,
necessary sensors and auxiliary equipment
which form part of the tested equipment.
In order to proactively prevent unplanned down time,
users should take advantage of the CSD’s integrated
monitoring elements to indicate inappropriate
equipment behaviour with greater accuracy and
confidence, and trigger the appropriate maintenance
action before a problem escalates. Furthermore,
CSD data collected from various sites can provide
a powerful learning tool for the next generation of
technical experts and increase the knowledge base
of the global community. •••
Chapter 12 - Qualification and
standards
Since there is no standard dedicated to CSD or
CSS, with algorithms used being vendor specific, the
purpose of this chapter is to compile a list of existing
regulations/standard bodies. The goal is to deliver
some recommendations to select an appropriate
frame to the intended use and qualification of a CSS.
IEC produced in 2010 a technical report (IEC/TR
62271-302) to provide “guidance on the design,
construction, specification and testing of circuit
breakers with intentional non-simultaneous pole
operation which are excluded from the scope of IEC
62271-100” [14]. This IEC technical report will be
converted into a standard in 2019 by the IEC SC 17A/
WG 61, using some recommendations described in
the present TB.
Their definition of a controlled switching system
(CSS) is the combination of circuit breaker, controller
and necessary sensors and auxiliary equipment
required to achieve controlled switching. So the
chapter is divided in three parts:
• qualification of controlled switching systems,
• instrument transformer,
• communication protocol.
Chapter 13 - Simulations studies
related to controlled switching
Before recommending CS solution, it may be
necessary to run some simulations studies to better
evaluate the benefits of such a solution for different
applications and to compare it with other alternatives.
This section aims at giving some advice on how
system studies should be performed to assess the
performance of such a technique depending on the
goal to be achieved. Component models such as
circuit breakers, power transformers, overhead lines
and cables, shunt reactors, etc. are also discussed.
For each application, a simulation case study along
with its results are provided.
Chapter 14 - Follow-up and
monitoring
Electric power equipment maintenance has
historically been time based; however, empirical data
reveals that in the majority of cases, maintenance
is of a corrective nature, rather than preventive. In
order to proactively prevent unplanned down time,
and taking advantage of current development(s)
in computational power, the latest generations of
CSD have integrated several monitoring elements
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6. Exposition, 2014.
[8] B. Filipović-Grčić, I. Uglešić, and I. Pavić, "Application of
line surge arresters for voltage uprating and compacting
of overhead transmission lines", Electr. Power Syst. Res.,
vol. 140, pp. 830–835, Nov. 2016.
[9] L. He and R. Voelzke, "Effects of pre-insertion resistor on
energization of compensated lines", presented at the IEEE
Power and Energy Society General Meeting (PESGM),
2016.
[10] CIGRE WG C4.502, Power system technical performance
issues related to the application of Long HVAC cables.
CIGRE Technical Brochure 556, 2013.
[11] H. Khalilnezhad, M. Popov, L. van der Sluis, J. P. W. de
Jong, N. Nenadovic, and J. A. Bos, "Assessment of line
energization transients when increasing cable length in
380 KV power grids", presented at the IEEE International
Conference on Power System Technology (POWERCON),
2016.
[12] C. L. Bak, "EHV/HV Underground Cable Systems for
Power Transmission", PhD Thesis, Department of Energy
Technology, Aalborg University, 2015.
[13] H. Khalilnezhad, M. Popov, L. van der Sluis, J. A. Bos,
J. P. W. de Jong, and A. Ametani, "Countermeasures of
Zero-Missing Phenomenon in (E)HV Cable Systems", IEEE
Trans. Power Deliv., no. 99, 2017.
[14] "IEC/TR 62271-302 High-voltage switchgear and
controlgear – Part 302: Alternating current circuit-breakers
with intentionally non-simultaneous pole operation". IEC,
Jun-2010. 
References
[1] De Carufel, S. et al., "Special Considerations with
Controlled Switching Projects", presented at the CIGRE
Colloquium, Nagoya, Japan, 2015.
[2] CIGRE WG 13.07, "Controlled switching of HVAC circuit-
breakers. Guide for application lines, reactors, capacitors,
transformers. Ist part.", ELECTRA, no. 183, pp. 43–73, Apr.
1999.
[3] CIGRE WG A3.07, "Controlled Switching of HVAC CBs:
Benefits & Economic Aspects", CIGRE Technical Brochure
TB-262, 2004.
[4] CIGRE WG 13.07, "Controlled switching of HVAC circuit-
breakers. Guide for application lines - reactors - capacitors
- transformers. 2nd Part.", ELECTRA, vol. 185, pp. 37–57,
1999.
[5] CIGRE WG A3.07, "Controlled Switching of HVAC CBs
- Guidance for Further Applications Including Unloaded
Transformer Switching, Load and Fault Interruption and
Circuit-Breaker Uprating", CIGRE Technical Brochure TB-
263, 2004.
[6] R. Smeets, L. van der Sluis, M. Kapetanović, D. F. Peelo,
and A. Janssen, "Switching Overvoltages and their
Mitigation", in Switching in Electrical Transmission and
Distribution Systems, John Wiley & Sons, Ltd, 2014, pp.
310–346.
[7] P. Bunov et al., "Transmission line arresters application for
control of switching overvoltages on 500-kV transmission
line", presented at the IEEE PES T&D Conference and
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