Measurement and Research of the Characteristics of Noise Distribution in Three-Phase Four-Wire Low-Voltage Power Network Channels

This paper reports the measurements and the research of noise characteristics in three-phase four-wire low voltage power network channels with overhead conductor structures. The study focuses on noise classification, loads characterization, the characteristics of noise distribution along the power lines, and that from coupling across different phases. The measured frequencies range from 1 kHz to 1 MHz. Simultaneous measurements of the characteristics of noise distribution were carried out with two sets of instrument of same performance to eliminate the influence of time variance and to improve measurement accuracy. Our results show that: 1) at the frequencies of interest, the noises of power network are mainly produced by the loads. The closer to the noise source (loads), the higher level the noise is. 2) The noise level varies from different coupling phases. The noise level of phase to phase coupling is usually far less than or at least not greater than that of the related two single-phase-to-neutral coupling, respectively. 3) At lower frequencies, the power spectrum density of the power-frequency harmonic noise is much higher than that of the background noise