A CHOICE OF CRITICAL SECTIONS OF ELECTRIC WIRES AND CABLES IN POWER CIRCUITS OF ELECTRICAL EQUIPMENT OF POWER INDUSTRY

Abstract

Purpose. Implementation of close calculation determination of critical sections of S Ci and critical amplitudes of density of alternating current δ Ci of frequency 50 Hz in wires and cables of power circuits of electrical equipment of power industry, characterized flowing in it at malfunctions of operation current i k (t) of short circuit (SC) with set amplitude-temporal parameters (ATP). Methodology. Scientific and technical bases of power engineering, electrophysics bases of technique of high-voltage and large pulsed currents, theoretical bases of the electrical engineering. Results. The results of the developed electrical engineering approach are resulted in a calculation choice on the condition of electric explosion (EE) of current-carrying parts of cable and conductor products (CCP) of critical sections of S Ci for the copper (aluminum) cores of the uninsulated wires, and also for the insulated wires and cables with a polyvinilkhloride (PVC), rubber (R) and polyethylene (PET) insulation with copper (aluminum) cores (shells) on which in the power circuits of electrical equipment of the general industrial equipment in malfunction the current of SC i k (t) flows with set ATP. On the basis of determination of sizes of the real critical sections S Ci for the indicated wires and cables the calculation numeral estimation of critical amplitudes of density δ Ci of SC current i k (t) is executed with set ATP in current-carrying parts of investigated CCP of power circuits of the examined electrical equipment. It is determined that in the power circuits of electric equipment of the general industrial installations (for permanent time of slump of T a =50 ms of аperiodic to the constituent of current of SC) critical amplitudes of density δ Ci of SC current i k (t) at time of his disconnecting t k =100 ms in copper (aluminum) cores for the uninsulated wires and insulated wires (cables) with copper (aluminum) cores (shells), PVH, R and PET it is numeral made an insulation according to approximately 1,57 (1,18) kA/mm 2 . At time of disconnecting t k =160 ms of SC current i k (t) in the power circuits of the examined electrical equipment (T a =50 ms) critical amplitudes of density δ Ci of SC current i k (t) for the copper (aluminum) cores (shells) of indicated CCP become accordingly numeral equal approximately 1,33 (0,99) kA/mm 2 . Originality. First by a calculation way taking into account information for ATP of SC current i k (t) and quantitative values of time of his disconnecting t k in the power circuits of electrical equipment of the general industrial installations the numerical values of critical sections S Ci and critical amplitudes of density δ Ci of AC SC current i k (t) are certain for the uninsulated wires, and also insulated wires and cables with copper (aluminum) cores (shells), PVH, R and PET insulation. Practical value. Obtained results for the critical sections S Ci and amplitudes of density δ Ci of AC SC current i k (t) of frequency 50 Hz (at the period of oscillations of T p =20 ms for of periodic constituent of emergency current of SC) can be utilized in power industry in practice at a choice thermally by a bar to the action of large SC currents i k (t) of CCP with copper (aluminum) bars (shells), intended for reliable operation in the power circuits of electrical equipment of industrial power industry.