This paper represents analytical interpretation on the electromagnetic interference between open cable trays of solid-bottom type in a nuclear power plant in assumption that the electric-line current is undesirably generated from damaged cable in a cable tray. Based on the superposition principle and Helmholtz's equation in conjunction with both the separation of variables, we employed the mode-matching method to obtain an analytical solution to this electromagnetic interference problem. Using the modal coefficients obtained from a set of simultaneous equations, we computationally derive electromagnetic-field distributions in terms of various geometric parameters. The investigated results provide us with the useful information to estimate that how much the undesired current source influences on the adjacent digital modules.