Optimization of Audible Noise Levels in an AC/DC Hybrid Transmission Line

In this paper, the Audible Noise (AN) levels generated by corona in an AC/DC hybrid transmission line are computed by means of a method proposed by CIGRE. The method consists of two sections: firstly, the electric field at the surface of the conductors is calculated contemplating the coupling between AC and DC circuits. Secondly, the AN profiles caused by the hybrid line are obtained through empirical formulas under rain and fair weather conditions. The study case consists in the determination of the Audible Noise levels of a hybrid transmission line. The voltage of the AC circuit is 345 kV while for the DC circuit is ±380 kV. Two geometric configurations are analyzed. Afterwards, an optimization study is carried out to minimize the maximum noise values, considering as decision variables the conductors radius, the number of conductors, and the bundle spacing. At the end, nominal and optimized Audible Noise profiles are compared.