Stray Current Protection in Harbor Areas

In harbors, central dc supply equipment is still occasionally used as welding equipment on wharves, travelling dc cranes, dc supply for ships in dock, etc. In Ref. 1 proposals for avoiding stray currents are detailed in which separate dc supply equipment is stipulated. In ac distribution networks in which the subsequent dc network is grounded in only one place, there is no possibility that the dc currents will occur as stray currents. 

Considerable stray currents can, of course, be caused by dc-driven cranes that load and unload ships where the rails act as the return conductor for the current. The rails run parallel to the harbor basin, quay walls of steel-reinforced concrete or steel piling walls. These can take up a large part of the stray current and conduct it further because of their small longitudinal resistance. Noticeable stray current inter- 

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