Channel Characteristics Analysis of Medium Voltage Overhead and Mixed Overhead/Underground Cable Power Network

This paper analyzes the Medium Voltage (MV) power line channel characteristics with overhead and mixed overhead/underground cable network in China. In order to compare the characteristics such as attenuation and noise between narrow-band (30-500 kHz) and broadband (0.5-20 MHz) channels, some field measurements were performed and Link Quality Index (LQI) was proposed to evaluate the channel conditions at different frequencies. The results show that, in contrast to most Low Voltage (LV) underground cables, the MV overhead lines have much less attenuation over the wide frequency range. However, due to small attenuation and long distance, overhead line usually presents strong multipath effects which lead to fragile landscape of usable frequencies for Power Line Communications (PLC). On the other side, broadcast radios can present dominant narrow-band noises at broadband channels. According to the LQI evaluations, to effectively cope with the great variety of MV channels with unknown characteristics, viable PLC system should flexibly adapt its working frequency to the local channel conditions.