Transmission Line Insulator Lightning Flashover Characteristics

Lightning poses a great threat to overhead transmission lines. Lightning stroke fault may cause power interruption and over-voltage due to lightning stroke may do harm to electronic apparatus. Researchers of home and abroad have studied the principles of lightning activity, physical mechanism of lightning stroke at lines and flashover or breakdown of insulation under impulse voltage. The relatively sophisticate theory system was established. Some lightning parameters may be acquired by LLS. Direct stroke rate and pole stroke rate may be obtained through Lightning shielding modeling. The lightning propagation analysis in towers and conductors can get lightning electro-magnetic transient result.Major influencing factors of lightning properties of insulators are analyzed and summarized as well as some valuable conclusions are presented in the thesis. Lightning properties of varied suspension types of line insulators were not well known and hamper the applications. Tests of lightning flashover characteristics of parallel and V-shape of insulators are carried out in the thesis, and may provide instruction to installation of insulators. Grading ring is originally applied to reduce non-uniformity of electrical intensity though they may cause the decrease of insulation distances. Electrode semiconductor and insulating coating method is experimented in the thesis in order to improve breakdown voltages. In the thesis, the preliminary theory analysis about the influence of coating on the impulse breakdown property is conducted. Relatively long distance air breakdown is classified to stream discharge theory, which air ionization holds the prominent places. In contrast, the improvement to the electrical field distortion and obstacle to electron injection may have little effect.Finite element calculation software is utilised to electrical field, It shows that insulator suspension type may cause change of electrical field, thus influence air breakdown voltage, The decrease of gap distance between parallel suspension insulators can increase electrical field intensity and make air breakdown easy to occur.