- Transmission Line Types: Transmission lines are classified into short, medium, and long based on their length and operating voltage.
- Power Loss and Voltage Drop: All transmission lines have some power loss and voltage drop while transmitting power.
- Voltage Regulation: This measures the change in voltage at the receiving end from no-load to full-load conditions.
- Electrical Parameters: The main electrical parameters of a transmission line are resistance, inductance, and capacitance.
- Performance of Transmission Line: The efficiency and voltage regulation are key indicators of a transmission line’s performance.
There are three main types of Overhead Transmission Lines:
- Short transmission line – The line length is up to 60 km and the line voltage is comparatively low less than 20KV.
- Medium transmission line – The line length is between 60 km to 160 km and the line voltage is between 20kV to 100kV.
- Long transmission line – The line length is more than 160 km and the line voltage is high greater than 100KV.
Whatever may be the category of transmission line, the main aim is to transmit power from one end to another.
Like other electrical systems, transmission networks experience power loss and voltage drop while transmitting power from the sending end to the receiving end. The performance of a transmission line is determined by its efficiency and voltage regulation.
Voltage regulation of a transmission line measures the change in receiving end voltage from no-load to full-load conditions.
Every transmission line has three basic electrical parameters: electrical resistance, inductance, and capacitance. These parameters are distributed uniformly along the conductors, which are supported by transmission towers from one place to another.
The electrical power is transmitted over a transmission line with a speed of light that is 3 × 108 m ⁄ sec. Frequency of the power is 50 Hz. The wave length of the voltage and current of the power can be determined by the equation given below,
f.λ = v where, f is power frequency, λ is wave length and υ is the speed of light.
Hence, the wave length of the transmitting power is quite long compared to the generally used line length of transmission line.
For this reason, the transmission line, with length less than 160 km, the parameters are assumed to be lumped and not distributed. Such lines are known as electrically short transmission line. This electrically short transmission lines are again categorized as short transmission line (length up to 60 km) and medium transmission line (length between 60 and 160 km). The capacitive parameter of short transmission line is ignored whereas in case of medium length line the, capacitance is assumed to be lumped at the middle of the line or half of the capacitance may be considered to be lumped at each ends of the transmission line. Lines with length more than 160 km, the parameters are considered to be distributed over the line. This is called long transmission line.
