- 2079 Chaitra · 4 marks
Spinning reserve versus reserve power
Short answer
Spinning reserve is unused capacity of synchronised running units, available in seconds to minutes, sized at least largest running unit. Reserve power is total spare capacity above peak, including spinning, non-spinning and cold reserve, typically 15-25% of peak. Spinning reserve is part of total reserve.
What is the difference between spinning reserve and reserve power?
Spinning reserve is the unused capacity of generators that are already running and synchronised to the grid, ready to pick up load within seconds to minutes. Reserve power (total reserve) is all the capacity available above the peak demand, including spinning, non-spinning (quick start) and cold reserve.
Difference
| Point | Spinning reserve | Reserve power (total reserve) |
|---|---|---|
| Meaning | Unloaded capacity of synchronised units | Total spare capacity over peak demand |
| State of units | Running and connected | Running, standby or shut down |
| Response time | Seconds to ~10 min | Seconds to hours/days |
| Purpose | Cover sudden loss of a unit, load jumps; frequency control | Cover outages, maintenance, forecast error, low hydrology |
| Size | Usually ≥ largest running unit | Usually 15–25% of peak (reserve margin) |
| Cost | Higher (units run part-loaded) | Mainly capital cost of extra plants |
| Planning horizon | Operational (daily) | Long-term planning |
Example: A 1,000 MW system with 1,200 MW installed has 200 MW reserve. If units on line can deliver 1,080 MW while load is 1,000 MW, spinning reserve is 80 MW; the remaining 120 MW is non-spinning/cold reserve.
✓ Answer checked by Claude Opus 5.5 (high effort)
Related questions
- Define spinning reserve · Power Plant Design, chapter 2
- Define reserve power · Power Plant Design, chapter 2
- Power system security and reserve requirement · Power Plant Design, chapter 2
- Regional interconnection and reserve bottling · Power Plant Design, chapter 2
- Reserve planning and utility interconnection · Power Plant Design, chapter 2
- Thermal versus nuclear power plant · Power Plant Design, chapter 1 · asked 2×
- Reserve versus resource · Engineering Geology II, chapter 7 · asked 3×
- RMS, phase difference and power from v and i · Basic Electrical Engineering, chapter 5
- Potential difference versus emf · Basic Electrical Engineering, chapter 1
- Aggregate reserve: sandstone N42W/34, 80 m · Engineering Geology II, chapter 7 · asked 2×