A concurrently maintainable secondary power distribution system enables redundant secondary power support to electrical loads, which receive independent primary power support from separate primary power systems, via a secondary power busway. Separate bus ducts, each carrying power from a secondary power system, are coupled to opposite ends of the busway. Each bus duct can carry power from a separate secondary power system, and switching devices bridging the connections between the bus ducts and the power busway can selectively switch the power busway from one of the bus ducts to the other bus duct, thereby switching between one of the secondary power systems. The separate secondary power systems can be coupled together at various points in the respective power systems, so that one or more portions of one of the secondary power systems can distribute power received from an upstream portion of another one of the secondary power systems.