EMERGENCY MODES MODELING IN A COMPLEX LOAD NODE: HIGH-FREQUENCY COMPONENTS OF SIGNALS

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The purpose of the study is to show the features of the occurrence of high–frequency components in current and voltage signals in various elements of the electrical complex by the example of modeling emergency modes in power lines and a complex load node and to analyze their mutual influence.
 
 Materials and methods. The signals of currents and voltages during transients in a power line and the load node with a three-winding transformer were modeled using the author’s software. The calculations are based on the method of synthetic circuits (Dommel’s algorithm). The main attention is paid to the occurrence of high-frequency components of current and voltage during short circuits and switching.
 
 Results. Modeling of the three-phase short circuit in a 110 kV transmission line when it is divided into P-sections demonstrates how significantly the level of high-frequency components differs in each of the three phases. This is manifested primarily in voltage signals. In a complex load node with a 110/35/10 kV transformer, short circuits and switching on the 35 kV side significantly affect the currents and voltages on the 10 kV side. It is shown that a higher level of high-frequency components of current signals corresponds to energy recovery modes in case of imbalance and run-out of the powerful asynchronous motor on the 10 kV side. The possibility of using the obtained results for the classification of faults in electrical systems is discussed.
 
 Conclusions. The level and spectral composition of the currents and voltages high-frequency components in transient modes depends on the initial phase and is of interest for the faults analysis and classification. The nature of these oscillations is determined by the resonant frequencies of the electrical circuits that occur during switching and short circuits.