776 / 2022-03-31 21:54:01

Simulation of Transformer DC Bias Caused by Dynamic Stray Current

DC bias, dynamic stray current, simulation, magnetic circuit model

IEEE ICHVE 2022 / 1-PAGE ABSTRACT

Simulation of Transformer DC Bias Caused by Dynamic Stray Current

GONG Junqiang, CHEN Long, FANG Dachuan, WANG Kai,YU Guangyi,PAN Zhuohong

Southern Power Grid Shenzhen Power Supply Bureau Co

3334318660@qq.com,1071947368@qq.com,2195453908@qq.com,2994203234@qq.com,2500027872@qq.com,panzhuohong@ncepu.edu.cn

Purpose/Aim

With the continuous expansion of the operation scale of rail transit, the risk of DC bias of transformer caused by stray current invasion appears in urban power grid, which seriously affects the safe operation of urban power supply system. Therefore, it is necessary to carry out relevant tests and simulation analysis.

Experimental/Modeling methods

Based on the equivalent nonlinear magnetic circuit model, a method to deduce the no-load excitation current of transformer from the bias magnetic flux has been proposed, and the mapping relationship between the bias DC magnetic flux and the DC bias current is established by this method. Through the interpolation method and the operation of ordinary differential equation, a calculation method of transformer magnetic bias caused by dynamic stray current invasion has also been proposed.

Results/discussion

The calculation results show that under the action of dynamic stray current, the dc bias characteristics of the transformer also present dynamic changes. The biased magnetic flux varies with the stray current intruded by the transformer. Through the FFT analysis of the stray current in the field, we obtain that the highest frequency component of the stray current does not exceed 0.6 Hz. Furthermore, the influence of 0.6 Hz current on the transformer dc bias has been analyzed, and the results show that the magnetic bias characteristics will also show a slow change trend of 0.6 Hz.

Conclusions

In this paper, a risk assessment model of transformer dc bias caused by dynamic stray current has been proposed, and a case study has been carried out based on the measurement data of dynamic stray current. The results show that the dynamic characteristics of transformer DC bias are consistent with the dynamic characteristics of stray current.