Why not 400KV to 11KV Step Down Transformer Directly Used in a Transmission System?

 

Fig- Typical Electricity Network System

The electricity network system mainly works under three major sects- Power Generation, Power Transmission, and Power Distribution.

Why can't we step down 400KV direct to 11KV in a transmission system?

To find the answer to why we cannot use the high-voltage or extra-high voltage step down directly to the distribution level voltage, let us know the transmission and distribution voltage level from the generation station to the user connection point.

Electricity Generation Voltage

Electrical Power Transmission Line Parameters

What is Electrical Power Transmission Lines? 

The electrical power transmission line is used to transmit electrical power from the source points like generating substation or grid substation to the load point like main distribution substation or various distribution units. 

Electrical Power Transmission Line transmits the wave of voltage and current from one end to another. The electrical energy transmission line is made up of a Copper or Aluminium conductor having a uniform cross-section along the line. 

In overhead power transmission lines, the air between the conductors acts as an insulating or dielectric medium. In the case of underground power transmission line conductors are very closed to each other and is separated by some insulation materials like- insulating paper, XLPE (crossed link polyethene), etc.

Phase gap or safety clearance between exposed overhead live line and ground, the distance between the line and ground is much more. The electrical tower is used for supporting the conductors of the transmission line to keep in safe height from the ground.

The main factor of any electrical power transmission line is the transmission tower. The Main parameters of high voltage transmission lines mainly depend on voltage level.  There are different types of towers use for electrical power transmission lines. The major types of Transmission towers can categorize as bellow.

1. Suspension Tower
2. Tension Tower
3. Transposition Tower [0-10 degree tension towers (TD1)10- 30 degree tension towers (TD3)30-60 degree tension towers (TD6)]
4. Special Tower

The tower is made up of steel for providing high strength to the conductor. For transmitting high voltage, over a long distance, a high voltage direct current is used in the transmission line.

Parameters of Electric Transmission Line

Electrical power transmission line mainly contains four parameters as below:

1. resistance; 
2. inductance;
3. capacitance, & amp;
4. shunt conductance.

The performance of the transmission line depends on the parameters of the line. The transmission line has mainly four parameters, resistance, inductance, capacitance and shunt conductance. These parameters are uniformly distributed along the line. Hence, it is also called the distributed parameter of the transmission line.

The resistance of Electric Transmission Line

AC resistance of a conductor in an electric transmission line cannot be calculated due to frequency and phase changing continuously. Based on the calculation of DC resistance of the transmission line conductor, AC resistance is calculated.

If the DC current is flowing along a round cylindrical conductor, the current is uniformly distributed over its cross-section area.