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HVDC transmission has ___________ as compared to HVAC transmission.
smaller transformer size
smaller conductor size
higher corona loss
smaller power transfer capabilities
smaller conductor size
HVDC transmission requires fewer conductors because it does not have the skin effect or the charging current issues associated with HVAC systems, allowing for better utilization of the conductor cross-section. Additionally, because there is no reactive power flow or frequency-dependent impedance, the system is more efficient regarding dielectric and thermal insulation requirements.
HVDC transmission requires fewer conductors because it does not have the skin effect or the charging current issues associated with HVAC systems, allowing for better utilization of the conductor cross-section. Additionally, because there is no reactive power flow or frequency-dependent impedance, the system is more efficient regarding dielectric and thermal insulation requirements.
VpeakтАЛ=2тАЛVrmsтАЛ тАФ The peak voltage stress in HVAC requiring thicker insulation
IDCтАЛ=JтЛЕA тАФ Uniform current density in HVDC conductors
In HVAC, the skin effect forces current to flow near the outer surface, necessitating larger conductors to manage current density. In HVDC, the current distribution is uniform across the conductor cross-section. Furthermore, the insulation requirement for HVDC is lower because the peak voltage of AC is 2тАЛ times the RMS value, whereas the DC voltage remains constant, leading to smaller conductor and insulation volumes.
HVDC has no skin effect, leading to uniform current density throughout the conductor.
HVDC cables are not subject to charging currents that limit transmission distance in AC.
The absence of reactive power flow in HVDC simplifies conductor design.
Corona loss is significantly lower in HVDC compared to HVAC for the same power rating.
Reduced conductor material requirements
Lower dielectric loss and corona loss
Elimination of reactive power compensation (no charging current)
Asynchronous interconnection of different power grids
Expensive converter stations required at both ends
Complexity of DC circuit breakers
Generation of significant harmonics requiring large filters
Long-distance bulk power transmission
Submarine cable power links
Asynchronous interconnection of regional grids
| Feature | HVDC | HVAC |
|---|---|---|
Conductor Size | Smaller | Larger |
Skin Effect | Negligible | Present |
Option A is incorrect because HVDC converter stations (using valves and transformers) are often bulkier than simple HVAC substations.
Option C is incorrect because HVDC generally experiences lower corona loss than HVAC due to the absence of the fluctuating voltage cycle.
Option D is incorrect; HVDC has superior power transfer capabilities over long distances.
B is correct тАФ HVDC systems require a smaller conductor size due to the absence of skin effect and improved voltage-to-insulation efficiency.
Always remember that in HVDC, the absence of skin effect allows the entire cross-section of the conductor to carry current, making it more efficient than HVAC for bulk power transmission.