--- title: "Reserve planning and utility interconnection" subject: "Power Plant Design" chapter: 2 key: "semester_8/power_plant_design:reserve-planning-interconnection" source: https://www.bctengineer.com/q/semester_8/power_plant_design/reserve-planning-interconnection site: BCT Engineering --- # Reserve planning and utility interconnection Power Plant Design · Chapter 2: Integrated System Planning in Design Approach - Asked in: 2072 Magh, 8 marks - Answer checked by Claude Opus 5.5 (high effort) on 2026-10-14 - Page: https://www.bctengineer.com/q/semester_8/power_plant_design/reserve-planning-interconnection - Whole chapter: https://www.bctengineer.com/md/semester_8/power_plant_design/chapter-2 ## Question What is Reserve Planning? Study the benefits of interconnection of utilities on power system? ## Short answer Reserve planning decides extra capacity above peak to cover outages, maintenance, forecast errors and low hydrology, using deterministic or probabilistic methods with typical reserve margin 15-25%. Interconnection benefits include reduced reserve, improved reliability, load diversity, economic operation, seasonal exchange, larger units, frequency stability, renewable integration and deferred investment. ## Answer **Reserve planning** is deciding how much generating capacity, above the forecast peak demand, must be kept available (installed or running) so that supply continues reliably despite forced outages of units, planned maintenance, load forecast errors and low hydrology. #### Reserve planning **Types of reserve** | Type | Meaning | Response | |---|---|---| | Spinning reserve | Unloaded capacity of synchronised units | Seconds to minutes | | Non-spinning / standby | Units that can start quickly (hydro, gas turbine, diesel) | ~10–30 min | | Cold / planning reserve | Extra installed capacity for maintenance, growth | Hours to days | **Reserve margin** $$ \text{Reserve margin} = \frac{\text{Installed capacity} - \text{Peak demand}}{\text{Peak demand}} \times 100\% $$ Typical values are 15–25%. **Methods** 1. **Deterministic:** Reserve ≥ largest unit, or a fixed percentage of peak. 2. **Probabilistic:** Using unit forced outage rates to compute LOLP/LOLE; reserve is chosen so that LOLE ≤ e.g. 1 day in 10 years (or 1 day/year). **Factors:** Size of the largest unit, forced outage rates, maintenance schedule, load forecast uncertainty, hydrology (dry-year energy), and availability of interconnection. #### Benefits of interconnection of utilities 1. **Reduced reserve:** Utilities share reserve; total installed reserve is less than the sum of separate reserves. 2. **Improved reliability:** Help from neighbours during outages; fewer blackouts. 3. **Load diversity:** Different peak times reduce combined peak and needed capacity. 4. **Economic operation:** Cheaper plants supply more load across the region; lower fuel cost. 5. **Seasonal exchange:** Nepal exports wet-season surplus and imports in the dry season through Nepal–India lines. 6. **Larger, efficient units** can be installed. 7. **Frequency stability:** More inertia; smaller frequency dips after disturbances. 8. **Renewable integration:** Variability of solar/wind is smoothed across a larger area. 9. **Deferred investment:** New plants can be postponed by importing power. **Drawbacks to manage:** Faults can spread (cascading), higher fault levels, need for tie-line control, protection coordination and commercial agreements. ## Check yourself The answer's key points as multiple-choice questions, with the correct option and why. 1. Reserve planning decides A. the tariff B. how much capacity above forecast peak must be available to keep supply reliable despite outages, maintenance, forecast errors and low hydrology C. the dispatch order only D. line routes Answer: B. Reserve covers forced outages, maintenance, forecast error and dry years. (Key point: Reserve planning) 2. How is reserve margin calculated? A. (Installed - Peak) / Peak x 100% B. Peak / Installed C. Installed / Peak D. (Peak - Installed)/Installed Answer: A. Reserve margin = (installed capacity - peak demand)/peak demand x 100%, typically 15-25%. (Key point: Reserve margin) 3. Which is spinning reserve? A. Extra installed capacity for maintenance B. Unloaded capacity of synchronised units responding in seconds to minutes C. Cold units needing days D. Imported fuel Answer: B. Spinning reserve is headroom on running units. (Key point: Spinning reserve) 4. What does the probabilistic method use? A. Largest unit only B. Fixed percentage of peak C. Unit forced outage rates to compute LOLP/LOLE D. Tariff Answer: C. Reserve is chosen so LOLE stays within a target, using forced outage rates. (Key point: Probabilistic method) ## Related in Power Plant Design - [Power system expansion planning for a utility](https://www.bctengineer.com/question.md?key=semester_8%2Fpower_plant_design%3Aexpansion-planning-national-utility) — Power Plant Design, chapter 2 - [Regional interconnection and reserve bottling](https://www.bctengineer.com/question.md?key=semester_8%2Fpower_plant_design%3Aregional-interconnection-reserve) — Power Plant Design, chapter 2 - [Benefits of interconnecting regional utilities](https://www.bctengineer.com/question.md?key=semester_8%2Fpower_plant_design%3Aregional-interconnection-benefits) — Power Plant Design, chapter 2, asked 2× - [Power system security and reserve requirement](https://www.bctengineer.com/question.md?key=semester_8%2Fpower_plant_design%3Asecurity-reserve-requirement) — Power Plant Design, chapter 2 - [Power system planning and grid integration](https://www.bctengineer.com/question.md?key=semester_8%2Fpower_plant_design%3Aplanning-deregulated-grid-integration) — Power Plant Design, chapter 2 - [Spinning reserve versus reserve power](https://www.bctengineer.com/question.md?key=semester_8%2Fpower_plant_design%3Aspinning-reserve-vs-reserve) — Power Plant Design, chapter 2 ## Related in other subjects - [Benefits and problems of reuse; reuse planning](https://www.bctengineer.com/question.md?key=semester_5%2Fsoftware_engineering%3Areuse-benefits-problems) — Software Engineering, chapter 5 - [Case study: workflow, factors, proposed design, benefits](https://www.bctengineer.com/question.md?key=semester_5%2Finstrumentation_ii%3Acs-2076chaitra) — Instrumentation II, chapter 10 - [Role of interconnection and reactive power control](https://www.bctengineer.com/question.md?key=semester_5%2Fpower_system_analysis_ii%3Ainterconnection-reactive-control) — Power System Analysis II, chapter 1 - [Reactive power compensation and its benefits](https://www.bctengineer.com/question.md?key=semester_4%2Fpower_system_analysis_i%3Areactive-compensation-meaning-benefits) — Power System Analysis I, chapter 6, asked 2×