Short Answer:

Substations are classified based on the voltage level they handle, which determines their role in the power system. These classifications help in organizing the system into different stages like transmission, sub-transmission, and distribution. The main voltage-based categories are extra high voltage (EHV) substations, high voltage (HV) substations, medium voltage (MV) substations, and low voltage (LV) substations.

Each type serves a specific purpose—from stepping up voltage for long-distance transmission to stepping it down for safe use by consumers. The classification ensures smooth voltage transformation, efficient power flow, and reliable operation of the electrical grid.

Detailed Explanation:

Classification of substations based on voltage

Introduction

In an electrical power system, electricity flows from generating stations to consumers through various stages of voltage transformation. Substations play a key role in this process by stepping up or stepping down voltage levels using transformers and controlling the flow of power using switches and protective devices.

To manage this effectively, substations are classified into categories based on the voltage level they handle. This classification helps in planning, designing, and managing the power network efficiently. Each voltage category corresponds to a specific function and location in the grid.

1. Extra High Voltage (EHV) Substations

• Voltage Range: Above 220 kV (commonly 400 kV, 765 kV)
• Purpose: Used in the transmission network to carry large amounts of power over long distances.
• Location: Found near large power plants or in major grid transmission corridors.
• Features:
  • Large transformers and circuit breakers
  • Strong insulation systems
  • Advanced protection and control systems
• Importance: Reduces current and losses in long-distance power transmission.

2. High Voltage (HV) Substations

• Voltage Range: From 66 kV to 220 kV
• Purpose: Acts as an interface between EHV transmission and sub-transmission or distribution networks.
• Location: Found at intermediate points in the grid and large industrial areas.
• Features:
  • Step-down transformers
  • Switching devices and protection units
• Importance: Connects major load centers and helps divide power into smaller voltage sections.

3. Medium Voltage (MV) Substations

• Voltage Range: From 11 kV to 66 kV
• Purpose: Used in sub-transmission and distribution networks.
• Location: Near cities, towns, or industrial complexes.
• Features:
  • Distribute power to smaller substations or directly to large consumers
  • Often contain feeders to multiple local areas
• Importance: Ensures regional distribution of power and balances local demands.

4. Low Voltage (LV) Substations

• Voltage Range: Below 11 kV (commonly 415 V or 230 V)
• Purpose: Final stage of power delivery to residential and small commercial users.
• Location: Found in neighborhoods, near houses and shops
• Features:
  • Step-down distribution transformers
  • Simple design, usually pole-mounted or ground-based
• Importance: Ensures safe and reliable power supply to end-users.

Why Voltage-Based Classification Is Important

• Safety: Ensures proper insulation, clearance, and equipment choice for each voltage level
• Efficiency: Reduces losses and supports proper load management
• Design Planning: Helps utility engineers organize the network into levels
• Maintenance: Allows easier fault detection and service area control
• Cost Management: Ensures right equipment is used without overspending on high-voltage systems where not needed

Conclusion

Substations are classified into different types based on the voltage they handle—extra high voltage, high voltage, medium voltage, and low voltage. Each category serves a specific purpose in the power system, from long-distance transmission to local distribution. This voltage-based classification helps in maintaining a reliable, safe, and efficient power network, ensuring that electricity is delivered smoothly from power plants to the final consumer.