Over-voltage protector for overhead insulated distribution lines

A new type over voltage protector that combining forward against lightning technique of discharge controllable lightning needle with nonlinear technique of ZnO surge arrester together for restraining over voltage had been designed in this paper. This protector was named discharge controllable over voltage protector and had been used for protecting overhead insulated lines from line melted down and line switch off. Its protecting principle is based on disemboguement theory of air-discharge and nonlinear V-A character of current limit unit. The overhead lines may operate more safely and more reliably when the protector installed on. In the paper, lightning impulse test and V-s character test of lightning impulse were applied to confirm the length of gap in series and optimize proper insulation level as well as technical parameters of the protector. The test research results proved that the discharge controllable over voltage protector is not only effectively prevent overhead line from lightning shielding failure, but also effectively prevent overhead line from melted down and switch off faults caused by any reason. Its capability of forward lightning protection and shutting off power frequency current as well as restraining over voltage is more effectively, more reliably and more safely.