Why Are Stones Laid in a Switchyard?
If you have a blog about electricity this is an useful topic to talk about when it comes to substation design and safety standards.
1. What Is a Switchyard?
A switchyard is a part of the power system where they install high-voltage equipment like circuit breakers, transformers, isolators and busbars to control and distribute electricity. You can usually find switchyards in power plants and substations
2. Main Reasons Stones Are Laid in a Switchyard
1️⃣ To Reduce Step and Touch Voltage
This is the reason they use stones in a switchyard. When something goes wrong like a circuit or a lightning strike a lot of electricity flows into the ground. This creates a difference in voltage on the surface of the earth which is called step voltage and touch voltage. Step voltage is the voltage difference between a persons two feet and touch voltage is the voltage between a persons hand and feet.
The crushed stones have electrical resistance. So when you stand on the stones of the bare ground the current that flows through your body is reduced and that reduces the risk of getting an electric shock. This makes the switchyard a safer place.
2️⃣ To Improve Grounding Safety
Under the stones there is a grounding grid made of copper or GI conductors buried in the soil. The stones help increase the surface resistance, which helps the current dissipate properly and that supports the effectiveness of the grounding system. This makes the switchyard safer when something goes wrong.
3️⃣ To Prevent Weed and Plant Growth
The switchyard needs to be kept clean and clear. If grass or plants grow they increase the moisture reduce the insulation and create maintenance problems. The thick layer of stones prevents plants from growing. Keeps the area clean.
4️⃣ To Avoid Water Accumulation
The stones help with drainage. When it rains the water passes through the gravel easily. There is no water logging and the equipment foundations stay safe. It is dangerous to have standing water in a high-voltage yard so good drainage is really important.
5️⃣ Fire Protection
If there is a leak of oil or a spark the stones help reduce the spread of fire. They do not. They keep the oil from coming into direct contact with the flame. This adds a layer of fire safety.
6️⃣ To Reduce Dust and Mud
Without the stones the soil would become muddy when it rains and there would be dust when it is dry. The equipment would get dirty. The gravel keeps the area stable and clean.
3. Why Crushed Stones (Not Smooth Stones)?
They use crushed stones of smooth stones because the crushed stones interlock properly they do not move easily and they provide better surface resistance. They also give the ground stability. The stones they usually use in switchyards are 25mm to 50mm in size.
4. Standard Thickness of Stones
Usually they put a 100 mm to 150 mm layer of gravel in the switchyard. In high-voltage substations they might make the layer thicker for safety. The exact thickness they need depends on the voltage level and the design standards.
The stones in a switchyard are not, for decoration. They are a part of the electrical safety system. The stones reduce the risk of shock improve the grounding prevent weeds provide drainage and improve fire safety. So time you see gravel in a substation remember that it is a carefully designed safety feature, not just something they put there for construction. The stones are a part of the safety, protection and maintenance of the electrical system, which is the electrical safety system.
