Why did you use step up voltage inac transmission line?

Thanks for invitation -

Sorry - outside of my specialty   !

Voltage is stepped up in an AC transmission line to reduce the losses in transmission line. As, 

Losses = (I)^2 * R

where, I = Current and R= Resistance

So, if voltage are step down that means current reduced in order to maintain the power constant.

the voltage is stepped up in transmission line to reduce power loss, enable technical and economical transmission line design

I apologize this is out of my specialist

Sorry i am from civil.............

SORRY ....I am civil.....your question for electric 

As mension before to transmision power voltage by step up transformer and transmission lines,this will reduces the losses power transmited. The resistance was  proportional to the current sequared, so power dissipation  W=Current² x Resistance  and the power transmision = Current x Voltage (P=VI)  is constant, thus is beter to reduces the losses with low current and high voltage using step up transformer in the other side step down transformer to reduces the voltage to the desired value such as 132kv to 33kv YY transformers.

Hi,

Electricity is transmitted mainly through overhead lines or underground cables. Due to the resistance of the transmission wires, there is always some loss of power through the heating effect of current. The electricity transmission systems must be designed in ways which reduce this loss as much as possible.

As you know, in transmission lines by considering constant resistance of line, the power loss is proportional to the square of the current, thus a small current greatly reduces heat loss.

Since P=V.I, in fixed power transmission, to step down the current, we should step up the Voltage in transmission. and then step down the voltage in consumer side.

I hope my explanation helps you.