Scope of testing of breakdown voltage of insulating oils
IEC 156 insulating oil dielectric breakdown testing
Scope
This International Standard specifies the method for determining the dielectric breakdown voltage of insulating liquids at power frequency. The test portion, contained in a specified apparatus, is subjected to an increasing a.c. electrical field by means of a constant rate of voltage rise until breakdown occurs.

The method applies to all types of insulating liquids of nominal viscosity up to 350mm2s-1 at 40 degree. It is appropriate both for acceptance testing on unused liquids at the time of their delivery and for establishing the condition of samples taken in monitoring and maintenance of equipment.