What are load shedding techniques used in grid management?

Short Answer:

Load shedding techniques are used in grid management to reduce the load on the power system when demand is higher than supply. It helps prevent grid failure, voltage drop, or a complete blackout. In this method, electricity supply is temporarily turned off in selected areas to balance the system.

Different techniques include manual load shedding, automatic load shedding, rotational (scheduled) load shedding, under-frequency load shedding, and demand response-based shedding. These methods help maintain grid stability, protect equipment, and ensure that essential services continue to receive electricity during high-demand or emergency situations.

Detailed Explanation:

Load shedding techniques used in grid management

In electrical power systems, it is very important that the generation and demand remain balanced at all times. When the demand becomes too high or there is a sudden drop in power generation due to faults, weather, or equipment failure, the grid can become unstable. If not controlled quickly, this can lead to blackouts or voltage collapse. To avoid this, grid operators use a method called load shedding.

Load shedding means intentionally cutting off electricity supply to certain parts of the grid to reduce the overall load and restore balance. This action is taken as a last resort to protect the rest of the grid and ensure power continues to flow to critical areas like hospitals, water treatment plants, and emergency services.

Different load shedding techniques are used depending on the severity of the problem, the system’s capacity, and the available control infrastructure.

  1. Manual Load Shedding

This is the simplest and most traditional method. The operator manually decides which areas or feeders to disconnect based on priority and demand levels.

  • Used when automatic systems fail
  • Usually pre-planned and based on a load shedding schedule
  • Takes time and coordination

Example: Disconnection of specific feeders or substations using breakers operated manually.

  1. Automatic Load Shedding

This system uses relays and sensors to automatically detect abnormal conditions such as:

  • Overloading
  • Low frequency
  • Voltage drops

When such events are detected, pre-programmed breakers are tripped automatically to shed load without human intervention.

Benefits:

  • Fast and efficient
  • Avoids full grid collapse
  • Reduces stress on operators
  1. Rotational or Scheduled Load Shedding

In this method, areas are disconnected in turns for a fixed period (like 1 or 2 hours) based on a time table.

  • Reduces inconvenience to consumers
  • Keeps the system fair and manageable
  • Especially useful during power shortages

Example: Each area gets power cut for 2 hours once a day based on a published schedule.

  1. Under-Frequency Load Shedding (UFLS)

This is a protective method where loads are disconnected automatically when the frequency drops below a safe limit (e.g., below 49.5 Hz in India).

  • Triggered by sudden generation loss
  • Prevents system-wide blackout
  • Critical for fast response in emergencies

Relays installed at key points trip loads in stages depending on how low the frequency falls.

  1. Demand Response-Based Shedding

In smart grids, some consumers (mainly industries) agree to reduce their load during peak times in exchange for benefits like lower tariffs.

  • Controlled through AMI and communication systems
  • Can be voluntary or contract-based
  • Helps reduce load without power cuts

Example: Turning off industrial processes or delaying air conditioning usage during peak hours.

  1. Priority-Based Load Shedding

Loads are classified into critical, important, and non-essential. Non-essential loads are shed first to ensure critical loads stay connected.

  • Used in hospitals, airports, and data centers
  • Supports uninterrupted service to high-priority zones

Why Load Shedding Is Necessary

  • Prevents grid collapse during emergencies
  • Helps maintain voltage and frequency stability
  • Protects equipment from damage due to overload
  • Allows time for system recovery or generator start-up

How It’s Managed

  • Grid operators use SCADA systems to monitor and control loads
  • Real-time data helps decide how much load needs to be shed
  • Load shedding plans are prepared and approved in advance for emergency use
Conclusion

Load shedding is an important tool used in grid management to protect the power system from failure during times of high demand or low generation. Techniques like manual shedding, automatic relays, under-frequency protection, and demand response help balance the load quickly and safely. Properly designed load shedding strategies ensure stable power supply, reduce inconvenience, and protect both consumers and equipment from unexpected failures.