94 / 2021-06-05 14:31:36

FREQUENCY DOMAIN SPECTRUM CORRECTION METHOD IN OIL-PAPER INSULATION AT TIME-VARYING TEMPERATURE

Frequency domain spectroscopy (FDS) is one of the most important methods to evaluate the insulation status of the capacitive oil-paper bushing. However, the existing evaluation methods are all based on the FDS curves under the steady-state temperature, and the actual test temperature of the equipment is often dynamic, which will affect the accuracy of the evaluation model. In this paper, the digital twin (DT) technology was used to build the simulation model of the bushing, and the temperature change process of the bushing after power failure was studied by considering three kinds of heat dissipation conditions: convective heat dissipation, radiation heat dissipation and conduction heat dissipation. At the same time, the Biharmonic interpolation method was selected to construct the three-dimensional non-linear mapping relationship of FDS test frequency, test temperature and reference temperature, which can better realize the correction of FDS curves under transient temperature. Finally, the FDS curves of the bushing under time-varying temperature was obtained by simulating the heat dissipation process through experiments. According to the heat dissipation curves of the bushing obtained by the simulation model and the Biharmonic interpolation method, the curves were calibrated to the specified reference temperature, which verified the accuracy of the model.