This article shows about, why high voltage transmission is required in transmission of electrical power. The Alternating supply generated from generating station preferably transmitted with high voltage level. Because transmission of supply with high tension supply has numerous advantages as follows
Advantages of High voltage transmission
- As current level is small compared with low voltage line for same amount of power transfer. So small cross section cross section area conductor can be used.
- Due to less magnitude of current , losses in transmission lines are very low. So Transmission efficiency increases.
- Less line losses cause small voltage drops along transmission lines. So voltage regulation is better
- The capacity of transmission lines depends on amount of power transferred to utility areas. The conductor size is depends on current level transmission line conducted in it. Further it is not depends on voltage level. Hence using proper size conductors , we can transfer more power.
- Increased surge impedance loading
We shall discuss about above factors in brief here,
1. Reduction of cross section area of conductor
The power transmitted through transmission line expressed as
So we get line current flowing though line as from above equation as follows
Further resistance of a conductor
Where,
R = Resistance of conductor in Ohm
L = Total length of conductor in Metre
a = cross section area of conductor metre2
p = Specific resistance of conductor in Ohm – mtr
While current flowing through conductor , some amount of power losses in form of heat. These losses called as copper loss. It stated as follows
Substitute power equation and resistance equation mentioned above with this equation, we get
From above equation it shows that cross section area (a) of conductor is inversely proportional to square of transmission voltage (VL) while remaining parameters are kept constant.
2. It increases transmission efficiency
The line current flowing though transmission conductor can be determined as
From above equation , it shows that current flowing in transmission ,conductor is inversely proportional to the magnitude of transmission voltage. As transmission voltage increases , lines current reduces for same amount of power. So it reduce copper losses in transmission lines. Thus transmission efficiency increases.
3. Better Voltage regulation
During high voltage transmission , line losses reduces. So voltage drop along with transmission lines reduces. Hence no power losses occurred in transmission line. Thus sending end voltage (Vs) is almost equal to the receiving end voltage (Vr). So better voltage regulation obtained in high voltage transmission.
4. Transmission capacity increases
Power transferred through transmission line given by
Where,
Vs = Sending end voltage
Vr = Receiving end voltage
𝛿 = Load angle
X = Line reactance
A transmission line known as better regulation when Vr =Vs
So considering sending end voltage (Vr) equal to receiving end voltage (Vs)
P = Vs2/X
P α Vs2
The capacity of power transmission is directly proportional to square of sending end voltage. So increase of transmission of voltage increases capacity of transmission system. Thus more power can be delivered to utilities. But increase of voltage level more and more , increases cost of transmission system components such towers, insulators etc. However cost is proportional of transmission voltage rather than square of voltage. So graph plotted between transmission voltage and cost of transmission components. The economical
5. Increase surge impedance loading level
Surge impedance loading level is a method expressed the load carrying capability of line when transmitted load is equal to surge impedance of line
Where,
L = Series inductance
C = Shunt capacitance per unit length
]The surge impedance loading for transmission line is given in between phase to neutral line
The surge impedance voltage always varies with operating voltage . This indicates increases voltage level , surge impedance loading also increases. So power transmission capacity ,also increases with transmission voltage level
Those above benefits , we need high voltage transmission required though out all places
