To address the susceptibility of traditional quantification of moisture content in oil‑impregnated transformer paper insulation using dielectric spectroscopy features at specific frequency points to measurement errors

a frequency‑domain secondary differential spectrum method is proposed for identifying the parameters of transformer extended Debye equivalent circuit. First

the parameters of the extended Debye equivalent circuit are used to expand the characteristics of the imaginary part of complex capacitance and construct an integral spectrum of the imaginary part of complex capacitance. Second

the influence of measurement errors at different frequency points and regions on the integral spectrum of the imaginary part of complex capacitance is investigated. Finally

an evaluation method for quantifying moisture content in the paper insulation based on characteristic values of the integral spectrum is proposed. The results indicate that there is an exponential relationship between the moisture content in the paper insulation and the characteristic values of the integral spectrum of the imaginary part of complex capacitance. Measurement errors at different specific frequencies and frequency bands have little effect on the evaluation results when the integral spectrum is used to quantify moisture content. The proposed integral spectrum therefore demonstrates strong interference immunity and robustness.