Towards Broadband over Power Lines Sys- Tems Integration: Transmission Character- Istics of Underground Low-voltage Distri- Bution Power Lines

A complete methodology is employed to determine the transmission characteristics of low-voltage/broadband over power lines (LV/BPL) channels associated with underground power distribution networks, in the light of the multiconductor transmission line (MTL) theory. The established bottom-up approach, already used to treat overhead and underground MV/BPL transmission, is extended to analyze BPL transmission in three-phase N -conductor underground lines with common shield and armor. This analysis shows that these cables may support N + 2 modes, giving rise to N + 2 separate transmission channels which reduce to N+1 if the armor either does not exist or is grounded and to N if the shield is also grounded. In addition to the generalized analysis, a simplified approximation concerning three-phase N -conductor underground cables is also presented. Taking the generalized analysis and the simplified approximation into account, their numerical results concerning attenuation in various underground LV/BPL channels in the frequency range 1–100MHz are validated against relevant sets of simulations and measurements with satisfactory accuracy and compared to corresponding results of overhead and underground MV/BPL channels. It has been verified that the attenuation in overhead and underground BPL channels depends drastically on power distribution grid type, MTL configuration, and cables used. Moreover, the attenuation in underground LV/BPL channels exhibits a lowpass behavior, is significantly higher than that of overhead MV/BPL ones, and is comparable to that of underground MV/BPL ones. A consequence of the proposed methodology is that it Received 24 January 2012, Accepted 14 February 2012, Scheduled 22 February 2012 * Corresponding author: Athanasios G. Lazaropoulos ([email protected]).