For test operations according to the liquid dielectric breakdown voltage measurement method we use high voltage machines that consist of high-voltage step-up transformer, voltage rise block, test cell with electrodes and so on. Described dielectric oil's test machine UIM – 90 with electromechanical voltage rise block. Cause of hard requirements in specification documents about voltage sine wave form on cell's electrodes, we performed field tests for UIM – 90 that help to evaluate the mains voltage impact on the test voltage distortion and measurement accuracy. Was discovered that during usage of electromechanical voltage rise block voltage steps disrupt sine wave’s form proportionally to step-up transformer’s transformation coefficient. Performed analysis of this block’s construction and established that usage of ЛАТР and mechanical voltage controller could lead to additional sine’s wave disruption. Decided to develop electronic voltage rise block which will allow to get rid of mains influence on test data. Created the algorithm of wave shaping from microcontroller, which generates voltage ramp to the amplifier representing pulse width modulator, then to the step-up transformers cascade. Proposed to use additional transformer for level matching of amplifier’s output voltage and main high voltage transformer’s input voltage. Presented flow sheet for UIM – 90 with electronic voltage step-up block and cascading start ofstep-up transformers. Provided voltage oscillograph trace and it spectrograph on the main transformer’s primary side, received due to the implementation of developed electronic voltage step-up block, prove that voltage sine wave form doesn’t rely on mains quality. After upgraded UIM – 90 and it world analogues technical parameters analysis we could make a conclusion about it competitive capability on global level.
Influencing Factors on the Dielectric Breakdown Strength in F-gas Free High-voltage Switchgear