Volts and Frequencies (UK).
Between 1908 and 1912, the Board of Trade adopted (both for ac and dc) -
115v, 230v, 460v and 525v as standard 'low pressures', at the generator terminals.
At the consumer's terminals this reduced to
110v 220v 440v and 500v, with 3 phase at 380v across principal 220v conductors to neutral.
For high pressure, the Board adopted
2200v, 3300v, 6600v and 11000v at the generator terminals, and at the transformer terminals 2000v, 3000v, 6000v and 10000v
Tramway voltages were set at 500v
Frequency was set at 50hz as standard, with exceptional use of 25hz permitted.
A variation of plus or minus 10% was permitted (then) on voltage supplied.
So it looks like they allowed for losses in arriving at what appears at first to be illogical voltages.
Alan
