Vector modeling of the transient process in an electric network with a voltage of 6-10 kV under the action of an automatic transfer switch

Abstract

Introduction. In 6-10 kV electrical networks with high-power induction motors, emergency modes accompanied by voltage sags, motor starts, and self-starts significantly reduce the reliability of power supply. The selection of the Automatic Transfer Switch (ATS) operating speed is of particular importance, as the superposition of self-start transients of motors from different sections can lead to severe additional voltage dips. The existing methods for analyzing transient processes use numerical methods, which limit the study of processes in individual components of the power supply system. Goal. The development and application of a vector model for analyzing electromagnetic transient processes in 6-10 kV electrical networks with high-power induction motors during ATS operation. Materials and methods. A method employing the representation of network components in generalized vector coordinates with a transition to a rotating reference frame is used. Modeling is based on state equations derived using graph theory, with an analytical solution for branch currents under zero and non-zero initial conditions. Results and discussion. Oscillograms of voltages, currents, speeds, and electromagnetic torques of induction motors during ATS operation have been obtained. The influence of motor coasting on the depth of voltage sags and the nature of current overloads is demonstrated. It is established that some motors stall and reaccelerate at reduced voltage, while the load of the backup section experiences only minor parameter deviations. Conclusion. Vector modeling enhances the accuracy of analyzing the initial stages of transient processes and enables obtaining analytical solutions. It expands the possibilities for a well-founded selection of ATS parameters and contributes to the development of methods for calculating transients in 6-10 kV electrical networks.