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Stones are provided in the substation
To avoid fire accident by draining oil from transformer if leaks
To avoid growing of weeds and plants
To provide insulation
All of above
To avoid fire accident by draining oil from transformer if leaks
Spreading crushed stones (gravel) in a substation yard is a multi-purpose safety measure. It serves to improve electrical safety, fire management, and vegetation control within the critical electrical installation area.
Spreading crushed stones (gravel) in a substation yard is a multi-purpose safety measure. It serves to improve electrical safety, fire management, and vegetation control within the critical electrical installation area.
VstepтАЛ=IfтАЛтЛЕRsurfaceтАЛ тАФ where high surface resistance (RsurfaceтАЛ) limits the step potential during a fault.
The layer of stones increases the electrical resistance of the ground surface, reducing the step and touch potential for personnel during a ground fault. Additionally, the stones facilitate drainage of leaking transformer oil into the underlying oil sump/soak pit, preventing fire spread, and create a barren surface that inhibits weed growth, which could otherwise pose fire hazards and physical obstruction.
High resistivity of stones reduces step and touch potentials significantly.
Provides an effective drainage path for oil to prevent pool fires.
Eliminates the need for chemical herbicides by preventing photosynthesis for weeds.
Stones provide mechanical support for maintenance equipment and heavy cabling.
Improved life safety for operators.
Reduced maintenance costs related to vegetation control.
Enhanced fire safety and containment.
Increased installation labor and material cost.
Potential for uneven surfaces if not properly leveled.
May require periodic cleaning to prevent dust buildup from reducing resistivity.
Outdoor Substations
Transformer yards
Switchgear enclosures
The typical recommended depth for crushed stone in a substation is 100 mm to 150 mm.
Option A is correct: By keeping the transformer site clear of vegetation and creating a drainage path, oil spills are directed to fire-resistant gravel pits.
Option B is correct: A thick layer of stone prevents sunlight reaching soil, effectively stopping weed photosynthesis.
Option C is correct: Stone provides high contact resistance, which acts as supplemental insulation for ground surfaces.
D is correct тАФ The layer of crushed stone in a substation provides multi-faceted benefits, including personnel safety through high electrical resistance, fire hazard mitigation via oil drainage, and maintenance reduction by suppressing vegetation growth.
Always remember that in power systems, grounding is not just about connecting to earth; it is fundamentally about managing potential gradients to keep human operators safe.