Audible Noise Calculation for Different Overhead Transmission Lines

Overhead lines are known to emit audible noise during foul weather conditions. Audible noise phenomena depend largely on the OHL conductor's surface gradient which is therefore also used in all equations for audible noise prediction. Various methods for the calculation of OHL surface gradients have been developed in the past. By using a realistic Indonesian tower design as an example, this contribution draws a comparison between surface gradient results obtained with several common calculation methods and with a finite element calculation. The investigated methods include the Maxwell Potential Coefficient Method, MARKT and MENGELE's method and Charge Simulation Method. A software has been developed for the assessment of the charge simulation method which is also presented here. The comparisons show that even relatively simple methods yield reliable results. Furthermore, this paper investigates the validity of audible noise prediction equations for AC as well as DC OHL with four-conductor bundles. For that purpose, audible noise measurements were carried out in a high voltage laboratory under realistic weather conditions. The results are used to calculate the corresponding sound power levels which are then compared to results calculated with the well-known BPA and EPRI equations for AC and DC audible noise prediction. The approach used to calculate the sound power levels of conductor bundles by measuring audible noise at fixed immission points is explained in great detail. The investigations show good agreement between laboratory results and AN predictions for AC OHL. However, some differences have been noted in the case of DC. In the last part of this contribution the compiled results are used to predict audible noise levels for a European AC line and for the planned HVDC-link between Sumatra and Java.