ON THE IMPULSE WET FLASH-OVER VOLTAGE OF SUSPENSION INSULATORS (REPORT IV)

The experiments performed by the author of this paper: (1)A.C. dry flash-over test was performed，under the conditions somewhat different from the conventional ones，both on a suspension insulator in normal conditions and that with some broken porcelain parts. -Report I-(October 1959) (2)A.C. dry flash-over test was performed on two suspension insulators with greatly damaged porcelain parts. -Report II-(November 1959) (3)Impulse voltage was applied experimentally to one suspension insulator in normal conditions and two insulators with some broken parts. -Report III-(October, 1963) The material used in the experiment reported in the present paper was the same of those used in the test (3) above，where the testing condition was different from that of the foregolng tests in the point that the insulator was fully soaked in the water before it was applied the voltage. The result obtained in this occasion was that the falling ratio of the flash-over voltage read (was observed to be) 10-12%，which indicated that a neat clean surface of the insulator even wet with water did not result in so great a falling of the voltage, though influenced by the humidity of the atmospere as usual in this case. In the observation，which had been kept on since the time of Report I, of distributions of the discharging directions，the discharging route was observed not always gathering along the short-cut distances. The causes and other aspects of this phenomenon are left to be studied further