TOWARDS BROADBAND OVER POWER LINES SYSTEMS INTEGRATION: TRANSMISSION CHARACTERISTICS OF UNDERGROUND LOW-VOLTAGE DISTRIBUTION POWER LINES

Abstract

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 simplifled approximation concerning three-phase N-conductor underground cables is also presented. Taking the generalized analysis and the simplifled 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 verifled that the attenuation in overhead and underground BPL channels depends drastically on power distribution grid type, MTL conflguration, and cables used. Moreover, the attenuation in underground LV/BPL channels exhibits a lowpass behavior, is signiflcantly 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