XS series operating manual
XS user manual v0.55 - 132 -
13 APPLICATION NOTES
Why dielectric tests ?
The dielectric tests are performed in order :
to detect manufacturing fault on electrical equipment
to verify the quality of the insulating material of an electrical equipment
to verify that an electrical installation has been correctly done
to control the insulation resistance of an equipment or an installation to trace its changes during the
years.
Dielectric tests consist of both insulation resistance measurements and dielectric strength tests.
Glossary of terms
LEAKAGE DISTANCE : The smallest required distance, measured on the surface of the insulating
material, between 2 conductive parts, to avoid breakdown.
LEAKAGE CURRENT : Steady current flowing through an insulating material subject to high voltage.
BREAKDOWN : The immediate break of the dielectric property of an insulating material. Every
breakdown creates more or less damages to the insulating material. The breakdown tests can be
therefore destructive or not.
INSULATION RESISTANCE : Characteristic of an insulating material that being subject to a voltage,
shows a resistance such as the value of the leakage current which flows through it stays within
acceptable limits.
DIELECTRIC STRENGTH : Ratio between the voltage at which a dielectric break of the insulating
material occurs and the distance between the two points subject to the voltage (generally given in
kV/cm). Regarding the insulating material type (solid, liquid or gas) a dielectric break can be : a
perforation, a flashover or an arc.
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