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simply i need to ask that why we do transmission on high voltages why not on low voltages?
By a simple sense power transmission for higher voltages is more practical, economical, and safe. Practical in the sense that we need to use smaller diameter cables for transmission (higher the voltage lesser the current). Economical as relative to the preceding statement for using smaller cables not like the ones with big cores and special insulations which are costly, while high voltage ones are only bare cables. It will also cause a lesser losses in the lines considering less prone to reactance because it is usually situated in high locations and less structures. It is more safe as it is regulated by law and always located away from inhabited areas.
Dear,
When we talk about Trasmission Line, so let me help you to understand.
One of the key concerns in the transmission of electricity is the power loss in transmission lines, dissipated as heat due to the resistance of the conductors.
High-voltage transmission lines are used to transmit electric power over long distances. Normally, high voltage (HV) transmission power lines are made of high voltage (between138 and765 kilovolts) conducting lines of copper and/or aluminum.
Assume the power to be transmitted is P, and the resistance of the transmission line is r.
If the power is transmitted with voltage V, then the current flow through the transmission line is I=P/V.
The power loss Ploss=I2*r=(P/V)2*r
Since P and r are fixed conditions, less power will be lost if high voltages V are used.
Some students will raise questions like: From Ohm's law. if the voltage is increased, the current will increase ,too. Why is the current smaller when high voltage is used to transmit the power.
Textbooks forgot to tell students that the transmission line needs a transformer to step down the voltage.
And the transformer does not have a fixed impedance. If higher voltage is used to transmit the power, the ratio of the transformer will also change which will change the impedance of the transformer.
The following applet was developed to help you understand the high power transmission line.
You can change the Power/Voltage V and resistance r in the transmission line with sliders.
I will show current flow through the transmission line.
Z is the total impedance of the transmission line, Zt is the impedance of the transformer.
N:n shows the ratio of the high voltage transformer (Assume user voltage is100V).
Efficiency of the power line is also shown at the right side.
Done and hope that I help you to understand more about power transmission line.
To reduce conductor cross section. Which help to reduce loss,cost and infrastructure.
we stepup voltage because at low voltage there is high current and then would be high cost of transmission while in high voltage there is't high current so transmission cost would be low. for high current we need a wire with extra large diameter which is very expensive way
Because of the power loss of transmitting over long distances because of the resistance in the wires
opposes the flow of current (Amperes). Power consumed (as heat) in a conductor is
P = I2 X R
To reduce power loss in a wire, reduce the current flowing through it. So if you need X-megawatts of power transferred, use the highest voltage available
P= V X I P is Haigh and V is High I is low and R is low
we use many kilo Volts to transfer power to long distance but its dangerous for consumers so we set down the volts to220 V by many trnsforers to by safe for consumers
breifly , in higher voltage current is lower and if current is low so the losses of grid is lower .
Economy is the key factor and High and Extra High voltage can only transmit power to remote points.
Beside Line Losses, High Voltages also help to eleminate any type of remote Area Electrical Theft which may be done due to normal11 KV or400 Volt System .................
we used this for mantain the power factor. The power loss Ploss=I2*r=(P/V)2*r
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