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At Higher voltages,┬аbelted cables are more suitable than screened cables
Yes
No
Cannot say anything
Insufficient data
No
Belted cables are restricted to low voltage applications (typically up to 11 kV) because they rely on impregnated paper insulation which is subject to high tangential electrical stresses at higher voltages. Screened cables, such as H-type or S.L. cables, incorporate metallic screens to ensure radial electrical fields, making them suitable for higher voltage levels (up to 66 kV or higher).
Belted cables are restricted to low voltage applications (typically up to 11 kV) because they rely on impregnated paper insulation which is subject to high tangential electrical stresses at higher voltages. Screened cables, such as H-type or S.L. cables, incorporate metallic screens to ensure radial electrical fields, making them suitable for higher voltage levels (up to 66 kV or higher).
EradialтАЛ=rln(R/r)VтАЛ тАФ Electric stress in a single-core cable
EtangentialтАЛюАа=0 тАФ Characteristic feature of belted cables contributing to insulation failure at high voltage
In a belted cable, the three-core insulation is surrounded by a common belt of paper, creating a non-radial electric field. As the voltage increases, the tangential stress between the cores and the sheath insulation becomes excessive, leading to potential dielectric breakdown. Screened cables employ individual metallic sheaths (usually aluminum or copper foil) around each core, which ensures that the electric stress is purely radial, thereby eliminating tangential stresses.
Belted cables use a common paper belt to bind three cores together.
Tangential stress in belted cables is the primary cause of dielectric failure at high potentials.
Screened cables (H-type) use metallized paper screens to maintain a radial electrical field.
The transition voltage for replacing belted cables with screened cables is typically 11 kV.
Belted: Cost-effective for low-voltage distribution.
Screened: Effectively eliminates tangential electric stress.
Screened: Enables higher voltage transmission by maintaining uniform radial stress.
Belted: Prone to insulation breakdown due to non-radial field stress.
Screened: Higher manufacturing cost and increased cable diameter.
Belted: Underground distribution up to 11 kV.
Screened: High-voltage power transmission systems (up to 66 kV).
| Feature | Belted | Screened |
|---|---|---|
Electric Field | Non-radial (Tangential) | Radial |
Max Voltage | Up to 11 kV | Up to 66 kV |
The H-type cable is named after its inventor, Hochstadter.
Option B is correct because belted cables suffer from high tangential electrical stress as voltage levels increase, necessitating the shift to screened cable designs.
B is correct тАФ Belted cables are unsuitable for high voltages because they possess tangential electrical fields which lead to dielectric failure, unlike screened cables which utilize radial fields.
Always remember that for voltages exceeding 11 kV, the presence of metallic screens is mandatory to convert the complex electric field into a purely radial one.