WHY STONES ARE LAID IN A SWITCHYARD

 WHY STONES ARE LAID IN A SWITCHYARD

Wonderful discussion with Shri SKB Valli during skill development training.

Very few understand the reason.

📌Those stones are not random, and they are not all the same.

📌They are a designed safety layer in high-voltage environments.

1. They Control Step and Touch Voltage.

When a fault occurs, large current flows into the earth.

The crushed stones:

▫️Increase surface resistance

▫️Reduce voltage difference between a person’s feet

▫️Lower the chance of current passing through the body.

This is the primary reason stones are used.

2. They Work With the Earthing System.

Under the stones is a buried earthing grid.

The stones:

▫️Sit above the earth mat

▫️Limit surface current flow

▫️Make the earthing system more effective

▫️Without stones, the earthing grid alone is not enough.

3. The Stones Are Specially Selected.

Not every stone is acceptable.

Switchyards use:

▫️Crushed gravel, not smooth stones

▫️Specific size range

▫️High resistivity material

▫️Clean, dust-free stones

Smooth or small stones defeat the purpose.

4. They Reduce Moisture and Surface Conductivity.

Wet soil conducts electricity easily.

Gravel:

▫️Drains water quickly

▫️Prevents pooling

▫️Keeps surface resistance high

Dry surface equals safer switchyard.

5. They Help Control Fire and Oil Spills.

Many substation equipment are oil-filled.

The stones:

▫️Absorb and spread leaked oil

▫️Reduce flame propagation

▫️Improve fire safety around transformers.

6. They Improve Operational Safety.

Stones:

▫️Prevent slippery surfaces

▫️Make leaks and faults visible

▫️Protect personnel during movement and maintenance.

A Common Wrong Assumption

❌ “The stones are just for drainage.”

Drainage helps, but electrical safety is the real purpose.

THE REAL TRUTH

Switchyard stones are not decoration.

They are not optional.

They are engineered safety material.

Remove them, and the switchyard becomes electrically dangerous.

Start safe. Work safe. Finish safe.

#ElectricalSafety

#Switchyard

#SubstationLife

#EarthingSystem

#HighVoltage