Street Lighting Circuit Analysis
If you have a three-phase overhead supply to your house with street lights on the same circuit, these are reticulated with an extra pair of wires runneng through the neigbourhood.  Exche streetlight is connected between the live and neutral wires.

The supply originates at a MV supply transformer and a light sensitive or timer control circuit drives a contactor that supplies up to about 100 streetlights.

The impedance of the copper supply wires are know as well as the distance between poles and the wattage of each lamp.  (New 70 W high-pressure sodium luminaires were installed in my street less than a week ago, replacing mercury vapour to save electricity :-) 

It should be easy to trace the circuit from the supply transformer and draw the circuit diagram to calculate the voltage drops.