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Examoogle • User • info@examoogle.com • EE-2024-8821
Chapter 1 of 12 • Page 1 of 248🔒 Protected PDF • Watermarked
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The reserved generating capacity available for service under emergency conditions which is not kept in operation but in working order is known as
Hot reserve
Cold reserve
Spinning reserve
Firm power
Cold reserve
Cold reserve refers to generating capacity that is available for service but is not currently in operation and requires a significant amount of time to be brought online. This capacity is kept in working order, often in a shut-down state, to act as a long-term backup for power systems during maintenance or unexpected outages.
Cold reserve refers to generating capacity that is available for service but is not currently in operation and requires a significant amount of time to be brought online. This capacity is kept in working order, often in a shut-down state, to act as a long-term backup for power systems during maintenance or unexpected outages.
Rtotal=Pmax−Pdemand — representing the total reserve capacity in a power system.
In power system operations, reserves are classified by their readiness. A cold reserve unit is disconnected from the grid and its boiler/prime mover is usually cold. Bringing it online involves startup procedures such as warming the boiler, pressurizing steam lines, and synchronizing the generator, which can take several hours.
Cold reserve is not synchronized with the grid.
It has the longest startup time among reserve types.
It is cost-effective as it consumes zero fuel while idle.
Essential for reliability planning in grid management.
No fuel consumption during idle periods
Reduces operational wear and tear on auxiliary equipment
Provides long-term security against major plant failures
High response time (cannot meet sudden load spikes)
Requires significant startup energy and time
Higher risk of equipment degradation if not maintained during idle state
Seasonal peak load management
Backup for planned maintenance outages
Long-term contingency planning
| Feature | Spinning Reserve | Cold Reserve |
|---|---|---|
Startup Time | Minutes | Hours |
Grid Sync | Yes | No |
Spinning reserve refers to units connected to the bus and synchronized, ready to pick up load instantly.
Hot reserve refers to units ready to be started but not synchronized, requiring less time than cold reserve.
B is correct — Cold reserve is generating capacity that is kept in working order but is currently idle, requiring a significant warm-up period to supply power.
Always differentiate reserves by 'readiness': Spinning is instant (synchronized), Hot is fast (ready), and Cold is slow (needs startup).