Comprehensive Study Notes on Hydroelectric Power Engineering

Introduction to Hydroelectric Power Systems

Fundamental Physics and Energy Concepts:
- Water represents the most economical source of power for human civilization.
- Kinetic Energy: Kinetic energy of water is its energy in motion, calculated as a function of water mass and velocity.
- Potential Energy: Potential energy is a function of the elevation difference between two water points, designated as the hydraulic head.
- Continuity Requirement: Hydroelectric generation requires a continuous, reliable availability of water. Water is collected in high-altitude natural lakes or artificially stored reservoirs created by constructing dams across flowing streams and rivers.
- Economic Viability: Economical power generation requires an ample quantity of water maintained at a sufficient potential head.
Global Power Generation Statistics:
- Hydroelectric power supplies approximately $30\%$ of the total power in the world.
Historical Development of Hydroelectric Power in India:
- $1897$ : Implementation of a run-off river hydroelectric scheme near Darjeeling.
- $1902$ : Commissioning of India's first major hydroelectric power plant—the Sivasamudram scheme in Mysore—with a capacity of $4.5\,\text{MW}$ .
- $1914$ : Commissioning of the Khopoli hydro power project in Maharashtra with a capacity of $50\,\text{MW}$ .
- Pre-Independence Era: Total cumulative hydel power generation capacity across India was approximately $500\,\text{MW}$ only.
- Post-Independence Regional Milestones:
- Major hydel power stations at Srisailam and Nagarjuna Sagar were commissioned in $1982$ and $1983$ , respectively.

Major Hydroelectric Power Stations in South India

Prominent Regional Power Plants:
- Nagarjuna Sagar
- Nagarjuna Sagar tail
- Idukki
- Mettur Dam
- Linganamakki Dam
- Kadamparai pumped storage
- Jurala Project
- Lower Jurala Hydro Electric Project
- Pulichinthala Project
- Upper Sileru
- Lower Sileru
- Donkarayi
- Cheyali
Capacity Breakdown and Plant Configurations:
- Pulichinthala Project: $4 \times 30\,\text{MW} = 120\,\text{MW}$
- Upper Sileru: $4 \times 60\,\text{MW} = 240\,\text{MW}$
- Lower Sileru: $4 \times 115\,\text{MW} = 460\,\text{MW}$
- Donkarayi: $1 \times 25\,\text{MW} = 25\,\text{MW}$
- System Capacity Metrics: Total recorded power capacity metrics in the regional distribution include $6,419\,\text{MW}$ , $1,670\,\text{MW}$ , $1,608.2\,\text{MW}$ , and $1,240\,\text{MW}$ .

Requirements and Core Components of Hydroelectric Plants

Ten Core Structural Requirements:
1. Catchment area
2. Reservoir
3. Dam
4. Forebay
5. Waterways
6. Draft tube
7. Surge tank
8. Spillway
9. Trash tracks
10. Power house and equipment
Detailed Component Functions:
- 1. Catchment Area:
- The designated geographic area behind the dam that collects rainwater and drains it directly into a river or stream.
- 2. Reservoir:
- The storage basin behind the dam used for impounding water.
- Natural Reservoir: A natural lake situated high in mountain ranges.
- Artificial Reservoir: Created by building a dam across a river.
- 3. Dam:
- A solid masonry structure or other engineered material constructed at a suitable location across a river.
- Primary Functions:
  - Provides and raises the hydraulic head of water.
  - Creates artificial storage or pondage.
- 4. Forebay:
- An enlarged storage basin at the intake end of power canals where water is distributed into penstocks leading to turbines.
- Regulating Function: Serves as a regulating reservoir. It temporarily stores excess water when electrical load decreases and supplies additional water when electrical load increases.
- 5. Waterways:
- Channels, power canals, or pressure tunnels constructed to carry water from the reservoir or dam to the power house.
- 6. Draft Tube:
- A metallic pipe or concrete tunnel connecting the runner exit of the hydraulic turbine to the tailrace.
- Features a gradually increasing cross-sectional area towards the outlet at the tailrace to reduce discharge velocity and recover kinetic energy.
- 7. Surge Tank:
- A small intermediate reservoir or open vertical cylinder connected along the penstock conduit preceding the power house.
- Water Hammer Relief: Relieves severe pressure surges inside the penstock caused by sudden changes in water velocity.
- Load Balance Regulation: Holds excess water during turbine load rejection and rapidly supplies supplementary water during sudden load increases.
- 8. Spillways:
- Engineered discharge channels designed to safely release surplus floodwater from the storage reservoir to the downstream side of the dam.
- Serves as an essential safety valve to protect the structural integrity of the dam against overtopping.
- 9. Trash Tracks:
- Heavy intake screens installed to block floating debris, vegetation, and solids from entering penstocks and water turbines.
- 10. Power House and Internal Equipment:
- The central facility where hydraulic energy is converted into electrical energy.
- Primary Equipment Installed:
  - Water turbines
  - Electric generators
  - Governors
  - Relief valves for penstock filling
  - Main gate valves
  - Flow measurement equipment
  - Air ducts
  - Water circulating cooling pumps
  - Electrical reactors
  - Dedicated battery rooms
  - Low tension (LT) and high tension (HT) bus bars
  - Oil circuit breakers
  - Overhead cranes
  - Maintenance shops and administrative offices

Working Principle of Hydroelectric Power Stations

Hydraulic and Mechanical Flow Sequence:
- An artificial storage reservoir is formed by constructing a dam across a river or lake.
- A heavy pressure tunnel extracts water from the reservoir and directs it toward the valve house located at the head of the penstocks.
- A surge tank positioned immediately before the valve house stabilizes internal dynamic water pressure fluctuations.
Valve House Functions:
- Main Sluice Valves: Regulate the continuous volume of water routed into the power station.
- Automatic Isolating Valves: Automatically shut off the primary water supply in the event of a penstock rupture or burst.
Penstock and Energy Conversion System:
- Water flows from the valve house to hydro turbines through large-diameter steel or reinforced concrete pressure pipes called penstocks.
- Hydraulic to Mechanical Energy: Water entering the hydraulic turbine exerts force on turbine blades, converting hydraulic energy into rotational mechanical energy.
- Mechanical to Electrical Energy: An electrical alternator coupled directly to the turbine shaft converts rotational mechanical energy into usable electrical power.
- Tailrace Discharge: After performing work on the turbine blades, water is discharged into the downstream river channel through the draft tube to the tailrace.

Site Selection Criteria for Hydroelectric Power Plants

Essential Geological, Geographical, and Meteorological Factors:
- 1. Quantity of Water Available:
- Calculated based on multi-year rainfall records collected at multiple monitoring locations across the catchment area.
- Net available volume is determined by deducting estimated losses from surface evaporation and ground percolation.
- This calculation establishes the overall generation capacity of the hydroelectric power plant.
- 2. Storage of Water:
- Required because precipitation varies annually and seasonally, causing irregular natural river discharge.
- Water storage capacity necessary to ensure uniform flow is calculated using mass curves or by determining the minimum water quantity required for available storage volume.
- 3. Availability of Head of Water:
- Estimated using regional geological structures, topography, and hydrological stream flow data.
- A higher usable elevation drop increases generated electrical power per unit volume of water.
- 4. Distance from Load Centres:
- Hydroelectric power plants are typically constructed in remote, mountainous areas far from industrial and urban load centers.
- Site evaluation requires balancing local geographical dam advantages against long-distance transmission line costs and line loss economics.