Simulation of losses in LV cables due to nonlinear loads

Abstract

Companies active in distribution or transmission of electrical energy know the power losses in their HV and MV cables. Users have no idea of the magnitude of the cable power losses in their electrical installations. Nevertheless cable power losses can be a significant part (3%–5%) of the total power consumption. Nonlinear loads (ASD, CLF, IT-equipment,…) are often installed with the aim of rational energy use. However, one is not aware of the increase of cable losses due to the nonlinear load. A software tool is developed in order to enable companies to simulate the supply system losses of their present or future electrical installation in an easy way, including the use of both active or passive filter systems. In this paper the power losses in LV cables are analyzed, including the impact of nonlinear loads. A simple model is proposed in order to calculate power losses in a quick way. The model uses an equivalent resistance, taking into account frequency dependency by means of a correction factor only dependent on the conductor cross section and not on the current harmonic spectrum. The model is validated by experiments. Deviations less than 5% are found. Because of the suitability of the model for a wide range of harmonic spectra, power losses can be easily calculated with sufficient accuracy without the knowledge of the current harmonic spectrum. The paper also includes a sensitivity analysis of parameters influencing cable losses and some practical recommendations to reduce cable losses.