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Power system security and reserve requirement

Short answer

Power system security is the ability to withstand sudden disturbances and continue supplying load, usually meeting the N-1 criterion. Reserve is capacity above peak demand, comprising spinning, non-spinning, and planning reserves; the reserve margin is typically 15-25%.

What is power system security? Also describe about reserve requirement in a power system.

Power system security is the ability of the power system to withstand sudden disturbances such as loss of a generator, line or transformer, or a short circuit, and continue supplying load without violating voltage, frequency and loading limits. The usual criterion is N-1: the system must remain secure after any single outage.

Reserve requirement

Reserve is the generating capacity kept above the forecast peak demand.

  • Spinning reserve: unloaded capacity of synchronised units; at least equal to the largest running unit, for sudden outages and frequency control.
  • Non-spinning (standby) reserve: quick-start units (hydro, gas turbine, diesel) that can come on line within 10–30 minutes.
  • Planning (cold) reserve: extra installed capacity for maintenance, forced outages, load growth and dry-year hydrology.

Reserve margin

RM=Pinstalled−PpeakPpeak×100%RM = \frac{P_{installed} - P_{peak}}{P_{peak}} \times 100\%

Typical values are 15–25%. It is fixed either deterministically (largest unit, fixed %) or probabilistically (LOLP/LOLE target). Interconnection with neighbouring grids reduces the reserve requirement.

✓ Answer checked by Claude Opus 5.5 (high effort)

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