Abstract <p>Russian regulatory documents define protection zones for a limited number of simple lightning rods, which is not sufficient for designing optimal lightning protection for complex facilities. A numerical method for calculating the zones protected by complex lightning rod system is presented. The method proposed is based on replacing the earth wire with a system of vertical lightning rods. An analytical expression for the zone protected by a combined (earth-wire–rod) lightning-protection system is derived. The zones protected by tilted earth wires, combined systems, and arbitrary-type earth wires are calculated. Using the example of a closed earth wire, the advantages of the developed technique in comparison with the regulatory documents currently in force are shown. Namely, the accuracy of the solution is enhanced (with improved smoothness of the protected-zone outlines) by taking into account the mutual influence of all lightning-rod -system elements. V.M. Kuprienko’s proposal to choose the maximum distance of a double lightning-rod system based on the active part of rods is investigated, including the results of its application for calculating the protection zones of the Konda oil storage facility (before the accident in 2010).</p>