Accurate measurement and effective analysis of the space electric field and charge characteristics within the oil–pressboard insulation structure of converter transformer are essential for achieving precise insulation structure design. Presently

most electric field measurement methods relying on the Kerr electro-optical effect are limited to single-point measurements. Given the complexity of converter transformer insulation structures

including their large scale and the use of various materials

existing technologies and findings struggle to provide comprehensive electric field observations within the oil–pressboard region. After leveraging the Kerr electro-optic effect

a high-precision 32-unit photodetector array has been developed to achieve regional measurements of spatial-temporal electric field in oil–pressboard insulation. The array boasts a measurement spatial resolution of 1.4 mm2 and a sensitivity of 0.15 kV/mm

ensuring measurement accuracy exceeding 96.50%. Through practical measurements of the spatial electric field distribution within the oil–pressboard insulation under direct current voltage

the non-uniform distribution of the electric field is effectively captured in oil. Notably

the maximum deviation in field strength at different positions within the transformer oil can reach 18.5%. Moreover

as the applied voltage increases

the unevenness coefficient of the field strength gradually rises

peaking at 1.19

which signifies a progressive expansion in the area affected by electric field distortion. By conducting tests to assess the dispersion of volume resistivity in samples from various positions within large sheets of pressboard

the variation in volume resistivity of materials is posited as one of the contributing factors to the non-uniform distribution of electric field within the oil. The detailed accomplishments aim to provide essential technical and theoretical support for optimising insulation structure design of converter transformers.