In order to meet the requirements of corrosion resistance of the grounding material and thermal stability of the grounding material of the transmission line towers, under the condition of power frequency current and high-frequency lightning current scattering into the ground in the case of short-circuit fault and lightning strikes, a kind of high-current capability flexible graphite grounding material was developed. The corrosion resistance of the flexible graphite grounding material and the steel type grounding material was compared by the soil simulation solution corrosion tests. The contact performance with different soils of the two materials was analyzed by the actual contact resistance measurement test. The thermal stability and the impulse current effective length of this grounding material were studied by means of simulation calculation. The results show that the high-current capability flexible graphite grounding material has a strong anticorrosion characteristic, whose reliable service life can exceed 30 years. Compared to the round steel grounding material, the contact resistance with the soil can be reduced by approximately 30%, and the impulse current effective length can be increased by about 30%. INDEX TERMS Flexible graphite grounding material, corrosion resistant characteristic, contact resistance, thermal stability, impulse current effective length.

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Series multi‐break mechanical switch is one of the critical components of high‐voltage hybrid DC circuit breakers. However, due to the existence of distributed capacitance, the voltage distribution between the breaks is not balanced. This paper proposed a voltage sharing configuration method of the mechanical switch of hybrid DC circuit breaker, and carried out the static DC voltage and the transient voltage distribution characteristics tests to verify its effectiveness. Considering the influence of whole structure of the circuit breaker, this paper established the electrostatic field model and circuit simulation model of a typical ±535‐kV hybrid DC circuit breaker. And it analyzed the influence of single break's opening fault, breaking open distance, and the shielding fitting on the voltage distribution characteristics of series six break mechanical switch. According to the simulation results based on the Zhangbei voltage source converter‐based high‐voltage direct current project type test parameters, the parameters design of the voltage sharing components of the mechanical switch are obtained, which can meet the voltage sharing coefficient requirement of 95%.