FERRORESONANCE OVERVOLTAGES IN ELECTRICAL INSTALLATIONS 6–220 kV: THEORY AND RESULTS OF EXPERIMENTAL STUDIES
Authors:   Omsk State Technical University, Kosarev Boris 
Published: December 2022

Relevance The article is devoted to the systematization and generalization of theoretical and experimental studies of ferroresonance overvoltages in electrical installations 6–220 kV. The need to study this issue is associated with the active introduction of distributed generation facilities into distribution networks, as well as medium and low voltage networks. In power districts with distributed generation facilities, the settings and operation algorithm of relay protection and automation devices differ from the traditional ones used in centralized power supply. The generation parameters and the nature of electromechanical transients also differ, which is caused by the low dynamic stability of generating plants based on synchronous generation and the use of network inverters with energy storage in electronic generation. Thus, due to significant differences in the parameters of the network operation mode with and without distributed generation objects, it is necessary to revise many well-known technical problems, including the issue of ferroresonant processes. Electrical installations of 6–220 kV were chosen as the object of research, since the concept of distributed generation does not imply backbone networks, and the maximum installed power of an individual facility is limited by 25 MW. Aim of Research Aim of research is to systematize and summarize the theoretical and experimental studies of ferroresonance overvoltages in electrical installations 6–220 kV. Research methods To study the circuit-mode conditions for the occurrence of ferroresonant processes in electrical installations of 6–220 kV, an analysis of foreign and domestic publications, standards was carried out, and the theoretical foundations of electrical engineering and the theory of nonlinear electrical circuits were used. Results The physical essence of the phenomenon of ferroresonance, the conditions for the occurrence of ferroresonant processes and measures to prevent them in medium and high voltage networks, experimental studies of ferroresonant processes are considered. The ferroresonant process consists in compensating the inductive and capacitive resistances in the oscillatory circuit with a saturated inductance core. There are various modes of ferroresonance, which are determined by the initial conditions: fundamental, subharmonic, aperiodic and chaotic. A prerequisite for the occurrence of a ferroresonant process is the power of the power source sufficient to saturate the inductance core. Non-linear inductance that can participate in the formation of an oscillatory circuit are voltage transformers, power transformers, shunt reactors. The capacity of the circuit can be a power line, a busbar system, a capacitor bank, shunt capacitors of switches. Hardware and operational measures to protect against ferroresonant processes in electrical installations are aimed at changing the capacitance or inductance of network elements that may participate in the formation of a ferroresonant oscillatory circuit, preventing the formation of such a circuit or reducing its quality factor. The results of experimental studies of ferroresonant processes do not contradict the guidelines for protection against resonant voltage increases in electrical installations. Keywords: ferroresonance overvoltages, distributed generation, ferroresonant process, electrical installation, busbar system, high-voltage switch, non-linear inductance