Currently, in the 0.4 kilovolt distribution electric grid of the Public Joint Stock Company «Rosseti Center and Volga Region» has implemented electricity storage systems designed to improve the quality of electric energy. Evaluation of the effectiveness of their work is of practical importance. (Research purpose) The research purpose is analyzing the application of an electric energy storage system with phase-by-phase power consumption and supplying installed in a rural 0.4 kilovolt grid to improve the quality of electricity. (Materials and methods) For the research was used data from automated dispatch control systems, the Systel operational information complex of the branch of the Public Joint Stock Company Rosseti Center Orelenergo, as well as data from the results of own research. The article presents an analysis of the quality of electricity using a certified electricity quality analyzer RESOURCE-UF2M according to the standard values according to GOST 32144-2013. (Results and discussion) The control algorithms of the electric energy storage system was analyzed. The article presents the disadvantages and advantages of using the studied storage device to improve the quality of electricity in rural electrical networks of 0.4 kilovolts. The influence of the electric power storage system on the quality indicators of electric energy was described. (Conclusions) The use of an electric power storage device with phase-by-phase voltage regulation in the electrical grid made it possible to prevent the phase voltages from going beyond the standard deviation according to GOST 32144-2013. A decrease in the value of the voltage asymmetry coefficient along the zero sequence K0U was recorded by 11.2 times when the electric power storage device was supplying power compared to its operation in the grid monitoring mode.