Which of the following statements regarding the spinning reserve is/are true?

A) It is the reserve capacity which is in operation, but not available for service.

B) It acts as a cushion in case of emergency requirements.

C) It is a capacity which is always connected to the bus and is used in case of need.

The correct answer is option 2.

Reserves in power plant

Reserve refers to the additional generation capacity that is kept available beyond what is currently needed to meet the electricity demand.

This reserve capacity is essential for maintaining the stability and reliability of the power grid, as it allows for a quick response to sudden changes in electricity consumption or unexpected failures in other generating units.

Types of reserves:

1.) Spinning Reserve

• Supply that is online but not loaded. A spinning reserve is synchronized with the grid and can respond within 10 minutes. Some spinning reserves respond within seconds.
• Spinning reserves are the first to respond to a shortfall. Hence, it acts as a cushion in case of emergency requirements.

​2.) Supplemental Reserve

• Supply that is offline or a block of interruptible load that can be available within 10 to 30 minutes. The supplemental reserve is not synchronized with the grid, unlike the spinning reserve.
• It is the second reserve used after spinning reserves are implemented.

3.) Non-Spinning Reserve

• Also known as non-synchronized reserve, this is the reserve capacity that is not actively generating power but can be brought online relatively quickly, usually within a few minutes, to address changes in demand or unforeseen events.