Because of the aforementioned appeal of the regression trees technique, itwill be used to investigate the behavior of EPDM composite insulators againstthe SiR contents based on the recorded experimental work. The percentage SiRcontents in EPDM composites are 0, 25, 75 and 100% respectively. Generally, theEPDM composite polymer insulator properties are enhanced with increasing theSiR contents percentage as shown in Figs 17 to 19. Fig.
19 shows the effect of water droplet number upon the EPDM behavior with fixedwater droplets volume and conductivity. Increasing the number of droplets decreases the flashover voltage at thesame droplet size and water conductivity. For instance, at 1, 3, 5 droplets, the flashover voltages are 19, 17, 16kVand 11, 9.99, 8kV for 100% and 50% SiR contents with constant water conductivityand droplets volume.
Fig. 20 shows the effect of water size upon the flashover voltage. The dropletsvolumes are 0.
01, 0.1, and 0.15ml respectively. The larger the droplets volumeis, the lower the flashover voltage is obtained.
For constant water conductivity,it is noted that the impact of the droplet volume appears clearly and stronglyfor one droplet. However, the increase of droplets volume from 0.1 to 0.15mlhas less impact on the flashover voltage at 3 and 5 droplets. For instance, at100% SiR, the flashover voltages record 19, 17, 15kV respectively for onedroplet at volumes of 0.05, 0.1, 0.15ml respectively.
The corresponding datafor 3 and 5 droplets are 17, 14, 13kV and 16, 11, 10kV respectively with 1kVdifference. Fig. 21 illustrates the relationship between the flashover voltages and SiRcontents in EPDM at various water conductivities with three droplets. Thetested water conductivities are 50, 500, and 1000?S/cm. For 100% SiR contents, 0.1mlwater droplet volume, and 3 droplets, the flashover voltages record 14, 12,10kV at 50, 500, and 1000?S/cm.
For constant droplets number and volume, it can be noticed that as the droplet waterconductivity increases, the EPDM flashover voltage decreases. It can be concluded fromthe prediction values in Figs. 19 to 21 that the hydrophobic surfaces ofEPDM composites polymer insulators were pronounced impact on the values offlashover voltages. The electrical properties of EPDM composite insulators wereimproved with increasing the silicon rubber contents. At wet conditions weather with high salinity(i.e.
low conductivity), the hydrophobic surface of EPDM composite insulatorwithstands more flashover voltages.