Electric Field Analysis of 35kV Measuring Voltage Transformer with Insulation Defects

Metering voltage transformers of 35kV and below commonly adopt solid insulation structure. During the pouring process of insulation structure, defects such as bubbles and metal particles may be introduced to the solid insulation, which will cause partial discharges, and then affect the insulation and metering performance of the transformer. This paper mainly aims at the influence of the above defects on the insulation electric field of the transformer. A three-dimensional simulation model of a 35kV voltage transformer is established, and the influence of the defect type, defect location, defect size, and voltage waveform on the electric field distribution near the insulation defect are analyzed. The results show that: the electric field distortion caused by metal particles is slightly larger than that of bubbles; the insulation defect near the high voltage side of high voltage winding causes the most serious electric field distortion; smaller bubble defect causes stronger electricfield distortion, while larger metal particles cause stronger electricfield distortion. The electric field distortion laws of defects under power frequency voltage and impulse overvoltage are similar. The research of this paper can provide guidance to the production and maintenance of metering voltage transformers.