--- title: "Parameters for powerhouse dimensions" subject: "Hydro Power" chapter: 5 key: "semester_6/hydro_power:powerhouse-dimensions" source: https://www.bctengineer.com/q/semester_6/hydro_power/powerhouse-dimensions site: BCT Engineering --- # Parameters for powerhouse dimensions Hydro Power · Chapter 5: Components of Hydropower System - Asked in: 2080 Chaitra, 4 marks; 2070 Bhadra, 3 marks (asked 2 times) - Answer checked by Claude Opus 5.5 (high effort) on 2026-10-14 - Page: https://www.bctengineer.com/q/semester_6/hydro_power/powerhouse-dimensions - Whole chapter: https://www.bctengineer.com/md/semester_6/hydro_power/chapter-5 ## Question What parameters do you consider while fixing the dimensions of a power house in a hydel plant? Discuss with plan diagram. ## Short answer Dimension parameters: unit type, size, and number determine length with unit spacing and erection bay; width depends on spiral casing/draft tube and crane span; height is set by turbine setting depth, draft tube, and crane lift clearance. Tailwater flood level and auxiliary space also influence dimensions. ## Answer A **powerhouse** houses the turbines, generators, control and auxiliary equipment. Its plan dimensions and height are fixed mainly by the size and number of generating units. #### Parameters for fixing the dimensions 1. **Number, type and size of units:** turbine type (Pelton, Francis, Kaplan), runner diameter, spiral casing size and generator diameter. 2. **Length:** - Unit spacing (centre to centre) = larger of spiral casing width or generator barrel diameter + clearance (about 1–2 m each side). For Pelton units, the distributor/manifold size governs. - Total length = number of units × unit spacing + **erection (service) bay** (about 1–1.5 unit spacing) + control/auxiliary room. 3. **Width:** governed by spiral casing and draft tube (Francis/Kaplan) or by turbine housing; plus space for main inlet valve, walkways, cable ducts and the overhead crane span. 4. **Height:** - **Setting level** of turbine from cavitation (Thoma σ) and tailwater level. - Draft tube depth below the runner (substructure). - Generator floor, and crane clearance high enough to lift the largest part (generator rotor) over other units. 5. **Crane capacity and span** (heaviest piece to lift). 6. **Tailwater level and flood level:** powerhouse floor above maximum flood; draft tube outlet submerged. 7. **Auxiliaries:** governors, control room, battery room, cooling water, transformers and switchyard space. 8. **Site conditions:** foundation geology, access road, space available (surface or underground). #### Typical plan (Francis units) ```text <-- erection --><-- unit --><-- unit --> bay bay 1 bay 2 +---------------+-----------+-----------+-----+ | | ( G1 ) | ( G2 ) | | | unloading, | spiral | spiral | con-| | assembly | casing | casing | trol| | | MIV | MIV | | +---------------+-----------+-----------+-----+ | draft tubes -> tailrace ``` ## Check yourself The answer's key points as multiple-choice questions, with the correct option and why. 1. What mainly sets the centre-to-centre spacing of units? A. Spiral casing width or generator barrel diameter plus clearance B. Tailrace slope C. Weir length D. Tunnel length Answer: A. The larger of casing or generator size plus clearances fixes spacing. (Key point: Unit spacing) 2. What is the erection (service) bay for? A. Drainage B. Housing the switchyard C. Unloading, assembly and maintenance of heavy equipment D. Storing water Answer: C. It is added to the length, about 1-1.5 unit spacing. (Key point: Erection bay) 3. Which fixes the powerhouse height? A. Turbine setting level (cavitation, tailwater), draft tube depth, and crane clearance B. River width C. The number of transmission lines D. Only the penstock diameter Answer: A. Setting level, draft tube substructure and crane lift height decide the height. (Key point: Height factors) 4. Why consider the flood level? A. To shorten the tailrace B. To avoid a crane C. The floor must be above maximum flood while the draft tube outlet stays submerged D. To lower the floor Answer: C. This protects the powerhouse and keeps the draft tube sealed. (Key point: Flood level) ## Related in Hydro Power - [Powerhouse layout with Francis turbine](https://www.bctengineer.com/question.md?key=semester_6%2Fhydro_power%3Apowerhouse-layout-francis) — Hydro Power, chapter 5 - [Firm power and plant load factors](https://www.bctengineer.com/question.md?key=semester_6%2Fhydro_power%3Afirm-power-load-factors) — Hydro Power, chapter 3 - [Intake site selection for RoR plant](https://www.bctengineer.com/question.md?key=semester_6%2Fhydro_power%3Aintake-site-selection-ror) — Hydro Power, chapter 5 - [Flow duration curve and planning parameters](https://www.bctengineer.com/question.md?key=semester_6%2Fhydro_power%3Afdc-planning-parameters) — Hydro Power, chapter 3 - [Power duration curve and primary/secondary energy](https://www.bctengineer.com/question.md?key=semester_6%2Fhydro_power%3Apower-duration-curve-energy) — Hydro Power, chapter 3 - [Criteria for designing and laying out tunnels](https://www.bctengineer.com/question.md?key=semester_6%2Fhydro_power%3Ahydraulic-tunnel-design-layout) — Hydro Power, chapter 5, asked 2× ## Related in other subjects - [Fixing approximate powerhouse dimensions](https://www.bctengineer.com/question.md?key=semester_7%2Fhydropower_engineering%3Apowerhouse-dimension-functional-requirements) — Hydropower Engineering, chapter 8, asked 2× - [Powerhouse general arrangement and dimensions](https://www.bctengineer.com/question.md?key=semester_7%2Fhydropower_engineering%3Apowerhouse-arrangement-and-dimensions) — Hydropower Engineering, chapter 8, asked 3× - [Powerhouse types; plan with three units](https://www.bctengineer.com/question.md?key=semester_7%2Fhydropower_engineering%3Apowerhouse-types-plan-three-units) — Hydropower Engineering, chapter 8 - [Powerhouse plan and sections (Francis, 10 MW)](https://www.bctengineer.com/question.md?key=semester_7%2Fhydropower_engineering%3Apowerhouse-plan-section-francis-10mw) — Hydropower Engineering, chapter 8