New technical developments, such as in the field of frequency drives of technological units, electrified transport, wind, and solar power plants, apply devices built on the basis of powerful transistors. Modern devices designed on these elements are powerful generators of higher harmonics of currents that penetrate the grids of power systems. It requires the development of measures and means to limit the higher harmonics of currents in the electrical grids.
The method and the means of determining the voltage distortion coefficient by higher harmonics in electric networks are considered in the paper. This factor belongs to the group of main indicators of electricity quality, which are regulated by national standards and international standards for electricity quality. The shortcomings in the existing methods are pointed out and a method is proposed which allows increasing the accuracy of the specified indicator significantly. Based on the actual measurement and using certified equipment, it is shown that the error of the measurement results and their calculation by using the proposed method does not exceed 1 % of the nominal voltage, while the existing norms of this factor, depending on the voltage of the power supply system, regulate value of error from 2 % to 8 %. Considering that the commonly used measuring equipment does not take into account the interharmonics and exponential components in the supply voltage, the proposed method regarding these components over a predetermined time interval, much larger than one period, provides higher accuracy for determining the distortion factor. By examining all harmonics and interharmonics, including zero and exponential components, we provide substantially higher accuracy than the existing methods described in the standards and norms for electricity quality.
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