Improved analytical expressions for the reduction factor of feeding lines consisting of three single‐core cables

The paper presents an original analytical procedure giving analytical expressions for the determination of ground fault current distribution for a fault located anywhere along a feeding line consisting of three single‐core cables. The derived analytical expressions are mathematically rigorous and take into account all the relevant factors without introducing some larger approximations or idealizations of the real electrical circuit. Correct estimation of ground fault current distribution is necessary in contemporary power engineering practice due to at least two important reasons. One of them is the possibility to a correct estimation of dangerous potential differences, touch and step voltage, which may appear during a ground fault at grounding system of the supplied station. The second reason is the possibility to choose single‐core cables of the feeding cable lines with a metallic sheath cross‐section large enough to withstand thermal strains caused by fault currents. The final result of the use of the analytical expressions derived here is the possibility to determine safe and cost‐effective solutions regarding the grounding systems of the supplied stations and regarding the cross‐sections of the metallic sheaths of single‐core cables. The validation of the derived expressions is verified by experimental measurements.