Stirring effect in dielectric liquids breakdown voltage determination

The latest version of the standard IEC 60156 “Insulating liquids - Determination of the breakdown voltage at power frequency - Test method” was published in August 2018 as Edition 3.0. This standard follows the two previously published versions in 1963 and 1995. The test method described in practically all IEC 60156 versions defines a procedure in which the insulating liquid is subjected to an increasing AC electrical field until breakdown occurs and it is used for both 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. In this paper the experimental results of 50 Hz breakdown voltages of both mineral and natural ester liquids performed following the tests methods described in the new edition of IEC 60156 are shown. The tests were performed also with the use of different stirring systems.