Lightning-shielding Design Of A Transmission Line

Lightning is a natural phenomenon. The harm of lightning on power equipment, especially on a transmission line, is analyzed in this thesis. By the lightning-shielding design of a transmission line, some issues are investigated in detail. These issues include how to improve the lightning-shielding level of a transmission line, how to lower effectively the lightning trip-out rate of a transmission line, and how to decrease the impact of lightning on the safe operation of a power grid.The principle of lightning discharge to a transmission line is described in this thesis. The forming and developing processes of lightning are introduced. Also introduced are the forming and developing processes of lightning voltage and lightning current, as well as the discharge principle under the breakdown of an insulator. The main calculation methods of the lightning parameters, the lightning-resistance level, the lightning trip-out rate, the inducing lightning and the direct striking lightning are put forward.Several practical ways of lightning-shielding design of a transmission line in our country are analyzed. These ways include the reasonable choice of right-of-way of a transmission line, the rational design of lightning conductors, the lowering of tower's grounding resistance, the installation of lightning arresters, the installation of coupling lightning conductors, and the improving of line insulation level, and so forth. Some of them are analyzed in detail and studied quantitatively. A special lightning-shielding design method for special right-of-way is also given in this thesis. It is pointed out that the power supply reliability may be improved by neutral point's non-solid-grounding, standby power supply automatic switching, reclose equipment, and so forth.Using the common and practical methods for lightning-shielding design of a transmission line, the lightning shielding of 110kV Shihua (Shitan substation to Huashi substation) line is analyzed in detail and then designed. The actuality of the local electric grid is taken into considered in the design. Also considered are the local climate, topography, environment, and other factors. The best lightning-shielding scheme for the transmission line is proposed. The situations of construction, operation and lightning-shielding of the HOkV Shihua transmission line are introduced. The issue of improving lightning-shielding level of a transmission line is investigated from the operation point of view.