Degree of polymerisation estimation for insulation paper immersed in silicone oil using frequency domain dielectric spectroscopy

Frequency domain dielectric spectroscopy(FDS)is an effective method reflecting the changes of ageing status of silicone oil‐immersed insulation paper.For better evaluating the ageing status of silicone oil‐immersed insulation paper,an evaluation method was studied by analysing the ageing kinetic model and results of FDS.First,the method to separate the different polarization losses and conductivity loss from the results of FDS was studied.Then,based on the idea of ageing correction translation coefficient and timevarying pre exponential factor,the zero order ageing dynamic model was modified,which combines the ageing kinetic model with the results of FDS.Finally,the evaluation method for the degree of polymerisation(DP)of silicone oil‐immersed paper was proposed,and experiments were conducted to obtain the parameters in the modified model and then to verify the proposed method.The results show that the proposed method can be used to evaluate the DP effectively.