AC vs. DC Transmission: Advantages and Disadvantages

This article compares AC (Alternating Current) and DC (Direct Current) transmission, highlighting their differences, advantages, and disadvantages.

Advantages of DC Transmission

• Fewer Conductors: DC transmission requires only two conductors.
• Reduced Inductance, Capacitance, and Phase Displacement Issues: DC transmission doesn’t suffer from the inductance, capacitance, and phase displacement problems that are common in AC transmission.
• Lower Voltage Drop: The voltage drop in DC transmission is less than in AC transmission for the same load and sending-end voltage.
• Full Conductor Utilization: The entire cross-section of the conductor is utilized in DC transmission because there’s no skin effect.
• Reduced Stress on Insulating Materials: DC lines experience less stress compared to AC lines for the same voltage value on insulating materials.
• Lower Corona Loss and Reduced Interference: DC lines have less corona loss and reduced interference in communication electronics.
• Stable System: DC transmission systems are stable, unlike AC transmission systems which can be unstable.

Disadvantages of DC Transmission

• Difficult High-Voltage Generation: Generating power at high DC voltages is difficult due to commutation problems. Furthermore, it cannot be easily utilized at the consumer load.
• No Step-Up/Step-Down Transformation: Step-up or step-down transformation of DC voltages is not possible with equipment like transformers.

Advantages of AC Transmission

• Easier High-Voltage Generation: Power can be generated at high voltages without the commutation problems faced by DC systems.
• Convenient Voltage Transformation: AC voltages can be conveniently stepped up or stepped down using transformers.
• Reduced Losses at High Voltage: High-voltage AC transmission reduces power losses.

Disadvantages of AC Transmission

• Inductance and Capacitance Issues: Problems of inductances and capacitances exist in transmission lines.
• Skin Effect: Due to the skin effect, more copper is needed for transmission.
• Complex and Costly Construction: The construction of AC transmission lines is more complex and costly.
• Increased Effective Resistance: The effective resistance of AC transmission lines is increased due to the skin effect.