抄録
Installation of insulated wires in a high voltage overhead distribution system has decreased electric shock accidents, but on the other hand the ocurrence of wire melting accidents due to induced lightning surge has raised another problem. As flashover due to lightning surge takes place over the surface of insulator, leader strokes progress from the tip of the binding wire along the surface of the insulated wire. Clarifying the characteristics of these leader strokes will conceivably contribute to the prevention of wire melting accidents.
Numerous experiments concerning these leader strokes were carried out, which resulted in clarification of several noticeable characteristics.
From the results of this paper the following matters are clarified.
(1) The progression speed of the leader strokes from the tip of the binding wire to the distance of approx. 20 cm along the surface of the insulated wire becomes faster with increasing gap (B G) length.
(2) The potential of the tip of leader stroke against ground increases monotonously with the progression length, i. e. the distance from the tip of the binding wire. In addition, within the range of about 60 cm from the tip of the binding wire, the rate of voltage drop is approx. 250 V/cm.
(3) The results of the measurement of the potential of the leader stroke tips against conductors at the moment of progression halt (progression halt voltage) carried out with respect to three sorts of insulated wires show that the progression halt voltage is dependent to sheath thickness and dielectric constant, and takes a constant value inherent to the insulated wire.
