Why Stones are Used in Substation

Why Stones are Used in Substation
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Transformers and switchyards are critical components of the electrical power distribution network. Why Stones are Used in Substation ? Their design and maintenance are vital for the overall system’s reliability and safety. One intriguing aspect that often catches the eye is the extensive use of stones in these facilities. Let’s delve into the reasons why stones are such an integral part of transformer yards and switchyards.

Reasons behind using stone in substations

1. Barrier for Reptiles

Barrier for Reptiles in substations

Substations face a unique challenge – the presence of reptiles like lizards, chameleons, rats, and snakes. These creatures find it difficult to move on rocks, acting as a natural deterrent, preventing them from penetrating substations easily.

2. Protection from Rainwater

Protection from Rainwater in substation

The conductivity of electricity is a critical concern, especially when rainwater is involved. Acid rainwater, in particular, can disrupt the direct connection of water with the substation. The use of stone creates a barrier, significantly increasing resistance and reducing electrical conductivity.

3. Fire Prevention caused by Pyranol oil leakage

Fire Prevention caused by Pyrinol oil leakage

One potential hazard in substations is the risk of fire, particularly when transformers become overloaded. Pyrinol oil is commonly used for cooling these transformers, and in case of leakage, there’s a risk of fire. Stones play a crucial role in preventing the oil from seeping too far, minimizing the risk of a catastrophic fire.

4. Protection against Step and Touch Potentials

Step and touch potentials are familiar terms for those working in substations. Ignorance of these technical aspects can lead to accidents, and in extreme cases, even death. Stones act as a protective layer, preventing individuals from becoming victims of electric shocks caused by grounding or earthing faults.

5. Transformers Conundrum

Transformers in substations, often rated at high power, generate substantial heat when overloaded. The cooling process involves the use of oil, particularly pyranol oil. Stones serve a dual purpose here – preventing oil seepage and acting as a barrier against potential fire outbreaks.

6. Avoiding Step and Touch Potentials

Understanding the danger of step and touch potentials is crucial for those working in or around substations. The recommended method for protection is to “jump like a rabbit,” moving out of the electrified range without touching any equipment. Awareness and swift action can be a lifesaver in these situations.

7. Grass Cannot Grow on Rocks

The strategic use of stones in substations leads to a dry environment, inhibiting the growth of grass and weeds. This not only prevents aesthetic issues but also contributes to maintaining a safe and controlled environment within the substation premises.

8. Cosmetic Purposes

Aside from their many functional benefits, stones can also be used for their aesthetic appeal. A well-designed transformer yard or switchyard with a neat stone ground cover can present a more organized and professional appearance.

Substation gravel specification

Specification Considerations for Choosing the proper gravel:

  • Stone type: Crushed granite, limestone, or other hard, non-porous stones are preferred due to their high electrical resistivity and drainage properties.
  • Stone size: Typically, a gradation of sizes ranging from 3/4 inch to 1 inch is recommended for optimal packing and drainage. Substation gravel size
Typical Stones Used in Transformer and Switchyards
Stone TypeSize RangeCrushing StrengthOther Characteristics
Crushed Granite12mm – 75mmHighGood drainage, heat resistant
River Pebbles20mm – 100mmMediumNatural appearance, smooth edges
Limestone10mm – 80mmMediumExcellent for compacting, less expensive
  • Thickness: The required thickness depends on the substation voltage level, soil conditions, and local regulations. Generally, a minimum of 3 inches to 6 inches is recommended.
  • Cleanliness: The gravel or stone should be free of dirt, debris, and organic matter to maintain its electrical resistivity and drainage capabilities.
Substation gravel specification


Why Are Stones Used In Transformer Yards?

Stones in transformer yards ensure proper drainage, reducing soil moisture that could cause equipment corrosion and grounding issues.

What Purpose Do Stones Serve In Switchyards?

Stones in switchyards enhance safety by providing a fire-resistant, stable platform, and help maintain equipment grounding.

How Do Stones Improve Grounding In Yards?

Stones reduce soil resistivity, thereby enhancing the grounding system’s effectiveness, which is crucial for operational safety.

Can Stones Prevent Weed Growth In Yards?

Yes, stones can significantly hinder weed growth, maintaining clear areas for safe equipment operation and maintenance.


The use of stones in transformer yards and switchyards goes beyond mere functionality; it is a critical safety feature that helps in the maintenance of the facility while also providing environmental and cosmetic advantages. When planning the construction of such yards, the choice of stone material, size, and quality should be carefully considered to ensure the best possible outcome.


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