Answer
A higher voltage means a lower current.
Work Step by Step
The power transmitted is P = IV, where I is the current, and V is the voltage between the transmission lines and the ground. The higher the voltage, the lower the current can be to transmit the same power.
The transmission lines have resistance and some electrical energy is changed to heat as they carry current. For a length of wire with resistance R, and carrying a current I, the power loss is $P=I^{2}R$.
Maximizing the voltage V serves to minimize the current I, which minimizes the power losses.
