In this paper the possibility to approximate the frequency response of a three-conductor power cable as a PLC channel by a two-conductor equivalent is investigated. The approximation is useful to perform faster numerical simulations of a PLC channel in the analysis or design of a three-phase PLC channel. The radius and distance between two conductors considered into a homogeneous medium are varied in a statistical way to reproduce the actual three phase PLC channel. In the numerical simulations, nine commercial power cables used in ships are considered, so that the results can be very helpful for users interested in a practical scenario. The results show that the two-conductor approximation can be obtained and it is particularly useful for the power cables of larger cross-section.