## 7 Conclusions  
In this paper, a multi-physical field coupling finite element analysis model of converter transformer and gas relay is established by COMSOL 6.0 simulation software, and the deflection and oil flow characteristics of the internal baffle of gas relay under the action of magnetizing inrush current are analyzed. The following conclusions have been obtained:  
(1) By studying the oil flow characteristics at the gas relay under the inrush current, it is known that under the inrush current excitation, the insulating oil rushes into the oil pipe from the case, and at this time, the insulating oil impacts the baffle plate. When the rate of insulating oil is too large, the baffle deflection reaches the threshold value, causing the gas relay to trip. And the insulating oil flow rate through the gas relay reaches the peak value at 0.6 ms, and then the oil flow rate decays and gradually decreases. (2) Under the action of the inrush current of 0\({}^{\circ}\) closing angle and 0.8 pu residual magnetization, the insulating oil flowing into the gas relay will impact the baffle plate, and the baffle plate of the gas relay will start to deflect at 4 ms. At 4 ms, the baffle starts to deflect. Before the flow rate into the gas relay reaches the peak value, i.e., from 4 ms to 6 ms, the deflection of the baffle increases with the increase in the flow rate of the input insulating oil. After 6 ms, the flow rate of the insulating oil into the gas relay decays, and the impact of the insulating oil causes the baffle to continue to deflect, but the speed of  
Figure 18: Deflection angle of gas relay baffle for multiple cycles under different operating conditions. deflection of the baffle decreases slowly. At 9 ms, the deflection angle of the baffle plate of the gas relay reaches the maximum value of the baffle plate rotation; at this time, the baffle plate is connected with the reed switch, which causes the gas relay to trip. (3) Mathematical fitting is used to obtain the functional relationship between the gas relay baffle plate and the amplitude under different working conditions, and this relationship is verified. The fitting results are within 3\({}^{\circ}\) of the actual experimental results, and the fitting results show that when the inrush current generated by the converter transformer reaches a magnitude of 6.37 kA, the gas relay has the risk of tripping. (4) The deflection of the gas relay under various inrush current conditions is analyzed. It is concluded that the greater the inrush current amplitude, the shorter the time for the deflection of the baffle to reach the peak value, and the greater the change of the deflection of the baffle in the excitation of multiple cycles. Finally, in order to reduce the risk of gas relay misoperation caused by inrush current, the following suggestions are put forward: (1) access the closing resistance that can limit the inrush current when the converter transformer is closing; (2) by controlling the closing phase, the inrush current amplitude is reduced; (3) effective demagnetization measures are adopted to reduce the residual magnetism inside the core. In this paper, the deflection and oil flow characteristics of the baffle of the gas relay are investigated by using the finite element method, and the subsequent research needs to consider the effect of the vibration of the gas relay on the baffle deflection, and to conduct vibration table experiments to study the intrinsic frequency of the baffle of the gas relay, so as to lay the foundation for the formation of the multi-information method of the state assessment of the gas relay. Conceptualization, W.H. and Z.Z. ; methodology, Z.Z. and J.D. ; software, W.H. ; validation, W.H. ; formal analysis, W.H. and Z.Z. ; investigation, W.H. ; resources, Y.Y. ; data curation, W.H. ; writing--original draft preparation, W.H. ; writing--review and editing, Y.Y., J.G. and X.P. ; visualization, W.H. ; supervision, Z.Z., J.D. and Z.P. ; project administration, J.L. and H.Y. ; funding acquisition, J.L.