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7.2
Liquid materials
The following sections base on the international standards for analysis of the
loss characteristics and permittivity of liquid electrical insulation like
ASTM D924-08.
7.2.1
Preparation of liquid material test cells
Cleaning the test cell is or paramount importance when measuring the dielectric
characteristics because these characteristics are defected by the presence of
conductive contaminations or moisture on the test cell surfaces. For this reason
clean and dry the test cell or minimum the contact surfaces prior testing.
7.2.2
Preparation of liquid test material and filling the test cell
eparation of liquid tes
Store the l
Store the liquid test m
Store the liquid test material in its original sealed container and protect it against
light. Some liquids
light. Some liquids, such as oils of petroleum origin, change when exposed to
sunlight. Allow t
sunlig
sunlight. Allow the sealed container to stand in the room in which the test will be
made
made for a s
made for a sufficient period of time to guarantee that the liquid test material has
the same
the same room temperature before it is opened.
When
When insulating liquids are heated to high temperatures, some of their dielectric
cha
characteristics changes with time. It is possible that this changes will influence
the measurement results. It is therefore necessary to hold the time, needed for
the liquid test material to attain temperature equilibrium with the test cell, to a
minimum. It is essential, therefore, that the procedures described in the
international standards for general and routine testing the dielectric characters
of liquids are closely followed.
In general, always rinse the test cell with a portion of the liquid test material to
be tested before the test cell is filled.
NOTICE
Follow the cleaning, warning and safety instructions of the test cell manual.
The used solvents or cleaning agents must previously been checked to
ensure that they do not contain contaminations which can influence the
measurements. Ensure that the used solvent or cleaning agent leads to
correct results of known low permittivity and dielectric losses. Some
cleaning procedure examples can be found in the international standards
like ASTM D150-11 or IEC 60250.
DANGER
Death or severe injury caused by fire, poisoning or chemical burn
vere injury caused b
Ensure the safety conditions for using solvents. Protect the personal and
the safety condition
equipment against fire and toxic effects. Read the safety instructions of the
ent against fir
solvent or cleaning agent before cleaning.
or cleaning ag
ion of liq
ight. Some
Preparation of test material and test cell
t surfaces prior testing.
surfaces prior testing.
ructions of the test c
st previously been
tions which c
sed solvent or clean
mitti
nd d
can be
in
C 60250
h
easuring the dielectric
g the dielectric
cted by the presence of
e presence o
l surfaces. For this reason
For this reas
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