## 6 Conclusions  
HVB-LA-DLTL systems are complex coupling systems. The coupling effect between the HV bushings, lightning arresters, and DLTL under seismic loadings has a great influence on the force applied on the HV bushings and lightning arresters. However, the existing studies do not consider the adverse impacts of coupling vibrations on HV bushings and lightning arresters in whole systems under seismic loadings.  
This paper analyzes the bearing performance of a certain high-voltage casing lead structure system and single structure electrical equipment under seismic loads. El Centro waves, Taft waves, and artificial standard time-history waves were selected for one-way and three-way input tests. The PGA is obtained from the response of the structure under six working conditions: 0.035, 0.1, 0.22, 0.07, 0.2, and 0.4 g. The following conclusions are drawn regarding the load-bearing performance:  
(1) Under the action of earthquake loading, the down conductor of the upper part of the structural system has a very strong adverse effect on the lower electrical equipment. As the seismic intensity increases, the structural displacement increases, and a lack of redundancy of the down conductor causes the high-voltage casing and the arrester to pull against each other and quickly amplifies their respective dynamic responses in a nonlinear form;  
(2) The down conductor has a greater impact on the high-voltage casing than on the arrester. When the structure is under the influence of the PGA = 0.4 g earthquake, the maximum stress at the root of the high-voltage casing in the system increases by approximately 13.02% compared to that of the single body. The maximum stress at the root of the arrester increases by approximately 7.80%. The down line has a considerably greater effect on the magnification of the structure in the X-direction than in the Z-direction. Sufficient redundancy during the design of the down conductor is recommended;  
(3) When the PGA is 0.4 g, the safety factor of the root stress of the high-voltage casing under horizontal input is less than the 1.67 specification required by the standard GB50260-2013. According to the particular features of the high-voltage casing lead system and local seismic fortification requirements, the adoption of appropriate dampers and other shock-absorbing equipment are recommended;  
(4) In response to the application of one-way and three-way seismic inputs in the X- and Z-directions, the most vulnerable location in the structure under earthquake action is at the root of the high-pressure casing. Comparing the three-way and the one-way inputs shows that the response of the structure greatly increases under three-way input, and the structure deforms substantially. In the design process, three-way and one-way inputs should be calculated separately for envelope design.  
Conceptualization, M.Z. and G.Z.; methodology, M.Z. and R.W.; software, M.Z. and G.Z.; validation, R.W., Y.D. and G.Z.; formal analysis, R.W. and Y.D.; investigation, R.W.  
Figure 23: Displacement amplification under different seismic waves.  
and Y.D.; resources, M.Z. and G.Z.; data curation, R.W.; writing--original draft preparation, M.Z. and R.W.; writing--review and editing, Y.D. and G.Z. All authors have read and agreed to the published version of the manuscript.  
This research was funded by the National Natural Science Foundation of China (Grant no. 51578512) and the Cultivating Fund Project for Young Teachers of Zhengzhou University (Grant no. JC21539028).  
Not applicable.  
Data Availability Statement: Data are contained within this article.  
The authors declare no conflict of interest.