The paper deals with the power aspect of the electrical design of Trawsfynydd nuclear power-station. It gives the reasons for the unusual system design, describes the problems encountered in choice of gas-circulator drive, and explains the reasoning behind the choice of the essential-supplies system. Cable design in nuclear-power stations presents problems to the designer, and a description is given of some of its facets. Some details of the novel low-frequency control-rod system are given.