The dielectric breakdown voltage is the maximum potential gradient that can withstand oil, no flashover occurs.
Indicates the presence of contaminants such as water, earth, cellulose fibers, clay, mud or conductive particles in the liquid agents.
There are two recognized for measuring the dielectric breakdown voltage in insulating oils methods:
- Flat electrodes: Recommended for acceptance testing of unprocessed insulating fluids or routine tests.
- Hemispherical electrodes: This method is more sensitive to the harmful effects on the oil as it has a more uniform electric field. This method is recommended for filtered, degassed and dehydrated oils, during and after filling of electrical equipment. It is also increasingly being used for transformers in service.