Answer / usman aslam

It is placed for human safety. Lightening can cause step
potential between 2 feet of the person standing in yard.
So gravel is placed so that moisture is maintained and
potential of earth remains equal throughout the yard hence
step potential will be zero.

Answer / aaa

It provides a highly resistive layer which increases the allowable step and touch potentials.

Answer / brandon

A thin layer of aggregate above a low-resistance substrate
(or embedded ground grid if the substrate is a
high-resistance material) provides a high resistance between
the bottom of a human's feet and the substrate. This will
lower the upward current through the body considerably in
the event of a L-G fault compared to the equipment bonds
(assuming equipment is properly bonded to the substation
ground). However, since the aggregate is thin relative to
the ground plane, it does not impede the shape of the
equipotential voltage field of the substation and thus
reduces the step potential by keeping a consistant voltage
grading.

Aggregate is not for lightening as lightening protection is
provided through overhead shield conductors bonded to the
ground grid or substrate.

If oil-filled equipment fails and and a fire is started, the
aggregate also has a quenching effect by distributing the
oil within the void spaces and creating small pockets
instead of a large surface of oil.

See IEEE 80 for the complete explanation.

Answer / nikhil

This is done to prevent grass to grow in the area. Grass
can cause dew or moisture which can be dangerous for the
equipments and working staff there.

Answer / sukhvinder

Gravelling is done to reduce the ground resistance of the
foot from its value.

Answer / yogendra singh

This is done to prevent grass to grow in the area. Grass
can cause dew or moisture which can be dangerous for the
equipments and working staff there

Answer / dinesh

its placed to avoid the soil erosion from the substation in
rainy season & also to prevent grass & unwanted plant to
grow in the substation which can harm the equipments.
Such unwanted plants & greenery can be home for reptiles
which cam cause short-circuit etc to the equipments and
also damage.

Answer / samal

Ok grass can cause moisture ,it will help in maintaining
the resistance of yard(will be very low)

so moisture is not the reason of that cause.
it(aggregate) will mantain the capacitance of yard ground
to live part & helps in maintaining vibration

Answer / alpz

its because majority, if not all of equipment in substation
is oil filled, aggregate is use to prevent oil in dripping
around the entire s/s in case there's a maintenance or
accidental leak in any equipment.

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