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The material commonly used for insulation in high voltage cables is
Rubber
Paper
Lead
Any of the above
Paper
Impregnated paper is the standard insulating material for high voltage power cables due to its excellent dielectric strength, high thermal stability, and long-term reliability under continuous electrical stress. When impregnated with high-grade mineral oil or synthetic fluids, it minimizes the formation of voids, which prevents partial discharge and dielectric breakdown.
Impregnated paper is the standard insulating material for high voltage power cables due to its excellent dielectric strength, high thermal stability, and long-term reliability under continuous electrical stress. When impregnated with high-grade mineral oil or synthetic fluids, it minimizes the formation of voids, which prevents partial discharge and dielectric breakdown.
EmaxтАЛ=rln(rRтАЛ)VтАЛ тАФ Electric stress at the conductor surface
C=ln(rRтАЛ)2╧А╧╡0тАЛ╧╡rтАЛLтАЛ тАФ Capacitance of a single-core cable
The insulation system in high-voltage cables works by controlling the electric field intensity, denoted as E=rln(R/r)VтАЛ, where V is the voltage, r is the conductor radius, and R is the insulation radius. High-quality paper insulation provides a high dielectric strength (epsilonrтАЛ) and uniform flux distribution. Impregnation under vacuum ensures the removal of air bubbles, effectively reducing the internal partial discharge inception voltage.
Impregnated paper maintains stable dielectric properties at high temperatures.
The process involves vacuum drying and oil impregnation to eliminate moisture and air gaps.
Mass-impregnated cables are typically used for underground transmission up to 33kV.
Paper insulation exhibits a very low power factor, reducing energy losses as heat.
High dielectric strength per unit thickness
Excellent long-term thermal stability
Low dielectric loss factor
Hygroscopic nature (absorbs moisture easily)
Rigidity compared to cross-linked polyethylene (XLPE)
Requires complex manufacturing involving vacuum and oil processing
Underground transmission lines
High-voltage substations
Submarine power cables
Lead is used as a protective sheath to prevent moisture entry, not as the primary electrical insulation.
Rubber is generally limited to lower voltage applications because it degrades rapidly under high thermal stress and electrical discharge.
Modern alternatives like XLPE (Cross-linked Polyethylene) are now common, but paper remains a fundamental high-voltage reference.
B is correct тАФ Impregnated paper is the traditional, highly reliable insulation material for high-voltage power cables due to its high dielectric integrity.
Always remember that while Paper is the classic answer for high-voltage, XLPE is the modern standard; in competitive exams, prioritize the historical 'Impregnated Paper' for high voltage cable classification questions.