User manual SEFELEC 5x Series 186 v1.06
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 insu-
lating material, between 2 conductive parts, to avoid breakdown.
• LEAKAGE CURRENT: Steady current flowing in an insulating material subject to high volt-
age.
• BREAKDOWN: The immediate break of the dielectric property of an insulating material. Eve-
ry 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 insu-
lating material occurs and the distance between the two points subject to the voltage (gener-
ally given in kV/cm). Regarding the insulating material type (solid, liquid or gas) a dielectric
break can be: a perforation, a flash over or an arc.
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