I've been curious how the various mains voltages used around the world came into existence for a long time but haven't been able to find any information except "they were arbitrary choices". However, I suddenly realised that all mains voltages that I know of have something in common - they can be divided by 50, 55 or 60 V, which happens to be the standard voltage range of arc lamps, the first common application of electricity. It seems fairly logical to assume that standardised mains voltages such as 100, 110, 120, 150, 200, 220, 230, 240 and 250 V were chosen for connecting multiple arc lamps in series in order to save on copper. The only outlier, 127 V, is derived from a 220 V 4-wire 3-phase network. What do you think about that theory?
