Lightning Surges in the Electric Network of a Ship: A Study With Respect to Equipment Immunity Levels

Within the extensive electrification of all onboard systems, the mitigation of lightning-induced effects on maritime electronic and telecommunication equipment has gained importance. Despite the progress in standardization, the required surge immunity level remains particularly low. This work provides a quantified overview of the maximum surges induced in numerous points throughout the electric network of a full-scale bulk carrier model via extensive electromagnetic simulations. The major parts of the cabling routes were embedded in the model, and various lightning waveform and strike point scenarios were examined. Multiple violations of the immunity test level were detected, highlighting the need to increase the specifications at least by two discrete test levels of IEC 61000-4-5 or by introducing arbitrary higher test levels and to differentiate the test level according to the location of the load. For loads either exposed on the deck surface or located inside the hull in the bridge area, close to other openings, or with a highly inductive power factor, higher overvoltages were observed. Surge protective devices should be installed adopting a balanced rationale that covers both the need to protect critical loads and the limitations for the stray capacitance they introduce to the system.