The Evaluation of Daily Comparative Leakage Currents on Porcelain and Silicone Rubber Insulators Under Natural Environmental Conditions

Abstract

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 $23.7~\mu \text{A}$ to $28.8~\mu \text{A}$ and $8.4~\mu \text{A}$ to $10.35~\mu \text{A}$ for median values, respectively, while for outlier excluded values, they varied from $20.3~\mu \text{A}$ to $40.0~\mu \text{A}$ and $5.1~\mu \text{A}$ to $17.1~\mu \text{A}$ , 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.