On Power Transmission Lines, why are there 3 wires?
The power is 3 phase power. No all three are hot, the voltage between any two is the line voltage. All three wire or conductors are phase conductors.
There is no neutral conductor, the smaller wire often seen is a ground wire or ground conductor. This is not the same as a neutral. The neutral is a current carrying conductor the ground wire only carries current in a fault condition.