Algorithm for Solving Trip-Out Rate Due to Shielding Failure of Bent Transmission Line

摘要

Accurate assessment of lightning protection performance of extra high voltage transmission lines is important for transmission line design and different lightning protection. Based on the electro-geometrical model, this paper introduces the angle influence factor, and presents an algorithm for shielding failure trip-out rate of angle tower, and the existing algorithm is expanded. By establishing the three-dimensional geometric model of the angle tower, the electrical geometric relations of conductors and ground wires on both sides are analyzed, respectively, and the projection area algorithm for shielding failure is modified. To further verify the application value of the calculation algorithm, the change of the shielding failure trip-out rate of the typical angle tower with the bending angle of transmission line and the tower height in a 500 kV transmission line is analyzed. The analysis results show that the trip-out rate of the outside corner is higher than that of the inside one, and with the increase of the angle and the height of the tower, the trip-out rate shows an upward trend. When the tension tower height is 71.5 m and the angle increases from 0° to 80°, the outside shielding failure trip-out rate increased by 10.9% and the inside decreased by 9.3%. Compared with the classical electro-geometrical model calculation, the difference of trip-out rate is 4.3% when the bending angle is 80°. When the tangent tower height is 70m and the angle increases from 0° to 40°, the shielding failure trip-out rate on the outside increased by 5.9% while the inside decreased by 6.2%. The research results provide a simple algorithm for solving bending transmission line and give some reference for lightning protection design of EHV transmission lines.