Answer: Electrical transmission lines are classified primarily based on two key factors: the length of the line and the voltage level they carry.

• By Length: This is the most common method of classification, as the length determines the electrical model used for analysis.

  • Short transmission lines: Generally, lines with a length of up to 80 km (50 miles). For these lines, the effects of capacitance are negligible and are not considered in calculations.

  • Medium Transmission Lines: Lines ranging from 80 km to 240 km (50 to 150 miles). For these, the capacitance effects are significant and are accounted for by using a "lumped" model where capacitance is concentrated at one or more points along the line.

  • Long Transmission Lines: Lines that exceed 240 km (150 miles). For long lines, all electrical parameters—resistance, inductance, and capacitance—are considered uniformly distributed along the entire length, requiring more complex analysis.

• By Voltage: Transmission lines are also categorized by the voltage they carry. While specific ranges can vary by region, a general classification includes:

  • Low Voltage (LV): Up to 1 kV.

  • Medium Voltage (MV): 1 kV to 69 kV.

  • High Voltage (HV): 69 kV to 230 kV.

  • Extra-High Voltage (EHV): 230 kV to 800 kV.

  • Ultra-High Voltage (UHV): Above 800 kV.