Acoustic Noise Evaluation for Overhead Line Conductors using an Anechoic Chamber

Emerging technologies associated with conductors and transmission towers require a re-evaluation of models of audible noise generated by overhead line conductors. Measurements on which existing commercial models were developed were typically performed on a single, classical design of conductor around 50 years ago. Within this article a testing facility employing a semi-anechoic chamber and a novel measurement procedure are proposed to give a guideline for accurate determination of acoustic emission from overhead line conductors. The reproducibility of these measurements is well above traditional testing methods, but is shown to be heavily dependent on the chosen wetting technique. It is found that to achieve an accurate result, background acoustic noise control is essential within the experiment especially for lower frequencies of power frequency harmonics. Direct comparison is reported of conductor samples with various physical characteristics. The analysis of results not only gives power utilities valuable information for selecting quieter conductors for overhead lines but also identifies the major cause of excessive noise emissions in different frequency spans. It is identified that the level of corona discharge is close related to high frequency noise (typically above 1 kHz), while the characteristics (size and distribution) of droplets determine the low frequency noise (pure tone).