In this research, the leakage current (LC) and applied voltage waveforms on samples of installed outdoor porcelain and silicone rubber (SIR) insulators were measured by using a storage digital oscilloscope concurrent with humidity, temperature, and illuminance measurements. Essentially, the measurements were conducted daily, every three hours, for thirty days, and the data were analyzed using exponential regressions, box plots, and correlation coefficients. The porcelain and SIR insulator leakage currents varied from 23.7 A to 28.8 A and 8.4 A to 10.35 A for median values, respectively, while for outlier excluded values, they varied from 20.3 A to 40.0 A and 5.1 A to 17.1 A, respectively. Both leakage currents slightly increased as the exposure duration of the insulator rose, while the ratio decreased very slightly. Additionally, the leakage currents decreased moderately and slightly as the temperature and illuminance increased, respectively. However, the parabolic leakage currents increased as the humidity rose, especially at high humidity. Therefore, the porcelain insulator was more susceptible than the daily SIR, while the SIR insulator was more highly influenced by aging of the exposure duration. The rainy condition contributed to the highest leakage currents on both insulators, whereas the drizzle condition contributed to the highest leakage current on the SIR insulator. The total harmonic distortion (THD) and phase angle of the porcelain insulator leakage currents experienced differences of 5.8% and 7.8 degrees in the minimum and maximum humidity, respectively, but both quantities were less for the SIR insulator. INDEX TERMS humidity, leakage current, porcelain, silicone rubber I. INTRODUCTION High voltage outdoor insulators have an important role in electrical power transmission and distribution systems, including operational reliability, safety, and efficiency [1]. However, their functions are mostly influenced by environmental conditions [2-3]. Common insulator materials include glass and porcelain, which are ceramic materials that have been used for hundreds of years. Moreover, composite and cast cycloaliphatic epoxy resin (epoxy resin, ER), as a polymeric category, has been used in the last few decades [3-4]. These insulators have sheds for reducing the electric field stress and tolerating the accumulation of pollution [5]. Currently, research conducted on insulator leakage currents based on daily time functions is limited. Vosloo et al. [6] illustrated the average peak leakage currents on some insulators, and Roman et al. [7] monitored the insitu dc leakage current magnitudes, namely, rain, humidity, and temperature, on composite and glass insulators. According to Castillo-Sierra et al. [8], the ceramic insulator leakage currents were measured using a clamp meter, as were the temperature and humidity, followed by a regression analysis. Further research by Vosloo and Holtzhausen [9] showed that the peak leakage current of porcelain insulators, including precipitation, relative humidity (RH), ul...
