Originally posted by: SWORDLOVER
. . . Now the tap changer is not necessary for the LV network, as the traditional LV loads are generally small and operating in a regular way. . .
That is not quite correct. An off-load tap changer is required for the LV network to compensate for the voltage applied to the transformer's primary terminals, depending on its position in the network. Additional load on the LV side may also require a different tap, to set the LV within statutory limits. As Donald said, as on-load tap changers are generally expensive, the "day to day" regulation is carried out at a higher voltage level where fewer devices are required.
In long LV rural overhead networks, regulators are employed at LV, generally to accout for the voltage drop between the supplying substation and that point, such that additional properties may still receive statutory voltage. These will generally be 1:1 transformers with a few taps and a voltage control relay of some sort.
Where single-phase loads are particularly unbalanced, a "balancer" may be employed. Unlike the regulator, the balancer is a purely wound device with no moving parts. It is a cross-connected star - zig zag transformer and "relocates" the system neutral, such that all phase to neutral voltages are the same.