These illustrations are from The Modern Plumber and Sanitary Engineer, Vol 5 (Ed. Richard H Bew, Pub. Gresham, London UK) which refers to the 1924 Edition of the IEE Wiring Regulations. The generators are for private electric lighting plants for country houses - mains electricity was still uncommon outside major towns then. The Petter switchboard is for use with the generators for charging batteries for lighting.
Other chapters in the same volume are electric bells (with Leclanche cells), patent glazing, and ship's plumbing.