The AC-behavior of a hydrophilic and hydrophobic post insulator during rain

The AC-behavior of a hydrophilic and a hydrophobic porcelain post insulator is studied during four different rain conditions by measuring the electric field distribution, resistive and capacitive leakage currents and UV-photography of the discharge activity. The results are in agreement with each other and show resistive field distributions along the hydrophilic insulator at the normal operating voltage level. Electric field measurements reveal the deterioration in time of the surface hydrophobicity. Leakage current measurements are difficult to relate to electric field distributions, while electric field measurements and UV-photography are powerful tools to determine the condition of the insulator