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When continuous ground currents are inevitable then ____________ system is preferable.
Monopolar
Homopolar
Bipolar
Back to back
Homopolar
A Homopolar HVDC system utilizes two or more conductors having the same polarity (usually negative) with the ground serving as the return path. This configuration is specifically chosen in scenarios where continuous ground currents are unavoidable or acceptable, often utilized in early stages of HVDC implementation or specific monopolar earth-return designs.
A Homopolar HVDC system utilizes two or more conductors having the same polarity (usually negative) with the ground serving as the return path. This configuration is specifically chosen in scenarios where continuous ground currents are unavoidable or acceptable, often utilized in early stages of HVDC implementation or specific monopolar earth-return designs.
IgroundтАЛ=тИСIconductorsтАЛ тАФ where ground current is the algebraic sum of all conductors
In a homopolar system, all conductors are operated at the same polarity relative to ground. Because the ground provides the return path for the circuit, a continuous current flows through the earth. This design is primarily used to minimize the number of insulated conductors required when the insulation requirements of the return path are non-critical, or when environmental regulations allow for constant earth-current leakage.
Operates exclusively with a single polarity (negative is preferred to minimize corona).
Requires only one type of insulation (same polarity).
Ground current is continuous, which can cause interference with nearby communication lines.
Used when the cost of a metallic return is prohibitive or unnecessary.
Lower insulation costs as all conductors share the same polarity.
Reduces the number of required conductors compared to bipolar systems.
Significant interference with underground metal structures due to continuous ground currents.
Electrolytic corrosion of metallic objects near the ground path.
Early HVDC long-distance transmission lines.
Low-cost rural or industrial point-to-point power delivery.
| Feature | Monopolar | Homopolar |
|---|---|---|
Return Path | Metallic/Ground | Ground Only |
The negative polarity is chosen for conductors in earth-return systems because it results in less radio interference and lower corona loss compared to positive polarity.
Option A (Monopolar) typically uses one conductor, whereas Homopolar utilizes multiple conductors of the same polarity.
B is correct тАФ Homopolar systems are inherently designed to use the ground as a continuous return path for multiple conductors of identical polarity.
Always remember that in HVDC, 'Bipolar' is the standard for modern systems because it eliminates ground current, whereas 'Homopolar' is specifically noted for its continuous reliance on earth return.