Kinerja isolator polimer silicone rubber menurun apabila digunakan didaerah berpolutan tinggi. Untuk mengatasi kelemahan tersebut pemakaian bahan pengisi seperti fly ash bertujuan untuk memperbaiki kinerja serta menekan biaya pembuatan dari isolator polimer. Penelitian ini bertujuan untuk mengetahui kinerja isolator polimer silicone rubber berbahan pengisi fly ash batu bara, dimana parameter yang diamati yaitu arus bocor, serta mencari nilai optimasi pencampuran isolator polimer silicone rubber berbahan pengisi fly ash batu bara dengan komposisi 0%-80%. Metode untuk mengetahui adanya pengaruh kabut garam terhadap arus bocor pada isolator yaitu dengan memberikan kontaminan kabut garam pada isolator uji secara terus-menerus selama 60 detik, data hasil uji dilihat pada alat Sonel PQM-707 yang merupakan alat untuk mengukur arus bocor pada isolator. Hasil pengujian menunjukkan nilai arus bocor isolator polimer silicone rubber berbahan pengisi fly ash semakin menurun seiring dengan penambahan komposisi fly ash, namun penambahan fly ash yang berlebih dapat meningkatkan nilai arus bocor. Pada isolator berbahan pengisi fly ash batubara Pabrik Semen Bosowa Lombok sebelum diberi kabut garam nilai optimasi yang didapat 44,04% sedangkan saat diberi kabut garam 50,88%. Pada isolator berbahan pengisi fly ash batubara Pabrik SBI Bekasi sebelum diberi kabut garam didapat nilai optimasi 40,63% sedangkan saat diberi kabut garam didapat 53,69%.

The performance of silicone polymer rubber insulators decreases when used in high-pollution areas. To overcome weaknesses, the use of filler materials such as fly ash aims to improve performance and reduce manufacturing costs of polymer insulators. This research aims to determine the performance of silicone rubber polymer insulators made from coal fly ash filler, where the parameters observed are leakage current, and to find the optimization value of mixing silicone rubber polymer insulators made from coal fly ash filler with a composition of 0% -80%. The method to determine the influence of salt mist on leakage currents in insulators is by applying salt mist contaminants to the test insulator continuously for 60 seconds. The test result data is viewed on the Sonel PQM-707 tool which is a tool for measuring leakage currents in insulators. The test results show that the leakage current value of silicone rubber polymer insulators made from fly ash filler decreases along with the addition of fly ash composition, but the addition of excess fly ash can increase the leakage current value. In insulators made from coal fly ash filler at the Bosowa Lombok Cement Factory before being treated with salt mist, the optimization value obtained was 44.04%, whereas when treated with salt mist it was 50.88%. In insulators made from coal fly ash filler at the SBI Bekasi Factory, before being given salt mist, the optimization value was 40.63%, whereas when given salt mist the optimization value was 53.69%.