Make a detailed explanation of why a range of voltages is used such as 15 to 25kV at the generators and up to 400kV for transmission, and the reasons for other voltages (e.g. 33kV and 11kV down to 400/230 volts) for light industrial and domestic end users.
The fundamental rationale for transmitting power at high voltages is to maximize efficiency. There are inherent energy losses in the transmission of electricity across vast distances. High voltage transmission reduces the amount of power lost as energy travels from one site to another.
To begin with, there are certain exceptions to the rule that the voltages are all multiples of 11. In 1952, Sweden erected the world's first 380 kV power line, the 952 km Harsprnget - Hallsberg line. The first extra-high-voltage transmission of 735 kV occurred on a Hydro-Québec transmission line in 1965. The first transmission at 1200 kV occurred in the Soviet Union in 1982.
The voltage level began at 110 volts before increasing to 120 volts, 220 volts, and 240 volts for domestic use. Transmission and distribution voltages that are multiples of 11 are 11 kV, 22 kV, 33 kV, 66 kV, 132 kV, and so on.