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Which of the following insulation material is/are generally used in transmission and distribution lines?
Porcelain
Glass
Stelite
All of these
All of these
Transmission and distribution lines utilize insulators made from materials with high dielectric strength and mechanical properties to prevent leakage current. Porcelain, toughened glass, and composite/polymer materials (like Stelite/silicone) are standard industry choices.
Transmission and distribution lines utilize insulators made from materials with high dielectric strength and mechanical properties to prevent leakage current. Porcelain, toughened glass, and composite/polymer materials (like Stelite/silicone) are standard industry choices.
R=╧БAlтАЛ тАФ Relation defining insulation resistance where ╧Б is resistivity
E=dVтАЛ тАФ Electric field stress across insulator thickness d
Insulators act as a high-resistance barrier between the current-carrying conductor and the grounded support structure. They must possess high insulation resistance, high mechanical strength to withstand wind and ice loads, and a low coefficient of thermal expansion to survive extreme temperature fluctuations.
Porcelain (Aluminum Silicate) is the most traditional insulator material due to its chemical stability.
Toughened glass provides superior visibility for inspection and is less prone to puncture during surges.
Composite insulators (polymer-based) are increasingly used due to their light weight and hydrophobicity.
Stelite is often used in specialized high-temperature or wear-resistant industrial applications.
High dielectric strength prevents flashovers
Excellent resistance to environmental degradation
High mechanical toughness for long-span support
Ceramic insulators are brittle and heavy
Glass can shatter under extreme mechanical impact
Polymer insulators may suffer from tracking over long periods
Suspension and pin-type insulators for HV transmission lines
Station post insulators for substations
Shackle insulators for low-voltage distribution
Porcelain insulators generally have a dielectric strength of approximately 15-20 kV/mm.
Glass insulators offer the unique advantage of showing 'shattering' if damaged, aiding visual maintenance inspection.
D is correct тАФ Porcelain, glass, and specialized materials like Stelite are all employed in high-voltage engineering for insulation purposes.
Always remember that in high-voltage power systems, the choice of insulator depends not just on voltage levels, but also on the local environmental pollution levels (Creepage distance requirement).