Influence of Metal Installations Surrounding the Feeding Cable Line on the Ground Fault Current Distribution in Supplied Substations

This paper presents the method for taking into consideration the influence of metallic installations surrounding the feeding line on the ground fault current distribution in supplied substations. When a ground fault occurs in a substation supplied by a cable line, these installations can significantly participate in reducing the part of the ground fault current emanating through the grounding system of this substation into the surrounding earth. Since only this part of the ground fault current creates potentials on the grounding system, this also means the reduction of all potential differences (touch and step voltages) appearing during the ground fault inside and in the vicinity of the supplied substation. However, current analytical expressions for the determination of the cable line reduction factor do not take into consideration this favorable effect. It is also not possible to determine it by direct measurements. This paper presents a method which enables us to achieve this by using the results of reduction factor measurements and by modeling surrounding metallic installations as a single equivalent conductor, cylindrical in form and parallel with the cable line.