In the research of time-division dielectric response for oil-paper transformer insulation aging diagnosis

there always exists uncertainty in the solution spectrum of the dielectric response spectra

the parameter calculation process is complex

and it is difficult to describe the physical meaning of the indirect extracted feature quantity. In accordance with the problem in the circuit model determination and the feature extraction

we propose a new method to diagnose the aging condition for transformer oil-paper insulation. Firstly

a terminal two-point analytical method of depolarization current spectrum is put forward to determine the insulation equivalent circuit for transformer oil-paper insulation

a new type of polarization maximum straight spectrum is drawn

and three new characteristic parameters

such as

the number of polarization low resistances lLow

R

the maximum slope of polarization aτmax

and the maximum intercept of polarization bτmax

are directly extracted. It is confirmed that

the more serious the aging of oil-paper insulation is

the larger the number of lLow

R

will be

and the greater value of aτmax and bτmax will be. The analysis and calculation of experimental data of several transformers prove that the aging status for transformer oil-paper insulation can be effectively diagnosed through new characteristic parameters. The new method and characteristic quantity of equivalent circuit provide a new way to diagnose the aging of oil-paper insulation.