Recent Researches in Environment, Energy Systems and Sustainability
Environmental Pollution Caused by Electrical Power Devices
JOŽE PIHLER
Power Engineering Laboratory
University of Maribor, Faculty of Electrical Engineering and Computer Sciences
Smetanova 17
SLOVENIA
joze.pihler@uni-mb.si
Abstract: - This paper deals with environmental pollution caused by the operation of electrical power devices.
This pollution can occur either during normal operation or in the cases of failures or mistakes. Such
environmental pollution can be reduced and, in some cases, fully prevented by the adequate awareness of
individuals, responsible behaviour by the consumers and manufacturers of these devices, and by adequate
legislation and standards by governments and professional associations. This paper presents some concrete
proposals from the field of medium and high voltage power devices.
Key-Words: - electrical power apparatus, devices, insulation media, arc-extinguishing medium, pollution,
ecosystems
presents the insulation, cooling, and arcextinguishing media. Section 3 deals with those
methods that could prevent environmental pollution
caused due to the operation of electrical power
devices. Special emphasis is given to improving
environmental impacts during the operation of
power devices based on SF6 gas. Practical
possibilities are given especially within the medium
of voltage devices and apparatus. Section 4 contains
the conclusion.
1 Introduction
Electrical power apparatus are basic elements within
any electrical power system. They exist in power
plants, as 400, 220 or 110 kV transmission
networks, connected to 110, 20 or 10 kV
distribution networks through substations. The latter
are through distribution substations connected to the
low voltage electricity networks of consumers. In
addition to the abovementioned, there are also many
substations with electrical power devices within
industrial and other electricity consumers` internal
networks.
Electrical power devices and apparatus consist of
electricity-conducting parts, and insulation-parts,
that separate the conducting from the earthed parts.
The earthed-parts are those protective elements or
housings that prevent people when handling their
devices from coming into direct contact with the
energised parts of electrical power devices. At the
same time their role can also be to prevent failures,
such as line to ground faults, throughout the grid or
to other devices.
The insulation parts can be made of solid, liquid
or gaseous dielectric materials. Insulation materials
can have an important impact on the functional
operation of a device, for example as an arcextinguishing medium.
This paper deals with the possibility of replacing
electrical power devices` insulation material and
thus reducing or preventing environmental
pollution.
Section 2 describes the impact of electrical
power devices` operations on the environment. It
ISBN: 978-1-61804-088-6
2 Impacts of electrical power devices`
operations on the environment
Each electrical power device consists of individual
elements, such as switches, fuses, surge arresters,
insulation elements (insulators and bushings),
switchgear, i.e. the housing where all these elements
are mounted, conductors or bus bars connecting
conductive parts and insulation medium. Electrical
power devices can basically be divided into devices
for indoor and outdoor usages. These devices are
considerably different with regard to voltage-levels
and insulation media. Low voltage devices of up to
1 kV are mainly air-insulated. Medium voltage
devices up to 35 kV are air-insulated, as shown in
Fig. 1, or are SF6 insulated.
Both low and medium voltage devices for indoor
use are placed within areas that are either parts of
other buildings or are individual buildings. For
outdoor devices single-elements are used that have
to comply with the requirements for outdoor usage,
especially regarding atmospheric conditions. They
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Recent Researches in Environment, Energy Systems and Sustainability
extinguishing media. In switch-disconnector and
older circuit-breakers this is compressed air. In other
switch-disconnectors an important role is played by
arc-extinguishing chambers with solid insulation
materials. These insulation materials were gasified
and ultimately extinguished the electrical arc (Fig.
2).
are placed on various poles or on special
constructions. High voltage devices above 110 kV
are those devices that are air-insulated as individual
elements, and are used outdoor. They can also be
SF6 gas-insulated and used indoors. Switchingoperative devices are needed for performing their
principal task – interruption of an electrical current
– the arc-extinguishing medium. The latter can be
air, oil, or of various gases. Important elements of
electrical power systems are also power
transformers and measurement transformers. They
also need insulation and cooling media, which can
be either air, oil, or various gases.
Fig. 2: Switch-disconnector with arc-extinguishing
chambers made of solid dielectric materials.
SF6 gas was introduced, as an upgrade of these
switch-disconnectors. During the development of
circuit-breakers arc-extinguishing chambers firstly
phase contained compressed air and transformer oil.
In the first phase of development this chamber was a
vessel in which the device was submerged. During
the development continuation phases, the arcextinguishing chambers were separately, topped-up
with oil for each phase. As a result of this
development work a low-oil circuit-breaker
appeared (apparatus shown in Fig. 1). The essential
advantage of such a device is that it is less harmful
to the environment due to its significantly-lower
quantity of oil. In Europe such devices are still
massively used, although they are no longer
installed in new buildings. Vacuum circuit-breakers
within the middle-voltage area and SF6 circuitbreakers within medium voltage area followed on
low-oil circuit-breakers in Europe. In America, and
partly in the UK, these circuit-breakers were the
successors of compressed-air circuit-breakers.
During the first period of development in Europe
low-oil circuit-breakers were deployed at the 110
kV voltage level in the high voltage area. Many of
these circuit-breakers are still in operation. SF6
circuit-breakers became the successors of these
devices.
Switchgears were, in the early-phases of their
usage, almost exclusively air-insulated. In later
years, manufacturers started to add various solid
dielectric materials composed of duroplast or
thermoplast materials as walls for separating
Fig. 1: Air-insulated metal-clad switchgear within
insulation walls, and a low oil circuit-breaker.
2.1 Insulation, cooling, and arc-extinguishing
media of electrical power devices
Electrical devices can have harmful impacts on the
environment in those cases of non-operational,
normal operation, and malfunctioning. These
harmful impacts can be caused by cooling,
insulation, and arc-extinguishing media. An
example is transformer oil. Conventional
transformer oils were inflammable and poisonous.
When leaking into the environment, they caused
environmental pollution and became a danger to
living creatures. Today's mineral synthetic oils,
however
do
have
significantly-improved
characteristics.
Switching devices at all voltage levels interrupt
and re-connect electrical circuits. These chambers
make sure that the electrical arc is extinguished at a
predefined time, which ultimately interrupts an
electric current. An essential role is played by the
arc-extinguishing medium. There are several
methods for extinguishing and various arc-
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Recent Researches in Environment, Energy Systems and Sustainability
amounts to 6,135 kg/m3. SF6 has an approximately
five-times higher density than air, which means that
it tends to accumulate within lower-lying areas, such
as cable canals or vessel-bottoms. If larger amounts
of this gas accumulate with closed-areas, there is a
danger of suffocation.
The dielectric strength of SF6, is under the same
conditions, approximately 2.5-times higher than for
air, which means that the sizes of the devices can be
2.5-times smaller. At a pressure of 300 kPa, SF6 gas
insulates better than oil.
SF6 gas has certain disadvantages, such as:
• As insulation medium it is sensitive to
appearance of points with high electric field
strength, therefore it is very important that
surfaces are smooth and high quality
processed;
• As arc-extinguishing medium it forms during
the burning phase of electric arc some
products that are for long time poisonous for
living beings;
• SF6 is a greenhouse gas and has the highest
greenhouse potential of all greenhouse gases,
amounting to 23,900 (which means that 1 kg
of SF6 has the same greenhouse effect as 23.9
tonnes of CO2). In addition to this, SF6 has a
very long atmospheric lifetime, ranging from
a few thousands to more than ten thousand
years (the longest atmospheric lifetime has
CF4, which stays in the atmosphere for up to
50,000 years).
Because of the abovementioned disadvantages and
massive use in electrical power devices there have
been some initiatives in the recent years to limit the
use of SF6, to prevent its leakage, to capture all SF6
from decommissioned devices and to replace SF6
with other gases having lower greenhouse potential.
individual switchgear elements, as shown in Fig. 1.
The positive effect was to reduce sizes. On the other
hand, the negative effect was ozone production
during normal operations, respectively causing
burning and fires in the event of failures. SF6 gas
was introduced during the 1990`s as an insulation
medium in medium-voltage switchgears, which led
to a significant reduction in the devices' sizes. The
disadvantage of using SF6 gas was the pollution of
environment, and negative impact on living beings.
When speaking about environmental pollution it
is necessary to mention the so called
electromagnetic pollution. This refers to the impact
of electrical and magnetic fields on living beings.
There have been many theoretical and practical
discussions about this issue. The European Union
itself and individual Member States have imposed
legal obligations about the maximum permitted
values of electrical field strengths and magnetic flux
densities in new buildings. This area also includes
the operation of electrical power networks, where
partial discharges occur in the forms of visible and
audible corona. These discharges appear due to the
improperly-designed individual elements of devices
and conductors. Due to high-frequencies they
strongly affect the wellbeing's of nearby residents.
Qualities of their lives are greatly reduced.
In continuations, a short presentation of today`s
most widely-used insulation and arc-extinguishing
medium SF6, is given.
2.1.1 SF6 gas as an insulation and arcextinguishing medium
Sulphur hexafluoride (SF6) is an almost ideal gas for
usage in high voltage switchgear equipment and
metal-clad systems. It has excellent electrical
(insulation and extinguishing of electric-arcs) and
thermal properties. SF6 gas is produced by a direct
chemical reaction between molten sulphur and
fluorine, which is produced by the electrolysis of
HF acid. The properties of produced gas have to
comply with the requirements of IEC 60376 [1],
which defines the permitted levels of impurities.
The annual worldwide production of this gas is
between 4,000 and 8,000 tonnes. The main use of
this gas is as a filling in switching-devices.
The technical advantages of SF6 insulated
switching-devices are generally well-known:
insensitivity to environmental impacts (dirt,
moisture, access to animals, etc.), safety for people
working with them, long-lifespans, very little
maintenance needed, small sizes, etc.
Pure SF6 is a non-poisonous and inflammable
gas without colour and odour. Its density at 20 °C
within an atmospheric pressure of 0.1013 MPa
ISBN: 978-1-61804-088-6
3 Prevention of environmental
pollution caused by electrical power
devices
Electrical power devices are the most important
parts of electrical power systems. They have to
operate reliably and continuously. The total
prevention of environmental pollution due to their
operation is impossible. Nevertheless, it is possible
to reduce it and in some cases even to prevent
harmful impacts on the environment. The most
important thing is to be aware of this fact and to act
towards achieving this objective. This is a difficult
task in this global world that is dictated to by
multinational companies that have only one
objective: to maximise their profits. An important
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Recent Researches in Environment, Energy Systems and Sustainability
role in this should be played by governments,
professional associations, and nongovernmental
organisations (NGOs).
A possibility positive action towards the
prevention of environmental pollution is discussed
below in the case of using harmful SF6 gas as an
insulation and arc-extinguishing medium. The focus
of this discussion is on medium-voltage devices. In
high-voltage devices for outdoor usage air-insulated
devices represent an alternative to SF6-insulated
ones. This is unfortunately impossible in densely
populated areas. High-voltage SF6 circuit-breakers
still have no alternative.
3.1.2 Research & Development organisations
New devices are being developed and designed
especially in the field of medium voltage devices,
where gas as an insulation medium is replaced by
solid dielectrics and by a vacuum in combination
with dry air and with solid insulation materials as an
arc-extinguishing medium. In Japan [9] they use a
special kind of resin for the fixed and silicone for
the moving parts, which has led to a reduction in
size for 25 %.
Japanese, and some European researchers, [10]
studying the possibility of SF6 gas usage by adding
other gases, such as helium, nitrogen, hydrogen,
etc., both as arc-extinguishing and insulation
mediums. The best results regarding insulation
properties are being achieved by helium (Fig. 3).
3.1 Mitigation of environmental impacts
during the operation of SF6-insulated
electrical power devices
Professional associations, civil, and NGOs in
Europe, America and Japan share the same opinion
about the harmful impact of SF6-gas on the
environment. Nevertheless, each sees their own way
of solving the problem. Some thoughts and facts are
presented in the continuation.
3.1.1 Governmental level
In Europe especially there are increased activities at
the governmental level. These activities mostly
comprise the adoption of legislation (directives and
regulations [2], [3], [4]), the aims of which are to
make manufacturers and buyers aware of certain
facts regarding SF6 gas. Some regulations already
exist about the requirements for reducing the usage
of SF6 and how to achieve this goal. In some areas
the use of SF6 gas is already prohibited and there are
sanctions prescribed for breaching these provisions.
The area of usage within electrical power devices is
not yet one of them.
In the field of standardisation (national,
European EN and international IEC) [1],[5],[6],[7]
there are already have some valid documents –
standards that more or less-precisely define the use
of SF6, by giving instructions for the designing of
devices using this gas, monitoring of the operations,
and for decommissioning after the ends of their
lifespans.
As is evident from American Standards, at the
moment they are in a phase of adopting adequate
standards that define this area in detail.
Nevertheless, they already have some IEC standards
that are more or less recommendations, but give
only mild warnings to manufacturers and buyers
about the issue of using SF6 gas [8].
ISBN: 978-1-61804-088-6
Fig. 3: Dielectric strengths [V/m] of various
mixtures of SF6 and helium in the case of an
electrical arc with an arc tube of 2.5 mm.
3.1.3 Manufacturers of switching-devices and
apparatus
Manufacturers of switching-devices and apparatus
are divided into two groups. In the first group there
are manufacturers who still produce mediumvoltage devices with SF6 as insulation and an arcextinguishing medium, and take the position that
there is no need to stop or reduce the usage of this
technology. The other group consists of
manufacturers who have never used this technology
(Northern Europe) or are switching to other
technologies, which is clearly the case in Japan and
some other parts of the world. An interesting
alternative to medium-voltage SF6 devices is thus
being offered by those producers who make dry-air
and solid insulation materials as an insulation
medium (Fig. 4). Their sizes are even smaller than
in the case of SF6 switchgear blocks.
3.1.4 Professional associations
Professional associations (CAPIEL, EPA…)
[11] channel their efforts into making
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Recent Researches in Environment, Energy Systems and Sustainability
and synthetic oils that are much less harmful to the
environment.
manufacturers and buyers aware about the
importance of careful and safe-handling
regarding SF6 gas, and the need to reduce
unnecessary and adverse emissions of SF6 gas
into the environment. They also place a great
emphasis on safely decommissioning these
devices after the ends of their lifespans.
4
Fig. 4: RMU switchgear-block with dry-air and
solid insulation materials as an insulation medium.
3.1.5 Environmental associations
Environmental Associations claim that the
usage of materials such as SF6 gas should be
stopped immediately.
References:
3.2 Mitigation of environmental impacts
caused by electrical power devices by other
insulation, cooling, and arc-extinguishing
media
[1] IEC 60376:2005, Specification of technical
grade sulphur hexafluoride for use in electrical
equipment.
[2] REGULATION (EC) No 842/2006 OF THE
EUROPEAN PARLIAMENT AND
OF
THE COUNCIL of 17 May 2006, on certain
fluorinated greenhouse gases
[3] COMMISSION REGULATION (EC) No
1494/2007 of 17 December 2007 establishing,
pursuant to Regulation (EC) No 842/2006 of
the European Parliament and of the Council,
the form of labels and additional labelling
requirements as regards products and
equipment containing certain fluorinated
greenhouse gases.
[4] COMMISSION REGULATION (EC) No
1493/2007 of 17 December 2007 establishing,
pursuant to Regulation (EC) No 842/2006 of
the European Parliament and of the Council,
the format for the report to be submitted by
The insulation and arc-extinguishing media of
medium voltage circuit-breakers are, in most cases
vacuum, as it has replaced the environmentallyproblematic transformer oil. Some manufacturers
still manufacture SF6 circuit-breakers. Even in
switch-disconnectors that contained transformer-oil,
it has been replaced arc-extinguishing chambers by
vacuums.
In switchgears, insulation-walls (Fig. 1) made of
plastic materials have been replaced by metal-clad
cells with metal walls. This is an essential advantage
especially in the cases of failures. It is almost
impossible for these materials to burn, since any
short circuit fault turns into a line-to-ground fault
(metal partition wall is earthed), and a protection
system within a minimum possible time, switches
the device off.
Conventional transformer oils in power
transformers have been replaced by modern mineral
ISBN: 978-1-61804-088-6
Conclusions
This paper dealt with those harmful impacts to the
environment that can be caused by the operation of
electrical power devices and apparatus. An
important conclusion is that these impacts can be
mitigated or even prevented, although these devices
keep operating reliably without interruptions. It is
very important to take into consideration the
research and development achievements of science
and those researchers who work for the
manufacturers of electrical power equipment. An
important role in this can also be played by
governments, which have to adopt adequate
legislation to incentivise, and in some cases, even
force manufacturers and users not to forget the
environmental protection aspect of their business
decisions.
At medium-voltage levels, SF6 gas may be
prohibited for use in switchgear. However, there are
solutions to the full replacement of SF6 gas as
insulation and as an arc-extinguishing medium. In
high-voltage switchgear the amount of gas SF6
could be reduce by adding helium and nitrogen.
Further improvement could also be achieved by
preventing the release of SF6 gas during the
operating of circuit-breakers.
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Recent Researches in Environment, Energy Systems and Sustainability
producers, importers and exporters of certain
fluorinated greenhouse gases.
[5] IEC/TR 62271-303 (2008-07) High-voltage
switchgear and controlgear - Part 303: Use and
handling of sulphur hexafluoride (SF6).
[6] IEC 60480:2004 - Guidelines for the checking
and treatment of sulphur hexafluoride (SF6)
taken from electrical equipment and
specification for its re-use
[7] IEC/TR 62271-303 (2008-07) Ed. 1.0 Bilingual
High-voltage switchgear and controlgear - Part
303: Use and handling of sulphur hexafluoride
(SF6).
[8] IEEE Std C37.122-1983, IEEE Standard for
Gas-Insulated Substations, Sponsor Substations
Committee of the IEEE Power Engineering
Society Approved December 2, 1993 (Revision
of IEEE Std C37.122-1983, includes IEEE Std
C37.122a-1991).
[9] J. Sato, O Sakaguchi, N. Kubota, New
technology for medium voltage solid insulated
switchgear, Transmission and Distribution
Conference and Exhibition 2002: Asia Pacific.
IEEE/PES, Vo. 3 pp. 1791-1796, 2002.
[10]Hiromi Odaka, Masayuki Taki, Hitoshi
Mizoguchi, Satoru Yanabu, Discussion about
an Application of CF3I gas as a substitute gas
for SF6 gas, ISSN: 0385-4213, vol. 126, no.5,
pages: 545-549(2006), Japan.
[11] CAPIEL - Co-ordinating Committee for the
Associations of Manufacturers of Industrial
Electrical Switchgear and Controlgear in the
European Union.
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