Estimation of the effect of the levels of asymmetry and higher harmonics on the current in the zero working conductor of the 0,38 kV network

One of the problems of modern systems of rural and urban power supply is the presence in a huge number of nonlinear loads that generate high-harmonic currents in a three-phase four-wire network with a voltage of 0,38 kV. Single-phase switching of loads and their accidental power consumption lead to another problem of the above-mentioned power supply systems, namely, to the appearance of unbalanced currents. When non-sinusoidal and unbalanced currents flow through a three-phase four-wire network, additional voltage drops occur on the elements of the electrical network and, as a result, unbalanced phase voltages are installed on the low voltage side of transformer substations 6-10/0,4 kV. Most of the6-10/0,4 kV power transformers have "star / star with zero" winding connection schemes that do not prevent the passage of zero-sequence currents and currents of higher odd harmonics, especially multiples of three. These reasons reduce the quality and efficiency of electric power transmission. The paper studies the regularities of the influence of nonlinear loads on the ratio of the main components of the current in the zero working wire of a three-phase four-wire network with a voltage of 0,38 kV. The results of these studies will be useful for developers of technical means that reduce the level of asymmetry and non-sinusoidal currents in four-wire electrical networks.