© 2020 Turkish Chambers of Electrical Engineers.This paper presents inclined plane tests for high temperature vulcanized (HTV) silicone rubber samples incorporated with 50% aluminum trihydrate (ATH) by weight. Five identical test samples were used in the experimental study. The correlations between the maximum temperature on the silicone sample surfaces and the harmonic components of the leakage currents and powers were investigated. 3.5 kVrms constant AC test voltage was considered for the inclined plane test. LabVIEW data acquisition system was used to record and monitor the leakage current data, and FLIR IR thermal camera was utilized to take temperature data. The results showed that a high degree of correlations was found not only among the 3rd harmonic components currents / powers of the leakage currents and the maximum temperatures, but also among 5th and 7th harmonic components of currents / powers and the temperatures.