Research on impulse discharge characteristics of parallel gap

With parallel gap, by controlling the motion path of the electric arc, effectively avoid burning and damaging the insulator during lightning strike so that its importance in measures of lightning protection for transmitting line is continually improved. Initial discharge position is key consideration during design of parallel gap and depends on discharge characteristics of parallel gap under the action of lightning surge when the lightning strikes the tower or line. This paper gives three types of parallel gap used to protect the composite insulator, sets up the impulse discharge test and observation platform including high-speed camera, studies the impulse discharge characteristics of parallel gap and analyzes the influence of structural parameters on the discharge characteristics. This study showed that there is randomness for discharge path of parallel gap; three types of parallel gap given in this paper can achieve 100% discharge rate of parallel gap; the determinant of discharge rate in the presupposition discharge area (PDA) is the distance that the presupposition discharge area stands out of the whole electrode plane. When this distance exceeds 20mm or more, it can ensure that most of the discharge occurs in the PDA; the parallel gap can reduce the insulation distance of 4000mm insulator about 40mm, U₅₀ about 1%, which may approximately consider that the parallel gap has no influence on the insulating property of the insulator.