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Which of the following HVDC scheme is much better as far as the cost of cable is the concern?
monopolar
bipolar
homoploar
back to back
monopolar
A monopolar HVDC link utilizes only one conductor, typically at negative polarity with earth or sea return, which significantly reduces the cost associated with overhead line conductors or subsea cables. By requiring only one cable instead of two (as in bipolar) or multiple, the overall capital expenditure for the transmission link is minimized.
A monopolar HVDC link utilizes only one conductor, typically at negative polarity with earth or sea return, which significantly reduces the cost associated with overhead line conductors or subsea cables. By requiring only one cable instead of two (as in bipolar) or multiple, the overall capital expenditure for the transmission link is minimized.
CtotalтАЛтЙИn├ЧCcableтАЛ тАФ where n is the number of conductors and CcableтАЛ is the cost per unit cable.
In a monopolar scheme, a single insulated conductor carries the full current, while the ground or a dedicated return path acts as the second conductor. This configuration is preferred for subsea power transmission where the cost of cable is the primary economic factor, as it avoids the need for an expensive metallic return cable while limiting insulation costs to a single conductor.
Monopolar HVDC schemes use ground or sea return to reduce infrastructure requirements.
Bipolar systems use two conductors, doubling the conductor cable cost compared to monopolar.
Ground return can cause issues like soil electrolysis and interference with neighboring metallic pipes.
Used extensively in long-distance submarine cables where cable insulation and laying costs are dominant.
Lowest capital cost due to single conductor usage
Simpler converter station architecture
Ideal for low-power long-distance transmission
Lack of redundancy (fault results in total link failure)
Earth return can cause environmental and corrosion issues
Higher harmonic interference compared to balanced bipolar systems
Subsea interconnections
Long-distance power delivery in sparsely populated areas
| Feature | Monopolar | Bipolar |
|---|---|---|
Number of Conductors | 1 | 2 |
Relative Cost | Low | High |
Back-to-back HVDC schemes are typically used for frequency conversion between two AC systems sharing the same substation location.
Bipolar schemes are preferred for high reliability, as they can operate in monopolar mode if one pole fails.
A is correct тАФ The monopolar HVDC scheme is the most cost-effective in terms of cable expenditure because it utilizes only one primary transmission conductor.
Always remember that in transmission line design, the number of conductors is the most significant factor affecting total capital cost, but reliability (N-1 criterion) usually forces a move to bipolar or multi-terminal configurations for critical infrastructure.