Broadband Transmission via Underground Medium-Voltage Power Lines—Part I: Transmission Characteristics

The transmission characteristics of underground medium-voltage/broadband over power line (MV/BPL) channels are examined analytically. By appropriately modifying multiconductor transmission-line theory, the bottom-up approach, already used to treat overhead MV/BPL transmission, is extended to analyze BPL transmission in three-phase underground MV lines with common shield and armor. ThIS analysis shows that these cables may support five modes, giving rise to five separate transmission channels which reduce to three if the shield and armor are grounded. The numerical results concerning attenuation in underground MV/BPL channels have been validated against relevant sets of measurements and compared to the relevant results of overhead MV/BPL channels. It has been verified that the attenuation in underground MV/BPL channels exhibits a lowpass behavior and is significantly higher than that of overhead ones.