Answer: The primary difference lies in their length and the way their electrical parameters (resistance, inductance, and capacitance) are considered in analysis.

• Short transmission lines: Typically less than 80 km in length with voltages below 20 kV. For these lines, the effects of capacitance are considered negligible, and the line is modeled as a simple series circuit with only resistance and inductance.

• Medium transmission lines: Have a length between 80 km and 250 km, with voltages between 20 kV and 100 kV. The capacitance effects are significant and are accounted for by lumping the capacitance at one or more points along the line (e.g., Nominal-T or Nominal-Pi methods).

• Long Transmission Lines: Are over 250 km long and operate at voltages above 100 kV. For these lines, all three parameters (resistance, inductance, and capacitance) are distributed uniformly along the entire length, requiring more complex analysis using distributed parameter models.