--- title: "Sketch of a medium head PROR plant" subject: "Power Plant Design" chapter: 3 key: "semester_8/power_plant_design:pror-medium-head-sketch" source: https://www.bctengineer.com/q/semester_8/power_plant_design/pror-medium-head-sketch site: BCT Engineering --- # Sketch of a medium head PROR plant Power Plant Design · Chapter 3: Hydro Power Plant Design - Asked in: 2081 Chaitra, 8 marks; 2073 Bhadra, 4+4 marks (asked 2 times) - Video: [Components of Hydroelectric Power Plant | Hydroelectric Power Plant | Power Pant | Fluid Mechanics](https://www.youtube.com/watch?v=MSR7Acw_Q6U) — Professor Nidhi Trivedi - Answer checked by Claude Opus 5.5 (high effort) on 2026-10-14 - Page: https://www.bctengineer.com/q/semester_8/power_plant_design/pror-medium-head-sketch - Whole chapter: https://www.bctengineer.com/md/semester_8/power_plant_design/chapter-3 ## Question Make a sketch to show various components of medium head and relatively large discharge, medium size Pondage Run of River (PRoR) hydropower plant. Also, mention the functions of each component. ## Short answer A PRoR plant has a weir forming pondage, intake, desander, headrace, surge tank, penstock, powerhouse with Francis turbines, tailrace, and switchyard. Pondage stores off-peak inflow for daily peaking; surge tank controls water hammer; Francis turbines suit medium head and large discharge. ## Answer A **Pondage Run-of-River (PRoR)** plant diverts river water through a water conductor like an ROR plant, but stores water in a **pondage** (daily storage) during off-peak hours so that the plant can run at full output during the peak hours (typically 4–6 hours in the evening). For medium head (about 50–300 m) and relatively large discharge, **Francis** turbines are used. #### Sketch ```text River | ======[Dam/Weir + Gates]====== | Pondage (daily storage) |---> Spillway |_____________________________| | | | +--> Riparian release [Intake + trash rack] | [Desander / settling basin] | Headrace tunnel ==============\ [Surge tank] | Penstock | \| [Powerhouse: MIV, Francis, Generator, Governor, AVR] | | Tailrace GSU transformer | | River Switchyard -> Grid ``` #### Components and functions | Component | Function | |---|---| | Diversion dam / weir with gates | Raises water level, diverts water, forms pondage | | Pondage | Stores off-peak inflow for daily peaking operation | | Spillway, undersluice | Passes floods, flushes sediment | | Intake with trash rack | Admits design flow; stops debris | | Desander (settling basin) | Removes fine sediment to protect turbines | | Headrace tunnel | Conveys large discharge to the surge tank with low loss | | Surge tank | Controls water hammer; supplies flow during load change | | Penstock / pressure shaft | Carries water under pressure to turbines | | Main inlet valve | Isolates each unit | | Francis turbine + draft tube | Converts hydraulic energy to mechanical; draft tube recovers energy | | Governor | Controls speed/frequency and load | | Synchronous generator + excitation/AVR | Generates power; controls voltage and reactive power | | Generator CB, GSU transformer | Switching and step-up to transmission voltage | | Switchyard | Connects plant to grid; isolation and protection | | Tailrace | Returns water to the river | | Auxiliaries | Station transformer, DC system, diesel generator (black start), cooling, crane, SCADA | #### Why PRoR It supplies the evening peak, which is valuable in Nepal, especially in the dry season (e.g. Kaligandaki A, Middle Marsyangdi are peaking ROR plants). ## Check yourself The answer's key points as multiple-choice questions, with the correct option and why. 1. What distinguishes a Pondage Run-of-River plant? A. It has no storage at all B. It stores off-peak flow in a daily pondage to run at full output for the peak hours C. It has a seasonal reservoir storing monsoon water D. It uses only Pelton turbines Answer: B. PRoR holds daily storage so the plant can generate at full output for 4-6 evening peak hours. (Key point: PRoR concept) 2. The undersluice gates are used to: A. Flush sediment near the intake B. Generate power C. Step up voltage D. Control turbine speed Answer: A. Undersluice gates flush sediment, while the spillway passes floods. (Key point: Spillway and undersluice) 3. The excitation system and AVR of the synchronous generator control: A. Water hammer B. Terminal voltage and reactive power C. Sediment settling D. Penstock pressure Answer: B. The AVR adjusts excitation to control voltage and reactive power. (Key point: Generator and AVR) 4. Why is PRoR valuable in Nepal? A. It supplies the evening peak, especially in the dry season B. It needs no intake C. It stores water for years D. It has no environmental flow Answer: A. Peaking power is valuable, particularly in the dry season, e.g. Kaligandaki A. (Key point: Why PRoR) ## Related in Power Plant Design - [Components of a medium head high discharge plant](https://www.bctengineer.com/question.md?key=semester_8%2Fpower_plant_design%3Amedium-head-high-discharge-components) — Power Plant Design, chapter 3, asked 2× - [Daily pondage run-of-river components](https://www.bctengineer.com/question.md?key=semester_8%2Fpower_plant_design%3Adaily-pondage-ror-components) — Power Plant Design, chapter 3 - [Components of a run-of-river plant](https://www.bctengineer.com/question.md?key=semester_8%2Fpower_plant_design%3Aror-components-functions) — Power Plant Design, chapter 3, asked 2× - [Hydropower plant components and functions](https://www.bctengineer.com/question.md?key=semester_8%2Fpower_plant_design%3Ahydropower-components-functions) — Power Plant Design, chapter 3, asked 2× - [ROR versus PROR hydropower plants](https://www.bctengineer.com/question.md?key=semester_8%2Fpower_plant_design%3Aror-vs-pror) — Power Plant Design, chapter 3 - [Daily pondage ROR with 150 m head](https://www.bctengineer.com/question.md?key=semester_8%2Fpower_plant_design%3Adaily-pondage-150m-head) — Power Plant Design, chapter 3 ## Related in other subjects - [RoR and PRoR from hydrograph equation (Q40)](https://www.bctengineer.com/question.md?key=semester_7%2Fhydropower_engineering%3Aror-pror-hydrograph-equation-q40) — Hydropower Engineering, chapter 3 - [RoR pondage: capacity and pondage volume](https://www.bctengineer.com/question.md?key=semester_7%2Fhydropower_engineering%3Aror-pondage-capacity-load-factor-65) — Hydropower Engineering, chapter 3 - [Pondage surface area and weekly output](https://www.bctengineer.com/question.md?key=semester_7%2Fhydropower_engineering%3Apondage-weekly-operation-40cumec) — Hydropower Engineering, chapter 3 - [Components that make up the Web](https://www.bctengineer.com/question.md?key=semester_7%2Fweb_technology%3Acomponents-of-web) — Web Technology, chapter 2