ABB hd4 Installation And Service Instructions Manual - page 35
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SF6 in its pure state is an odourless, colourless, non-toxic gas
with a density about six times higher than air. For this reason,
although it does not have any specific physiological effects, it
can produce the effects caused by lack of oxygen in ambients
saturated with SF6.
During the interruption phase of the circuit-breaker, an electric
arc is produced which decomposes a very small amount of
SF6. The decomposition products remain inside the poles and
are absorbed by special substances which act as molecular
sieves. The probability of contact with decomposed SF6 is
extremely remote, and its presence in small quantities (1-3
ppm) is immediately noticeable because of its sour and
unpleasant smell. In this case, the room must be aired before
anybody enters it.
The strong infrared absorption of SF6 and its long lifetime in
the environment are the reasons for its high Global Warming
Potential (GWP) which is 22.800 higher than CO2, according
to the Fourth Assessment Report.
The GWP is calculated over a time period of 100-years
warming potential of 1 kg of a gas referred to 1 kg of CO2. Its
overall contribution to the global greenhouse gas effect from
all applications amounts to approximately 0,2% overall.
However, the GWP of SF6 alone is not adequate to measure
the environmental impact of electric power equipment based
on SF6 technology.
The environmental impact of any specific application
should be evaluated and/or compared using the Life Cycle
Assessment – LCA approach as regulated by ISO 14040.
11. Indications for handling apparatus with SF6
The Electric Industry utilises SF6 in a closed cycle, banking
it e.g. in gas insulated substations (GIS), medium-voltage
and high-voltage gas circuit breakers (GCB), high-voltage
gas insulated lines (GIL), gas insulated voltage transformers
(GVT). In Asia, significant quantities of SF6 are banked in gas
insulated power transformers (GIT) as well.
The Electric Industry is reported as the most important user
of SF6, worldwide. In spite of being the most important
user of SF6, the Electric Industry is a low contributor to
the global emission of SF6, far below to other industries
or users with “open application” of the gas. However, its
importance as source substantially varies from region to
region and from country to country, depending on the SF6
handling procedures adopted, the tightness of the electric
power equipment and the amount of gas banked in electric
equipment.
For info about Life Cycle Assessment of apparatus, see
document (1VCP000264).
To dispose of the SF6 gas, please contact the ABB
Assistance Service (see contact persons at http://www.abb.
com/ServiceGuide/alphabetical.aspx) as this operation must
be done only by trained and qualified personal; on request are
available specific instructions for the evacuation of the SF6
gas from the apparatuses.
The volume of SF6 in each apparatus is indicated on the
nameplate.