You must have seen Stones or Gravel spread in the Switchyard if you got the chance to visit any Substation.
Ever wondered why Switchyard Surface is Covered with Gravels? Why Stones are used in Switchyard?
Well, I have explained every possible reason for it. Let’s see.!
Reasons Why We Use Stones/Gravel in Switchyard
There are various benefits of using Stones/Gravel over the PCC (Plain Cement Concrete) in Switchyard. I’ve shared some points for easy understanding. Every point is inter-related with another one. Let’s Learn Why it is used in Electrical Switchyard.
#1 Gravel Increases Resistance between Our Foot & Ground.
Substation Switchyard is already grounded by earth mates to provide a very low resistance path to the fault current to flow to the ground. But, the Stones or Gravels are used in the Switchyard to decrease the Foot Surface Area. When the touch surface area decreases the resistance increases.
So, the main purpose of filling Switchyard with Stones/Gravels is to provide an extra layer of high resistance and act as an insulator between our foot and the ground.
Thus, gravels in Switchyard increases the resistance between our foot and ground.
#2 Gravels Prevent the Accumulation of Rain Water in Switchyard.
Stones/Gravels prevent the accumulation of water over the PCC surface in Switchyard and even if some water accumulates over some part of PCC due to the non-uniform (not fully plain) surface then Gravel provides some breaks over the surface of the water.
It makes the current non-continuous through our body and finally, it increases the resistance.
Finally, the rainwater can drop faster and it doesn’t make any mud inside the Substation.
#3 Gravel Reduces Step Potential & Touch Potential when Operators Work on Switchyard.
Step and Touch potential increases during Short circuit current. Gravel/Stones in Switchyard is provided to reduce the step potential and touch potential when operators work on Switchyard in the Substation.
Step Potential: It is the potential developed between the two feet on the ground of a man or animal when a short circuit occurs. This results in the flow of current in the body lead to electrical shock.
Touch potential: It is the potential that is developed between the ground and the body of the equipment when a person touches the body during fault condition. When the person touches electrical equipment during short circuit condition, fault current flows through the human body. This is defined as a touch potential.
#4 Stone Prevents Vegetation & Growth of Small Weeds, Plants inside the Switchyard:
Do you know? Vegetation is already prevented by PCC and growth of small weeds and plants in the Switchyard is prevented.
But, if we don’t fill with gravels then after some days/months/years, some soils & water will accumulate in many parts on the Switchyard and grass will also grow.
Thus, Gravels prevents the growth of grass & other small plants inside the Switchyard and Substation remains nice & clean.
#5 Prevents the Entry of Animals & Wildlife:
The entry of animals like Rats, Snakes, Lizards, etc. are also prevented to some extent by spreading Gravels over the Switchyard surface.
#6 Improves Yard Working Condition
Gravels also improves the working condition in the Switchyard of a Substation.
#7 Protect from Fire when Oil Spillage Takes Place
In Substation, Power Transformers & Shut Reactors are filled with oil as a cooling and insulating medium. Oil leakage takes place during operation or when changing the oil in the transformer. The spillage oil which can catch fire is dangerous to the switchyard operation. So, Stones/Gravel is provided to protect from fire when oil spillage takes place.
So, these are the benefits of using Stone/Gravel in the Switchyard.
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