Lusaka Business and Technical College | Open Distance
and Flexible Learning Unit
Lesson : Stones in the Switchyard
Programme Electrical Engineering
Subject
Protection Systems
Intake
Instructor
D. Noyoo 0973575238
Stones are laid in switchyards primarily for safety and operational
reasons. They help
 prevent fires from oil spills,
 reduce the risk of electric shock by minimizing step and touch
potentials, and
 improve drainage to prevent water accumulation.
 They also limit vegetation growth that could interfere with
equipment and personnel.
 It restricts the entry of snakes and other reptiles as the
surface would be inconvenient to crawl.
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
Fire Prevention:
Substations often contain large transformers that use oil for insulation and
cooling. Oil leaks can pose a fire hazard. Stones, particularly crushed rock or
gravel, help absorb spilled oil, preventing it from pooling and creating a fire
hazard.

Reduced Electrical Hazards:
During fault conditions (like short circuits), dangerous step and touch potentials
can develop. These potentials are voltage differences that can cause electric
shock if a person comes into contact with them. Stones, being poor conductors
of electricity, help increase the resistance between the ground and a person's
feet or body, reducing the likelihood of a dangerous current flow.

Improved Drainage:
Stones facilitate drainage, preventing water from accumulating around
equipment and personnel. This is important for preventing corrosion and
ensuring safe working conditions.

Vegetation Control:
Stones inhibit the growth of vegetation, which can interfere with equipment and
create tripping hazards. This also helps to maintain a clear working space within
the switchyard.

Enhanced Working Conditions:
By reducing fire hazards, electrical risks, and preventing vegetation growth,
stones create a safer and more manageable working environment for substation
personnel.
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