ДІАГНОСТИКА ВІДМОВ ТРИФАЗНОГО ВИПРЯМЛЯЧА НА ОСНОВІ АНАЛІЗУ ПОКАЗНИКІВ ЯКОСТІ ЕЛЕКТРОЕНЕРГІЇ

The paper deals with the analysis of asymmetric modes of electric networks with an isolated neutral. A single case of asymmetric loading affecting the distribution of currents in phases is analysed. It is shown that in the case of an active resistance connected between the phases without involving other branches, currents with a shift in phase angles occur, which creates the illusion of a reactive load. However, it is proved that the load remains purely active. A method of analysis using a system of linear voltages and currents is proposed, which allows expanding approaches to the assessment of asymmetric modes. The application of the method of calculating linear currents according to the criterion of the least sum of squares of linear capacities for subway power networks is considered. Attention is focused on modelling a subsystem containing a transmission line, a transformer and a rectifier. It is confirmed that the failure of one of the diodes in a six-bridge rectifier significantly affects the functionality of the system, causing current distortion. Various types of diode failures are analysed. It is established that these failures lead to a change in the current waveform, which is confirmed by graphs under emergency modes of operation. The harmonic composition of line voltages and currents was studied, which revealed significant values of current harmonics, while voltage harmonics are of little importance. The asymmetry of the rectifier's operation in case of faults is revealed, which leads to an increase in harmonic distortion and a decrease in the quality of electricity. Such phenomena can cause additional losses in the system and negatively affect the stability of electrical equipment. The obtained results of the study can serve as a basis for the development of new methods for monitoring and improving the characteristics of electric power systems, which is an important task for further research in this area. The results of the study demonstrate the need to take into account harmonic analysis to assess the state of electrical networks. The data obtained can be used to improve the methods of rectifier fault diagnostics and increase the reliability of electric power systems.