The article presents an originally developed mathematical model intended for determining the distribution of single-pole short-circuit currents in the passive part of the system of submarine optical and submarine power cables, which are incident to overhead lines. A quasi-static treatment is applied. Care is taken of: the present electromagnetic and galvanic coupling, the specific configuration of the system, the electrical and magnetic characteristics of the passive conductors that make up the associated grounding system, the geoelectric properties of the routes on land and in the sea, as well as all other relevant factors essential for the exact solution of the task. The KOTVE program for a digital computer was created based on the mathematical model in question. The same was applied to determine the current state in the passive part of the 110 kV submarine connection Selina - Kulina, during the performance of JKS in the Selina cable station.