The Gas Insulated Switchgears (GIS) used in high voltage transmission and distribution networks are reliable, compact, and maintenance-free. During the manufacturing process, some metal particles remain inside GIS which affects the breakdown strength of insulating gas and hence deteriorates the performance. The breakdown performance of R410A gas in the presence of free metal particles is presented in this paper. Iron and copper particles of various sizes and shapes are used in the research work. The impact of these free particles on the characteristic of R410A gas at various gas pressures and gap distances is elaborated. Power frequency breakdown voltage test in the presence of metal particles and selfrecoverability test are performed in a high voltage lab. The effect of various dimensions of metal particles on the dielectric strength of R410A gas under the quasi-uniform field in alternating current is examined. The impact on the breakdown voltage of R410A is analyzed by increasing the pressure and gap distance. Experimental results are discussed in the paper. As metal particles in between them can disrupt the R410A reaction barrier. According to the results of the experiments conducted, the breakdown voltage was affected by 30% by the addition of iron particles and 46.89% by the addition of copper particles, and it is concluded that iron particles perform better at different gaps distances.INDEX TERMS Gas insulated system, breakdown voltage, dielectric strength, metal particles, SF 6 gas I. INTRODUCTION