Rahimzoda Jamshed Bobomurod, Muqimova Nargis Rustamovna, Umaralizoda Yusuf Mahmadali, Sharipov Erkin Kurbonovich,
Annotation:
The commissioning of new generating facilities, substations, and power transmission lines within the electric power system of the Republic of Tajikistan (EPS RT) enhances the reliability of electricity supply to consumers and creates conditions for the development of new industrial enterprises, thereby contributing to the improvement of public welfare and overall national economic growth. At the same time, the expansion of the EPS RT is inevitably accompanied by an increase in short-circuit current (SCC) levels across networks of various voltage classes, which poses a real risk that the parameters of existing electrical equipment may no longer comply with the new calculated SCC levels. In this paper, the initial periodic components of single-phase and three-phase short-circuit currents have been calculated for 110, 220, and 500 kV electrical networks of the operating EPS RT. Based on the obtained values, the boundary loading indicators of circuit breakers in terms of breaking capacity - both minimum and maximum - 75 have been determined for all considered voltage class nodes. Substations at which the calculated short-circuit current values exceed the rated breaking currents of the installed circuit breakers have been identified. A comparative technical and economic analysis of three alternative solutions has been carried out: the installation of current-limiting reactors, the replacement of oil circuit breakers with modern SF₆ gas-insulated circuit breakers, and the retention of the existing network configuration without modifications. It has been established that the complete replacement of oil circuit breakers with gas-insulated circuit breakers yields the greatest economic effect, while stationary network division (SND) represents the most capital-efficient solution. The economic efficiency of SND as a method for limiting short-circuit current levels in the developing electric power system of the Republic of Tajikistan has been substantiated.
Keywords: short-circuit current, power system, high-voltage circuit breakers, breaking capacity, technical and economic calculation, stationary network division.