HVAC and HVDC Transmission Systems
HVAC and HVDC transmission systems serve different purposes and have distinct characteristics. HVAC is suitable for shorter distances and is less expensive, while HVDC is preferred for long-distance transmission with advantages like lower losses, smaller conductor diameter, and less interference. The choice between HVAC and HVDC depends on factors such as distance, cost, and specific transmission requirements.
Difference between HVAC and HVDC Transmission Systems
| Basis of Difference | HVAC Transmission | HVDC Transmission |
|---|---|---|
| Full Form | High Voltage Alternating Current | High Voltage Direct Current |
| Description | Transmits AC power at voltages about 33 kV to 230 kV. | Transmits DC power at voltages about 100 kV to 800 kV. |
| Number of Conductors | Requires at least three line conductors. | Requires two conductors in bipolar system and one conductor in a monopolar system. |
| Transformer | Uses transformers for voltage transformation. | Cannot use transformers, as they don’t work with DC. |
| Rectifier and Inverter | Does not require rectifiers and inverters. | Requires rectifiers and inverters as major components. |
| Voltage Transformation Complexity | Involves simple voltage transformation. | Voltage transformation is complex. |
| Suitability | Suitable for distances less than 600 km. | Suitable for high-power transmission at long distances, typically more than 600 km. |
| Corona Loss | More corona loss. | Comparatively less corona loss. |
| Skin Effect | Skin effect due to uneven current density. | No skin effect; current density is uniform in the conductor. |
| Conductor Diameter | Requires a conductor of large diameter due to skin effect. | Requires a conductor of relatively smaller diameter. |
| Right of Way | Broader right of way. | Narrower right of way. |
| Tower Size | Towers are tall. | Requires smaller-sized towers. |
| Submarine Power Transmission | Not preferred due to stray capacitance of cables. | Preferably used for submarine power transmission. |
| Interference | Causes interference with neighboring communication lines. | Does not cause interference with nearby communication lines. |
| Circuit Breakers | Less expensive with a simple design. | Comparatively expensive with a complex design. |
| Utilization of Conductor Capacity | Almost 30% of conductor capacity is wasted due to AC peak ratings. | Utilizes full conductor capacity; peak and average ratings are the same. |
| Cost | Less expensive for power transmission. | Little more expensive than HVAC. |
