--- title: "Civil, mechanical and electrical components" subject: "Power Plant Design" chapter: 3 key: "semester_8/power_plant_design:hydropower-civil-mech-elec" source: https://www.bctengineer.com/q/semester_8/power_plant_design/hydropower-civil-mech-elec site: BCT Engineering --- # Civil, mechanical and electrical components Power Plant Design · Chapter 3: Hydro Power Plant Design - Asked in: 2080 Chaitra, 8 marks - Video: [Hydro power plant, Parts of Hydro plant, Components of Hydro plant #HydroPlant #PowerPlant](https://www.youtube.com/watch?v=3ixtdPORwsw) — Mechanical Engineering Management - Answer checked by Claude Opus 5.5 (high effort) on 2026-10-14 - Page: https://www.bctengineer.com/q/semester_8/power_plant_design/hydropower-civil-mech-elec - Whole chapter: https://www.bctengineer.com/md/semester_8/power_plant_design/chapter-3 ## Question Draw schematic diagram of a hydropower plant and explain the basic civil, mechanical and electrical components used. ## Short answer Hydropower plant has civil components (dam, intake, desander, headrace, surge tank/forebay, powerhouse, tailrace), mechanical (penstock, valve, turbine, governor, draft tube), electrical (generator, excitation, transformer, switchyard). Water flows from reservoir through intake, tunnel, surge tank, penstock to turbine, then tailrace. ## Answer A hydropower plant converts the potential energy of water into electricity. Its works are grouped into **civil**, **mechanical** and **electrical** components. ```text River/Reservoir ==|== Dam/weir [CIVIL] | Intake, desander | Headrace tunnel/canal | Surge tank / forebay v Penstock -> Valve [MECH] v Turbine ---- Generator [MECH] [ELEC] | Governor | Excitation Draft tube v | GCB -> GSU transformer Tailrace v [ELEC] v Switchyard -> Transmission line River ``` #### Civil components - **Dam / diversion weir:** raises water level, creates head or storage; includes spillway and undersluice. - **Intake:** trash rack and gates admit design flow. - **Gravel trap and desander:** remove sediment. - **Headrace canal or tunnel:** conveys water with low head loss. - **Forebay or surge tank:** provides a free water surface, absorbs water hammer. - **Powerhouse:** building or cavern for units, crane and control room. - **Tailrace:** returns water to the river. - **Access roads, anchor blocks and saddles** for the penstock. #### Mechanical components - **Penstock:** steel pipe that delivers water under pressure. - **Main inlet valve:** butterfly or spherical valve. - **Turbine:** Pelton (high head), Francis (medium head), Kaplan (low head). - **Governor:** controls flow to keep speed and frequency constant. - **Draft tube:** recovers outlet energy of reaction turbines. - **Auxiliaries:** cooling water, lubrication and oil pressure units, compressed air, EOT crane, dewatering and drainage pumps, fire fighting. #### Electrical components - **Generator:** synchronous, usually 11 kV. - **Excitation system and AVR:** brushless or static; control voltage and reactive power. - **Generator circuit breaker and bus duct.** - **Generator step-up transformer:** e.g. 11/132 kV. - **Switchyard:** circuit breakers, isolators, CTs, PTs, lightning arresters, busbars. - **Auxiliary supply:** station transformer, DC battery and charger, diesel generator for black start. - **Protection, control, metering, SCADA and communication (PLCC/OPGW).** - **Earthing system:** grounding mat for powerhouse and switchyard. ## Check yourself The answer's key points as multiple-choice questions, with the correct option and why. 1. Which group do the penstock, turbine and governor belong to? A. Civil components B. Mechanical components C. Electrical components D. Protection components Answer: B. Penstock, main valve, turbine, governor and draft tube are mechanical; the dam and tunnel are civil. (Key point: Classification) 2. Which turbine type suits each head? A. Pelton low, Francis medium, Kaplan high B. Kaplan high, Pelton medium, Francis low C. Pelton high, Francis medium, Kaplan low D. All turbines suit all heads equally Answer: C. Head decides the type: impulse for high head, Francis for medium, Kaplan for low. (Key point: Turbine by head) 3. What does the governor do? A. Steps up generator voltage B. Removes sediment C. Controls generator reactive power D. Controls flow to keep speed and frequency constant Answer: D. The governor adjusts water flow to keep turbine speed, and hence frequency, constant. (Key point: Governor) 4. What is the function of the excitation system and AVR? A. Control generator voltage and reactive power B. Control turbine speed C. Protect against lightning D. Supply black-start power Answer: A. The AVR regulates the field current to control terminal voltage and reactive power. (Key point: Excitation and AVR) ## Related in Power Plant Design - [Reservoir type hydropower plant schematic](https://www.bctengineer.com/question.md?key=semester_8%2Fpower_plant_design%3Areservoir-plant-schematic) — Power Plant Design, chapter 3 - [Schematic of a PROR hydropower plant](https://www.bctengineer.com/question.md?key=semester_8%2Fpower_plant_design%3Apror-schematic-components) — 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× - [High dam hydropower project components](https://www.bctengineer.com/question.md?key=semester_8%2Fpower_plant_design%3Ahigh-dam-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× - [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× ## Related in other subjects - [Combined plant components and T-s diagram](https://www.bctengineer.com/question.md?key=semester_7%2Fpower_plant_equipment%3Acombined-components-ts) — Power Plant Equipment, chapter 8, asked 4× - [Electrical and mechanical requirements of insulators](https://www.bctengineer.com/question.md?key=semester_4%2Fpower_system_analysis_i%3Ainsulator-requirements) — Power System Analysis I, chapter 2 - [Hydropower generation with block diagram](https://www.bctengineer.com/question.md?key=semester_4%2Fpower_system_analysis_i%3Ahydropower-generation-block-diagram) — Power System Analysis I, chapter 1 - [Schematic diagram of rural gravity scheme](https://www.bctengineer.com/question.md?key=semester_5%2Fwater_supply_engineering%3Arural-gravity-scheme-diagram) — Water Supply Engineering, chapter 1, asked 5×