Method for determining quality indices for the electrical power supplied by a three-phase network and devices for implementing the method

摘要

The invention relates to measuring technology. The method for determining the electrical-energy quality characteristics of a three-phase system is based on the determination of its symmetric components, from the amount of which the magnitude of the electrical-energy quality characteristics is assessed. According to the invention, first the amplitude and starting phase of the reference voltages is determined, then a symmetrical three-phase reference system of the positive-sequence voltages is formed, the starting phase and amplitude of which is equal to the previously determined values of the starting phase and amplitude of the reference voltages and the frequency of which corresponds to the mains frequency, and then the reference voltages are subtracted phase by phase from the input voltages and the symmetric components are determined in accordance with the difference between the input voltages and the reference voltages. A variant of the device for carrying out the method contains a device (20) for measuring the symmetric voltage components of the three-phase system, three adding circuits (14, 15, 16), a controllable three-phase generator (17) and a shaper (18). This invention can be applied most usefully in information and measuring systems for determining the electrical-energy quality characteristics of three-phase systems. IMAGE