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Standards for Insulating links
ANSI/CPLSO-14
ANSI/UL2737 (Withdrawn)
ASTM F2973
MIL-L-24410 (Withdrawn)
Tests by Independent Organizations
Load Insulator
Miller & Hirtzer
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388 As an example, if flashover occurred in 12 out of 25, the probability is 12/25=0.48. This test method simulates actual operating conditions of an insulating link and gives flashover probability curves for short duration voltage applications. In addition, standard contaminated flashover voltage of Link 3 was measured by using the IEC Standard 507. The flashover voltage of Link 2 and 3 were calculated [13]. Test results The major technical data points of the tested insulator links are summarized in Table 3. Table 3. Technical data of the tested links. Flashover probability of links with light contamination (ESDD = 0.03 mg/cm2) is shown in Figure 4. These curves indicate significant differences in the link's performance. The critical factor is leakage distance. Flashover voltage increases with leakage distance. Link 1 has a smooth body without corrugation and the shortest leakage disrance. Link 2 has a longer leakage distance and better performance. The new link, with twice as long leakage distance has the best pelf0lTEUlCe. The spread between the withstand voltage (2%) and flashover voltage (98%) is between 1542% of the withstand voltage. h .$? -1 - 0. n * c .- - Q $ 0. L n. 0. 0 0. L a, z d= UI Q i; 0. 25 30 35 40 45 50 55 Voltage (kV) Figure 4. Flashover probability of insulator links with light contamination (0.03 mg/cm2) and 1 sec energization. 40 45 50 55 Voltage (kV) Figure 5. Flashover probability of Link 3 at different pollution level and 1 second energization. Figure 5 shows the effect of contamination severity on the flashover probability. Increasing contamination decreases flashover voltage. The flashover voltage (98%) decreased more than the withstand voltage (2%). The flashover voltage of Link 3 was also measured by the standard up and down method at 0.03, 0.1 and 0.3 pollution levels E121. In this case, the insulators are energized with a nearly constant voltage. The results also show that the flashover voltage decreases by increasing the pollution. Flashover voltage measured with the "up and down" method is marked by a dot on Figure 5 for comparison. It can be seen that the flashover voltage obtained with constant energization correspnds to the 7585% flashover probability with one second energization. 1 .o eR U ' 0.4 L QI L 0 .o 41 42 43 44 45 46 47 48 49 50 Voltage (kV) Figure 6. Effect of energization time. Link 3, heavy pollution, 1 sec and 10 sec energization.
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