420 / 2022-03-15 21:13:59

Research on interfacial charge evaluation method of oil paper insulation based on frequency domain dielectric response

界面电荷,频域介电,油纸绝缘

Research on interfacial charge evaluation method of oil paper insulation based on frequency domain dielectric response

Purpose/Aim

Due to the limitation of temporal and spatial resolution, the traditional PEA test method can only obtain the charge distribution in small-scale sample cannot measure the interface charge. A frequency domain dielectric response platform for oil-paper insulation with DC bias is built in this paper. In this paper, the effects of aging degree and moisture content on the interfacial charge accumulation under DC bias are quantitatively analyzed after considering temperature. Finally, a method for calculating the interfacial charge of oil paper insulation based on the dielectric response in frequency domain is proposed. All these have certain reference value to explore the quantitative evaluation of the oil paper interface charge under strong DC component.

Experimental/Modeling methods

The paper constructs the equivalent insulation structure of paper-oil-paper. And accelerated thermal aging test and moisture absorption test were carried out on oil-paper insulation samples. Then, the aging and damp samples were tested for FDS under DC bias at different temperatures. After the test is complete, paper used the transfer function to eliminate the influence of isolating capacitance and protection resistance on test results. Finally, based on Maxwell-Wagner theory and frequency domain dielectric response test data, the quantitative characterization of the interfacial charge of oil paper insulation was achieved.

Results/discussion

Compared with no DC bias voltage, aging and damp oiled paper models under DC bias voltage, the loss factor curve decreases slightly in high frequency band and obviously in middle frequency and low frequency band. And this phenomenon becomes more obvious with the increase of test temperature.

Conclusions

Through the test platform built in this paper, and combined with the transfer function to get the test curves. The paper uses the curves to quantitatively characterize the interfacial charge accumulation of oil-paper insulation aging and moisture exposure. At the same time, according to the analysis of the test results, the increase of moisture content will make it easier to inject positive and negative charges in the oil paper samples, and the increase of the number of small molecules in the cellulose molecules after the aging of the paper make the interfacial charge accumulation more significant.