Abstract
Electrical switching operation in a substation which locates in a high-voltage transmission system alters operating modes of main wiring in either the substation or the system. Major alterations may have negative influences on the switchgear of main wiring in a short time. The quantitative study of this problem has to be based on establishing equivalent circuits of main wiring, when there rarely are formulas to calculate the reactance of tubular busbars. In this paper on the basis of the electromagnetic field theory, the magnetic induction and flux linkages outside and inside tubular conductors are obtained from the Ampere Loop Theorem, and then the formulas to calculate approximately the reactance of tubular busbars with a three-phase parallel arrangement are derived. From the process and results of the calculation in an example it may be seen that the formulas are applied simply, conveniently and rapidly, and may be valuably spread in practical electrical engineering.