During the implementation of energy efficiency policy in the Russian Federation, issues related to the analysis of the electric power quality (QE) in the power supply systems (PSS) of industrial enterprises are of particular importance. Much attention has been paid in recent years to the problem of the electric power quality both in our country and abroad due to significant economic damage caused by deterioration of QE indicators. The improvement of the main indicators is an integral part of the energy and resource saving policy, the role and importance of which are ever increasing as part of the implementation of the country's energy program. In the course of work, comprehensive studies of electric power quality indicators were carried out using modern measuring devices (AR5, PKK-57), their further analysis using software (DELPHI, MathCad, Excel) and criterial evaluation of theoretical and experimental studies. A method of experimental study of the amplitudefrequency characteristics of the higher voltage harmonics in the 6 kV power supply system of OJSC Pobedit and OJSC Electrozink has been developed. Comparison of experimental data on the harmonic components of currents and voltages and the data of analytical calculations in Fourier series have shown good convergence of the results. The results of the study of nonsinusoidal voltage in the power supply systems, according to the developed calculation methods, were introduced into production at the enterprises of non-ferrous metallurgy of the Republic of North Ossetia-Alania: OJSC Electrozinc (zinc production), OJSC Pobedit (hard-alloy production).