Research On Lightning Shielding Failure Performance And Lightning Protection Measures Of UHV AC Transmission Lines

The advantage of having long transmission distance, large sending capacity, low lineloss, saving construction investment, reducing the area of land using etc, Ultra highvoltage(UHV) power grid is particular important for the optimal allocation of power resourcesand the national economy, however, the particularity of its own determines the operationprocess is often accompanied by all sorts of problems. In this paper, overvoltage problem andelectric field environment around UHV transmission lines were analyzed emphatically.Operational experience indicates: The main reason of lightning trip failure on UHValternating current transmission line caused by lightning shielding failure on the conductors.The improved electric geometry model(EGM) was used to make a qualitative analysis thelightning shielding failure performance of transmission line with the different lightningcurrent amplitude, terrains and topographic features, overhead ground wire protection angleand work voltage on conductor, what’s more, also described the impact of lightning shieldingfailure by the line insulation level and ground vegetation in this paper. Then, the general rulesof the lightning shielding failure performance were summarized under each factor. Given Amulti-conductor impulse corona model, which not only takes both the corona effect ofoverhead ground wire and the coupling between the transmission lines with corona intoconsideration, but also considers the distribution characteristic of the corona capacitancebetween the transmission and ground, to compensate for the EGM cannot reflect the lightningovervoltage wave propagation process on the conductor when shielding failure, in this article.In addition, a lightning shielding failure simulation model of UHVAC transmission lines wasestablished by using electromagnetic transient calculation software ATP-EMTP. Got thecharacteristics of the lightning overvoltage wave propagation process after took account of theimpulse corona effect of the transmission lines. More over, using the finite element analysissoftware ANSYS calculated the electrical field environment near the UHV Single-circuit ACtransmission line corridors when the normal operation of the lines, as well as under thenormal and lightning discharge operation circumstances the distribution of the surface electricfield intensity of the transmission line was calculated. The result show that, the electrical fieldenvironment near the UHV Single-circuit AC transmission line corridors comply with thenational standards limits requirement, lightning discharge has a great influent on thedistribution of the surface electric field intensity of the overhead ground wire, however, it hasa limited effect on the conductor, so the overhead ground wires very easy produce the upwardleader. Finally, this paper giving the differentiated lightning protection comprehensive governance measures of the UHV Single-circuit AC transmission line based on the aboveanalysis calculation. Differentiated lightning protection comprehensive governance measuresof combine “mediator-type” lightning protection and “plus-type” lightning protection shouldbe taken adjust measures to local conditions. To carry out pertinently differentiation lightningshielding failure prevention work, focus on strengthening the protection strategy of importantlines and multi lightning and strong lightning area and easy shielding failure flashover of lines,to improve the overall technical and economy of lightning protection.