Due to aging and moisture

the moisture content of transformer’s oil-immersed pressboard is greatly increased. Based on the equivalent model of transformer and the dielectric response model of composite medium

meanwhile

based on laboratory data and frequency temperature superposition theory

a quantitative calculation method of moisture content in oil-immersed pressboard of transformer is obtained. In order to verify the validity of the algorithm

the moisture content of equivalent model after natural moisture absorption under variable temperature and the moisture content of equivalent model after aging test at room temperature are experimentally analyzed. The test results reveal that

for the XY model of natural moisture absorption

the results calculated by this algorithm are closer to the titration values. The accuracy of calculation results is determined by the goodness of fitting curve. For the model of aging

the result of IDAX-300 fitting algorithm is relatively high when the moisture content of the model is tested after aging at a wide frequency range. Moreover

the oil-paper insulation model and transformer scaling model under different aging conditions are tested and verified. Using the numerical iterative algorithm

we flexibly choose the computation frequency domain to solve the problem that the low molecular material product after aging will remarkably affect the test results. The numerical iterative fitting results of moisture content are closer to the real titration value.