Short Answer:

The function of spinning reserve in power systems is to provide immediate backup power in case of sudden generation loss or unexpected increase in load. It is the extra generation capacity that is already running and synchronized with the grid but not fully loaded, so it can quickly respond when needed.

Spinning reserve helps maintain system frequency stability, prevents blackouts, and ensures continuous power supply during emergencies. It is one of the key components of system reliability and is maintained by keeping some generators operating below their maximum output level.

Detailed Explanation:

Function of spinning reserve in power systems

Spinning reserve plays a vital role in the reliable and stable operation of an electrical power system. It refers to the portion of online but unloaded generating capacity that can be quickly ramped up to respond to sudden disturbances such as generator outages, transmission failures, or unexpected demand surges. This reserve is “spinning” because the generators are already operating and connected to the grid but are held in readiness to supply power instantly when needed.

In large interconnected grids, maintaining spinning reserve is essential to prevent frequency deviations, support system recovery, and ensure continuous power delivery during unplanned events. Spinning reserve is one of the types of operating reserves, which also include non-spinning and supplemental reserves.

Key Functions of Spinning Reserve:

1. Immediate Power Support:
   When a major generator trips or a sudden load spike occurs, spinning reserve steps in within seconds to supply the missing power and stabilize the system.
2. Frequency Control:
   Frequency drops when there is a sudden generation loss. Spinning reserve provides quick power to arrest frequency decline and bring it back to normal levels (e.g., 50 Hz).
3. Enhances System Reliability:
   By maintaining spinning reserve, the power system ensures backup support at all times, improving reliability during emergencies or peak demands.
4. Supports Automatic Generation Control (AGC):
   Spinning reserve units are often controlled by AGC systems to automatically adjust their output in response to changes in system frequency or area control error (ACE).
5. Maintains Load-Generation Balance:
   It ensures that the system can maintain a balance between generation and demand even during faults or operational uncertainties.

Characteristics of Spinning Reserve:

• Synchronized with the Grid:
  It is already running and in phase with the power system.
• Fast Response Time:
  Can be activated within seconds to a few minutes after a disturbance.
• Partial Load Operation:
  The generator operates below its rated capacity so that it can quickly ramp up output when required.
• Automatically or Manually Activated:
  Some spinning reserves are activated automatically through control systems, while others may be manually dispatched.

Importance in Modern Power Systems:

• As more renewable energy sources like solar and wind are integrated, spinning reserve becomes even more important due to the variable nature of these sources.
• It provides operational flexibility and supports grid stability in both normal and emergency situations.
• Regulatory bodies often define minimum spinning reserve requirements to ensure grid security.

Conclusion:

The function of spinning reserve in power systems is to provide a quick-response backup to maintain system stability and prevent blackouts during sudden disturbances. It ensures that power generation can be instantly increased to match load demand when unexpected events occur. As a key part of operational reserves, spinning reserve plays a critical role in frequency control, reliability, and grid resilience.