To transfer electrical energy of power P over long distance, there will be loss in energy due to transmission. where the poser loss during transmission can be expressed as

$P_c=i^{2}R$

power delivered to be P= Vi

so, power loss during transmission is $P_c=\frac{P^{2}R}{V^2}$

as P² and R being constant, to minimize P_c we need to increase V. so over long distance transmission of electrical energy we need to increase potential.