The Significance of Cable and Nonlinear Loads to Losses, Voltage Drop, and Harmonics in Remote Off-Grid Systems

Abstract

Powerquality (PQ) is part of low-frequency electromagnetic interference (EMI), which could be present in any system. It is known that nonlinear loads pose PQ problems in large grids, but this problem is even more prevalent in smaller grids. However, the typical methods in addressing PQ problems might not be feasible in remote areas because of their challenging characteristics; hence, alternative approaches are needed. This letter investigates the significance of the cable characteristics and the nonlinear load current amplitude $(I_{\mathrm { load}})$ on the power losses $(P_{\mathrm { loss}})$ , voltage drop $(V_{\mathrm { drop}})$ , and total voltage harmonic distortions (THD $_{V}$ ) to effectively minimize them. The investigated cable parameters were based on the typical cable $2\times 16$ mm2 NFA2X. A high value of $P_{\mathrm { loss}}$ , $V_{\mathrm { drop}}$ , and THD $_{V}$ was found when the loads were highly nonlinear and the cable length was 1 km. A sensitivity showed that $R_{\mathrm { cable}}$ and $I_{\mathrm { load}}$ were more significant than $L_{\mathrm { cable}}$ and $C_{\mathrm { cable}}$ to the increase of $P_{\mathrm { loss}}$ , $V_{\mathrm { drop}}$ , and THD $_{V}$ . Therefore, using more parallel conductors ( $4\times 16$ mm2 NFA2X) as a simple approach was proposed to reduce $R_{\mathrm { cable}}$ and $I_{\mathrm { load}}$ per cable, which resulted in 53%, 53%, and 28% reduction in $P_{\mathrm { loss}}$ , $V_{\mathrm { drop}}$ , and THD $_{V}$ , respectively. The additional cable investment can be recovered by the savings from the $P_{\mathrm { loss}}$ reduction, which was estimated at four years. Moreover, complying with the recommended THD $_{V}$ value (below 8%) was more difficult than keeping $V_{\mathrm { drop}}$ below 10%, because it requires lower $R_{\mathrm { cable}}$ and $I_{\mathrm { load}}$ .