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Which of the following is used to maintain clearance between ground and live conductor in substations?
Isolators
Insulators
Circuit breakers
All of above
Insulators
Insulators are the mechanical components used to support live conductors while providing necessary electrical insulation to maintain clearance from the grounded structures (such as steel towers, gantries, or poles) of a substation. They possess high dielectric strength to withstand the line voltage and sufficient mechanical strength to endure the weight and tension of the conductors.
Insulators are the mechanical components used to support live conductors while providing necessary electrical insulation to maintain clearance from the grounded structures (such as steel towers, gantries, or poles) of a substation. They possess high dielectric strength to withstand the line voltage and sufficient mechanical strength to endure the weight and tension of the conductors.
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Rinsulation=ρAl
The insulating material (typically porcelain, glass, or polymer) acts as a high-resistance path that prevents current leakage from the live conductor to the grounded support. The clearance distance is determined by the impulse and power-frequency withstand voltage requirements of the specific voltage level, which are provided by the length and profile (sheds) of the insulator string.
Insulators provide both electrical isolation and mechanical support.
The number of discs in a string is proportional to the operating voltage level.
Creepage distance is the shortest path over the insulator surface between metal parts.
Polymer insulators are increasingly used due to their light weight and hydrophobic properties.
High dielectric strength
High mechanical tensile/compressive strength
Resistance to environmental factors like moisture and pollution
Susceptible to surface tracking if heavily polluted
Brittle nature (in the case of porcelain or glass)
Substation busbar support
Transmission line suspension
Isolator/Switchgear support structures
Isolators are switching devices for manual isolation, circuit breakers are for fault interruption, but only insulators provide the structural electrical clearance.
The required clearance is governed by IS 3072:1975 standards for substation design.
B is correct — Insulators are specifically designed to provide electrical isolation and maintain the required clearance between energized conductors and grounded structures.
Always distinguish between 'Switching' devices (Isolators/CBs) and 'Support' devices (Insulators) in power system questions.