Why Stones Are Used in Electrical Substations?

Why Stones Are Used in Electrical Substations

In electrical substations, a thick layer of crushed stones or gravel is spread across the ground surface primarily for safety and operational efficiency. The main reason is to enhance electrical insulation and prevent the dangerous effects of step potential and touch potential. When there is a fault or leakage in the system, electricity may escape into the ground. If the ground is wet or made of conductive soil, it can allow current to flow through a person's body standing nearby. Stones, being poor conductors of electricity, act as an insulating barrier that limits current flow through the body in such cases, reducing the risk of electric shock or electrocution.

Additionally, the stone bed improves drainage and keeps the surface dry, which further enhances insulation and minimizes the chance of ground faults. It also suppresses the growth of weeds and vegetation, which could otherwise interfere with equipment or become a fire hazard. Moreover, the gravel layer helps reduce dust and mud, creating a cleaner and more stable environment for the substation equipment and maintenance personnel. It also provides a firm foundation for walking and movement, improving both safety and accessibility.

They act as a non-conductive layer, reducing the risk of electric shock by minimizing step and touch potentials during fault conditions. Additionally, they help prevent the growth of vegetation, absorb spilled oil, and improve drainage, contributing to a safer and more easily maintained environment. 

Here's a more detailed breakdown:

Safety:

Step and Touch Potential Reduction:

During ground faults, electricity can flow through the ground, creating voltage differences between points where a person might be standing or touching equipment. Stones, with their higher resistivity compared to soil, help limit the current flow through a person's body, reducing the severity of potential shocks. 

Insulation:

The layer of stones acts as an additional layer of insulation between the ground and equipment, further minimizing the risk of electrical hazards. 

Fire Prevention:

In case of oil leaks from transformers, the stones can help absorb the spilled oil, preventing it from spreading and creating a fire hazard. 

Maintenance:

Vegetation Control:

Stones inhibit the growth of grass, weeds, and other plants, reducing the need for regular vegetation management and preventing potential interference with equipment or personnel. 

Drainage:

The porous nature of gravel allows for good drainage, preventing the accumulation of water and reducing the risk of corrosion or other issues associated with moisture. 

Accessibility:

The presence of stones provides a relatively clean and stable surface for workers to walk on, improving accessibility for maintenance and inspections. 

Heat Dissipation:

Stones can also help with heat dissipation from transformers, further contributing to a stable operating environment, according to a voltage lab article.

Summary:

Crushed stones in substations are used mainly for electrical insulation, safety, and ground fault protection. They reduce the risk of electric shock by limiting step and touch potentials, help with drainage, suppress vegetation growth, and maintain a clean, stable, and safe working surface.