Electric Power Principles - Module 1 Continued

Classification of Power Plants

• Power plants are classified into conventional and non-conventional types.

Conventional Power Plants

• Steam/Thermal Power Plants: Use heat to generate electric energy.
• Diesel Power Plants
• Gas Turbine Power Plants
• Hydro-Electric Power Plants: Harness energy from water flow.
• Nuclear Power Plants

Non-conventional Power Plants

• Solar System
• Wind Energy Power System
• Geothermal Energy
• Ocean Thermal Energy Conversion (OTEC)
• Wave and Tidal Wave
• Thermoelectric Generator
• Thermo-ionic generator
• Biogas, Biomass Energy Power system

Major Power Plants (Thermal Power Plants)

• Steam power plant
• Diesel power plant
• Gas turbine power plant
• Nuclear power plant

Hydro Power Plant

• Utilizes the energy of water to move turbines, which in turn run electric generators.
• Takes advantage of water head and flow characteristics.
• Water energy can be kinetic or potential.
• Conventional renewable energy source; clean and pollution-free.
• Requires large investment and can increase power transmission costs.
• Long useful life (about 100-125 years).
• Low maintenance costs compared to thermal power plants.
• Can be started quickly.

Total Power Generated by Hydro Power Plant

$P = \, \eta \cdot g \cdot H \cdot Q$

• Where:
  • $g$ = acceleration due gravity = $9.81 m/s^2$
  • $H$ = Effective head of water in m
  • $Q$ = rate of flow of water in $m^3/s$
  • $\rho$ = Density of water = $1000 kg/m^3$
  • $\eta$ = Efficiency
• $1 ft = 0.3048 m$

Steam Power Plant (Thermal Power Plant)

• Heat energy is converted into electrical power using a steam turbine.
• Heated water is converted into steam, rotating the turbine which operates an electric generator.
• Fuel cost is relatively low.
• Heat production system is simple.
• Can be located almost everywhere, preferably in areas with minimal human traffic.

Steam Power Plant Stages

• Stage 1: Coal is burned in the boiler furnace to produce heat. Carbon in the coal combines with Oxygen in the air to produce Carbon Dioxide ($CO_2$) and heat.
• Stage 2: Thermodynamic process. Boilers produce steam at high pressure and temperature.
• Stage 3: Rotation of the turbine rotates the generator rotor to produce electricity based on Faraday’s Principle of electromagnetic induction.

Gas Turbine Power Station

Working Principle

• Air is drawn into the compressor, where it is compressed.
• Compressed air enters the combustion chamber, where fuel is burned.
• High-temperature, high-pressure gas drives the turbine.
• The turbine converts gas energy into mechanical energy, driving the generator to produce electricity.

Components

• Compressor: Typically of rotatory type. Air is drawn through a filter to remove dust, and rotatory blades push the air between stationary blades to raise its pressure.
• Regenerator: Recovers heat from the exhaust gases of the turbine. Compressed air passes through tubes in a shell, heated by the hot exhaust gases en route to the combustion chamber.
• Combustion Chamber: Air at high pressure from the compressor is led to the combustion chamber via the regenerator. Heat is added to the air by burning oil. Oil is injected through the burner into the chamber at high pressure to ensure atomization and thorough mixing with air, resulting in very high temperature. The combustion gases are then cooled and delivered to gas turbine.
• Gas Turbine: Products of combustion (mixture of gases at high temperature and pressure) are passed to the gas turbine. These gases pass over the turbine blades, expand, and thus do the mechanical work. The temperature of the exhaust gases from the turbine is about $900^oF$.
• Alternator: Coupled to the gas turbine. Converts the mechanical energy of the turbine into electrical energy.
• Starting Motor: An electric motor is mounted on the same shaft as the turbine to start the compressor. Energized by batteries. Once the unit starts, a part of the mechanical power of the turbine drives the compressor, and the motor is no longer needed.

Wind Power Plant

• A wind turbine is used as a prime mover to drive the rotor shaft of a generator.
• Wind turbines convert the kinetic energy to mechanical energy, which is then used to drive a generator that converts this energy into electricity.

Power extracted from wind plant:

$P = \frac{1}{8} \cdot \pi \cdot \rho \cdot D^2 \cdot C_p \cdot V^3$

• Where
  • $D$ = Rotor diameter
  • $C_p$ = Coefficient of performance
  • $V$ = wind speed (m/s)
  • $\rho$ = Air density

Wind Farms

• Wind farms typically have multiple turbines arranged in series.
• The electrical power produced depends on the amount of air power reaching the blades.
• Built on land and offshore to harness wind power.

Scales of Operation

• (a) Small: 0.5-10kW for isolated single premises
• (b) Medium: 10-100kW for communities
• (c) Large: 1.5 MW for connection to power supply systems (National Grid).

Solar energy to Plant

• Back-up supply to costumers necessary due to load demand fluctuation

• The main component is the ray collector.

• The energy received by the collector per square meter (Net) = $q$

$q = \text{some equation}$

$Q = \epsilon -(\text{some expressions})$

Maximizing Solar Panel Energy Output

• Regular Cleaning: Removes obstructions like dust and debris for optimal light absorption.
• Proper Panel Positioning: Ensures maximum sun exposure, adjusting for seasonal changes.
• Preventative Maintenance: Monthly inspections for visual checks, tightening, or listening for issues. Use a CMMS like 60Hertz Energy to quickly resolve issues.
• System Upgrades: Incorporates efficient technologies for enhanced performance.
• Critical Spares: Keep an inventory at the site or headquarters, of specific parts with a high frequency of replacement.

Power Substation

• A substation is a subsidiary station within the electricity generation, transmission, and distribution system.
• Serves as an intermediary between transmission lines and distribution lines.
• Includes transmission and distribution substations.
• Transforms voltage levels (high to low or vice versa) using transformers.

Example: A 115 kV to 41.6 kV 60 Hz substation

Important Considerations for Sub-Station Layout

• Located at a proper site, as far as possible, at the center of gravity of the load.
• Safe and reliable arrangement.
• Consideration of maintenance facilities for repairs and checking abnormal occurrences (explosion, fire, etc.).
• Easy operation and maintenance.
• Minimum capital cost.

Functions of Electrical Power Substations

• Continuous supply of electric power to consumers.
• Supply of electric power within specified voltage and frequency limits.
• Shortest possible fault duration.
• Optimum efficiency of plants and the network.
• Supply of electrical energy to the consumers at lowest cost

Components of Power Substations

• Besides the transformers, the several other equipment include:
  • Busbars
  • Circuit breakers
  • Isolators
  • Surge arresters
  • Substation Earthing System
  • Current transformers
  • Voltage transformers
  • Metering and Indicating Instruments.
  • Shunt reactors
  • Shunt Capacitors etc.

Busbars

• Conducting bars to which a number of circuits are connected.
• Copper or aluminum bars (generally rectangular x-section) that operate at constant voltage.
• The incoming and outgoing lines in a substation are connected to the bus bars.

Bus-bar Arrangements:

• Single bus-bar arrangement
• Single bus-bar system with sectionalisation
• Double bus-bar arrangement

• Consists of a single bus-bar, and all the incoming and outgoing lines are connected to it.

• Low initial cost
• Less maintenance
• Simple operation

• The single bus bar is divided into sections, and the load is equally distributed in all the sections.
• Any two sections of the bus-bar are connected by a circuit breaker and isolators.

• Isolation of a faulty section without affecting the supply from other sections.
• Repairs and maintenance of any section by de-energizing that section only.
• Used for voltages up to 33 kV.

• Consists of two bus-bars, a “main” bus-bar and a “spare” bus-bar.
• Each bus-bar has the capacity to take up the entire sub-station load.
• The incoming and outgoing lines can be connected to either bus-bar with a bus-bar coupler (circuit breaker and isolators).
• Ordinarily, the incoming and outgoing lines remain connected to the main bus-bar.

Insulators

• Support the conductors (or bus- bars) and confine the current to the conductors.
• Commonly made of porcelain.

Types:

• Pin type
• Suspension type
• Post insulator
• Etc.

Isolating Switches

• Disconnect a part of the system for general maintenance and repairs.
• Designed to open a circuit under no load.
• Operated only when the lines carry no current.

Circuit Breaker

• Equipment that can open or close a circuit under normal as well as fault conditions.
• Operated manually (or by remote control) under normal conditions and automatically under fault conditions via a relay circuit.
• Bulk oil circuit breakers (BOCB) are used for voltages up to 66kV, while low oil circuit breakers are used for high (>66 kV) voltages.

Instrument Transformers

• Used because the lines in sub-stations operate at high voltages and carry high currents.
• Measuring instruments and protective devices are designed for low voltages (generally 110 V) and currents (about 5 A).

Function

• Transfer voltages or currents in the power lines to values convenient for the operation of measuring instruments and relays.

Types

• Current transformer (C.T.)
• Potential/Voltage transformer (P.T.)

Metering and Indicating Instruments

• Meters (e.g., ammeters, voltmeters, energy meters, etc.) are installed in a sub-station to monitor circuit quantities.
• Instrument transformers are used with the meters for satisfactory operation.