224 / 2018-09-22 17:42:31

Comparison of Audible Noise from HVAC and HVDC Overhead Line Conductors

overhead line,audible noise,HVDC transmission line,corona discharge,conductor,anechoic chambers,hum noise,sound pressure level

Purpose/Aim
Audible noise (AN) emitted from overhead line conductors has been investigated through construction of semi-anechoic chamber within a high voltage laboratory in previous work. The breakdown of the air insulation through corona, and the movement of dielectric water droplets is pivotal to the noise production. It is identified that sound control is essential in making accurate measurement for AN within a noisy environment such as HV lab. However DC tests for conductors have not been performed in such an environment before. This article aims to report the sound characteristics (in both time and frequency domain) for HVDC testing on service-aged conductors within a semi-anechoic chamber. Comparison between AC and DC results is intended to investigate the key factors for noise emission in future HVDC transmission lines.
Experimental/Modeling methods
Aged overhead line conductor samples were tested through a cage experiment within an anechoic chamber. Sound pressure levels were measured within three conditions (dry, continuous spray and post-spray). Recorded sound signals are then analyzed in both the time and frequency domain. Comparison has been made between AC and DC voltage supply.
Results/discussion
A remarkable difference in sound pressure level (SPL) between positive and negative DC testing is observed. The effect on the stranding shape of overhead line conductors is evaluated in both DC and AC conditions.
Conclusions
It is concluded that the space charge formed surrounding HVDC lines has a significant effect on the noise level. As a result the positive and negative polarities behave very differently. New prediction methods need to be developed for new conductor geometries types (such as trapezoidal strands).