Determining additional power losses in the electricity supply systems due to current's higher harmonics

Abstract

The paper reports results of research into the influence of higher harmonics of the power source voltage and the load current on power losses in an electric network. The relevance of this study is predetermined by the ever-increasing number of the electric energy pulse consumers, which leads to an increase in the number of higher harmonics at power supply systems. In turn, higher harmonics cause deterioration not only in the qualitative indicators for electricity, but a significant reduction in energy efficiency as well. The study that we conducted has shown that existing analytical dependences of a network's active resistance on the higher harmonics' frequencies are mutually exclusive, contradictory, and inaccurate because they do not take into consideration the geometrical characteristics of the network conductors. Based on the first-order Bessel equations, we have obtained refined analytical dependences of a network's active resistance on the higher harmonics' frequencies, taking into consideration the geometrical properties of wires. It has been established that in addition to an increase in the active resistance value due to the influence of a skin effect, higher harmonics predetermine additional losses caused by an increase in the root-mean-square current value. We present the dependence of additional power losses and efficiency factor in the electric network as a function of values for the load current harmonic distortions coefficient and the coefficients for harmonic distortions in a power source voltage. It was established that the network current higher harmonics, caused by the pulse load, lead to the bigger losses in the network than the higher harmonics from the power source. The results obtained in this study could be used in the calculation of energy losses in electric networks due to higher harmonics and while estimating economic efficiency when introducing filter compensating devices.