**7. Conclusions**

A new method to suppress VFTO was proposed, called a damping busbar. The mechanism of this new method was analyzed. A calculation method for the self-inductance of the damping busbar at high frequency was presented. Moreover, the inductance effect of the damping busbar on VFTO suppression was studied as well. As a result, the amplitude of the VFTO was reduced by approximately 27% after applying the damping busbar. A further enhancement of the suppression effect was investigated by designing a spiral litz coil connected in series with the busbar, which increased the total inductance value. Consequently, a good damping effect was achieved by utilizing the inductive and resistance arrangemen<sup>t</sup> which was formed by the improved design of the spiral tube damping busbar. The conclusions are as follows.


However, research on improving the proposed design to increase the equivalent inductance value by increasing the length of the busbar and the number of turns has to be considered. Many different adaptations, tests, and experiments should be investigated in future work (i.e., experimental study of a 1000 kV GIS station VFTO after installing the improved damping busbar).

**Author Contributions:** Conceptualization, R.A.A., Y.-X.S., and W.X.; formal analysis, R.A.A.; investigation, R.A.A., Y.-X.S., and W.X.; writing—original draft preparation, R.A.A. and W.X.; supervision, Y.-X.S., and W.X.

**Conflicts of Interest:** The authors declare no conflict of interest.
