Calculation and Research of Audible Noise of AC Transmission Lines (Ⅱ) - Distribution Under Crossing Erection

When transmission lines are erected in a crossing way, the audible noise distribution characteristics are the key factors in the design of the lines. We adopted the sound power level prediction formula proposed by China Electric Power Research Institute to build an audible noise calculation model under crossing erection in which the effect of sagging is taken into consideration; meanwhile the coupling of surface electric field strength between two lines is also taken into consideration in the model. Firstly, this model was used to calculate the audible noise distribution characteristics of an actual ultra-high-voltage 1 000 kV line crossing an extra-high-voltage 500 kV line in a crossing area under good weather conditions. The audible noise distribution and actual measurement results on three typical paths were compared and analyzed. The results show that the average relative error on the three paths is 3.09%, which verifies the accuracy of the calculation model in this paper. Furthermore, the effects of the crossing angle, 500 kV phase sequence arrangement, and the air gap distance between two lines on the audible noise distribution in the crossing area were investigated when a single-circuit line of 1 000 kV and a double-circuit line of 500 kV were crossed. The results show that when the cross angle changes from 0° to 90°, the audible noise at the 20 m away from the edge gradually decreases as the crossover angle increases, and the audible noise amplitude increases first and then decreases slowly. The trend is that when the crossing angle is 45°, the amplitude of the audible noise is the largest; the ABC-ABC on the 500 kV double-circuit line is adopted to optimize the audible noise distribution in the crossing area; with the increase of the air gap distance, the audible noise level of the 1 000 kV line increases as a whole. © 2019, High Voltage Engineering Editorial Department of CEPRI. All right reserved.