Development of methodology for identifying and suppressing ferroresonance processes in isolated electrical complexes and systems

This article is devoted to the development of a methodology for identifying and suppressing ferroresonance processes in isolated electrical complexes and systems. The development of distribution networks based on the principle of distributed generation allows for the reduction of transmission losses and the organization of electrical complexes and systems isolated from the Unified Energy System. One of the disadvantages of such systems is their lower dynamic stability compared to centralized power supply. Voltage and frequency deviations in isolated complexes and systems can lead to saturation of the magnetic cores of power transformers, resulting in ferroresonance. This issue remains challenging and poorly understood. Therefore, the objective of this work is to develop a methodology for identifying and suppressing ferroresonance circuits in isolated electrical complexes and systems, taking into account the saturation mode of power transformers and deviations in voltage and frequency from their nominal values. This paper presents the derivation of expressions for calculating the resistance of the magnetizing branch of a power transformer in saturation mode and when voltage and frequency deviate from their nominal values. A method for identifying ferroresonance processes and evaluating control actions aimed at suppressing them based on the amplitude-frequency characteristic of the network is described. The method is tested using the example of an oil and gas production enterprise's electrical transformer substation. According to calculations, a 12 % load on a 35/6 kV transformer in saturation mode of its magnetic system corresponds to the formation of parallel ferroresonance at a frequency of 47.3 Hz and series ferroresonance at a frequency of 72.2 Hz. The ferroresonant process is damped as the transformer load increases. Detuning the ferroresonant circuit by increasing the capacitance from 13 μF to 26 μF corresponds to a shift of parallel ferroresonance to a frequency 36.4 Hz and series ferroresonance to a frequency of 55.7 Hz.