Dielectric properties of epoxy/paper composites in the different temperature environment

The main insulation material of the capacitance-graded bushing's capacitance core is composed of composites made from epoxy resin-impregnated paper (ERIP). The insulation property of ERIP composites is dependent on the fluctuations in environmental temperature. Therefore, the influences of a high-low temperature environment on the dielectric response properties of ERIP composites were studied in the paper. Firstly, the cycles test of ERIP samples is carried out in a high-low temperature environment from 20°C to 120°C, and ERIP samples are tested for frequency-domain dielectric spectroscopy (FDS) at each cycle. Then, the dielectric loss factor (tanδ) and the real and imaginary parts of complex capacitance at different cycle numbers and frequencies are all analyzed in the paper. Finally, the features are extracted from the frequency domain of tanδ, and the relationship between features and period is established. The test results and analysis indicated that as the number of cycles increases, the value of the tanδ and the imaginary part of the complex capacitance has an increasing trend, the value of the real part of the complex capacitor decreases with the increase of the number of cycles. As the number of cycles increases, the rate of change of the power tanδ, the imaginary and real parts of the power complex capacitance are 46.79%, 39.73%, and 4.26% respectively. The tanδ at 1Hz, 0.46Hz, and 0.22Hz are the selected features, all of which have a linear relationship with the cycle times. The conclusion can provide a data basis for the insulation state of the ERIP composites within the capacitance-graded bushing.