The paper considers an electrical substation with a voltage of 330/110/35 kV. Means of voltage regulation on the substation autotransformer are investigated. The paper considers the means of voltage regulation on autotransformers of the 330/110/35 kV substation to ensure uninterrupted power supply and the desired voltage level on the busbars of consumers. The choice of the optimal version of the on-load tap-changer of the autotransformer is shown. The electric network with voltage of 110 and 35 kV is considered. The power supply center is substation 330 kV. The connection between voltages is provided by three three-phase autotransformers of the ATDCTN200000/330/110 type. Autotransformers are used instead of three-winding transformers to reduce the cost of conductive material and increase transmission power, but unlike three-winding transformers, they have only one voltage control device - load control regulation. Steady-state and emergency modes are investigated. The PowerFactory program has created a network model, which is used to calculate the mode and evaluate the methods of voltage regulation. On the basis of calculations the point of economic flow distribution in which it is expedient to open a network in a normal mode, and on the switch to provide the device of automatic input of a reserve is defined. The principles of control of modes of operation of electrical systems are investigated: minimum costs for generation, transmission and consumption of electricity (technological losses), reliability of operation of electrical systems, quality of electricity. The purpose of this work is to substantiate the optimal operational scheme of the electrical network, the study of the modes of operation of the 330/110/35 kV network. The simulation of steady and emergency modes is performed in the work. The optimal operational scheme of the electric network is substantiated in order to improve the reliability of power supply and ensure the desired level of voltage on the busbars of consumers.