How Is Electrical Energy Generated Transmitted?
Electrical energy is energy derived from electric charges and their movement. It is a fundamental part of modern society, providing power for lighting, electronics, appliances, motors, and more. There are several key steps involved in getting electrical energy from raw resources to end users.
First, energy sources like coal, nuclear fission, or renewable resources are used to generate electricity at power plants. This involves converting forms of energy like chemical, mechanical, or solar into electrical energy.
Next, the electricity must be transmitted long distances to homes, businesses, and other facilities. This is done by stepping up voltage for efficient transmission along power lines, then stepping down voltage for safe distribution and end use.
In this article, we will provide an overview of how electrical energy is generated at various types of power plants, then how it travels through transformers and transmission lines to ultimately power our modern world.
Generating Electrical Energy
Electricity is generated through various methods at power plants. The main methods for generating electricity are:
Fossil Fuel Power Plants
Fossil fuel power plants use coal, oil, or natural gas to produce electricity. In these plants, the fossil fuels are burned to heat water and produce steam. The steam then spins a turbine that is connected to a generator, which produces electricity.
Nuclear Power Plants
Nuclear power plants use the heat from nuclear fission reactions to produce steam. This steam then spins a turbine and generator to generate electricity. Nuclear power provides a major source of energy around the world.
Renewable Power Plants
Renewable energy comes from naturally replenishing sources. Types of renewable energy used to generate electricity include:
- Hydroelectric – Using flowing water from dams or tidal forces to spin turbines
- Wind – Using wind turbines to harness kinetic energy from the wind
- Solar – Converting energy from the sun into electricity using photovoltaic cells
Renewable energy is increasingly being used to generate electricity with minimal environmental impact.
Fossil Fuel Power Plants
Fossil fuel power plants generate electricity through the combustion of coal, natural gas, or oil. In a coal power plant, pulverized coal is ignited in a boiler to heat water into high-pressure steam. This steam then spins a turbine connected to an electrical generator to produce electricity. Coal plants require extensive pollution control measures to limit emissions of sulfur dioxide, nitrogen oxides, particulates, and mercury.
Natural gas power plants burn natural gas in a combustion turbine to spin a generator to create electricity. The heat from the turbine exhaust can be captured to create steam and spin a steam turbine for extra electricity generation. Natural gas plants emit 50-60% less carbon dioxide compared to coal plants.
Petroleum power plants are less common but use the combustion of oil to produce steam for spinning turbines. While more expensive than coal and natural gas, petroleum can be stored on-site providing backup generation when needed.
Fossil fuel plants provide reliable electricity and historically have been less expensive to operate than other options. However, fossil fuels are nonrenewable resources that emit air pollutants and greenhouse gases.
Nuclear Power Plants
Nuclear power plants produce electricity from the heat generated by splitting uranium atoms through a process called nuclear fission. Uranium rods placed in a nuclear reactor core undergo a chain reaction, releasing enormous amounts of energy in the form of heat. The reactor core contains moderators and control rods that regulate the fission reaction. Heat from the reactor core is used to boil water into steam. The high-pressure steam spins a turbine that drives a generator to produce electricity. After passing through the turbine, the steam cools and condenses back into water that is returned to the reactor core, creating a closed-loop system.
Nuclear power plants provide consistent, reliable baseload power without any greenhouse gas emissions. However, they do come with risks such as radioactive waste and potential nuclear meltdown accidents. Strict regulations and safety systems are in place to minimize these risks. Overall, nuclear power remains an important source of zero-emission electricity generation globally.
Renewable Power Plants
Renewable power plants generate electricity from inexhaustible sources like wind, water, sunlight, geothermal heat, and biomass. Some of the most common types of renewable power plants are:
Hydroelectric Plants
Hydroelectric plants use the energy of flowing water to spin large turbines connected to generators. Dams are built to create reservoirs that control water flow. As water is released from the reservoir, it flows through tunnels and channels into the turbines. Hydroelectric plants account for over 6% of total U.S. electricity generation.
Wind Plants
Wind plants use large wind turbines with blades that spin in the wind like giant propellers. The kinetic energy of the spinning blades turns a rotor connected to a generator to produce electricity. Wind power accounts for over 7% of total U.S. electricity generation.
Solar Plants
Solar plants use photovoltaic cells that directly convert sunlight into electricity through a semiconductor material. Arrays of PV cells are mounted in solar panels. Utility-scale solar plants have thousands of solar panels. Solar energy accounts for nearly 2% of total U.S. electricity generation.
Geothermal Plants
Geothermal plants extract hot water or steam from reservoirs under the earth’s surface to power turbine generators. The United States has an abundance of geothermal activity, especially in western states. Geothermal energy accounts for 0.4% of total U.S. electricity generation.
Biomass Plants
Biomass plants burn organic matter like wood, agricultural waste, and trash to produce steam for turning turbines. Biomass power accounts for 1.4% of total U.S. electricity generation. While biomass is renewable, its use as an energy source can still produce carbon emissions.
Transmitting Electrical Energy
Once electricity is generated at power plants, it must be transmitted long distances to reach homes and businesses. Transmitting electricity over long distances is made possible by the power grid – an interconnected network of transmission lines, substations, transformers and more that allows bulk transfer of electrical power from generating power plants to substations closer to end users.
The transmission system works by stepping up the generator voltage to very high levels with transformers, which allows more efficient transmission over long distances. The transmission lines efficiently carry electricity over hundreds of miles. Then, transformers at substations near end users step the voltage back down to safer levels for distribution.
Transmission lines are typically high voltage (115 kV to 765 kV) and made of aluminum conductor steel reinforced (ACSR) cable. The lines are suspended on tall transmission towers made of steel lattices or concrete poles. The grid is designed with redundancy so power can be rerouted if lines fail.
High voltage direct current (HVDC) transmission is also used for very long distances or subsea cables. HVDC converts AC to DC for efficient long-haul transmission, then back to AC for distribution. HVDC helps interconnect grids across regions.
Monitoring systems help grid operators manage the complex transmission system. Weather and other factors are monitored to prevent failures. The transmission system is crucial for providing electricity nationwide.
Step-up Transformers
Step-up transformers are a critical component of the electrical grid, allowing generated electricity to be transmitted efficiently over long distances. They work by transforming low-voltage electricity produced at power plants to high-voltage for transmission along grids.
Transformers consist of two separate coil windings around an iron core. The primary winding receives the low-voltage input from the generator while the secondary winding outputs higher voltage electricity. Based on principles of electromagnetic induction, when alternating current flows through the primary coil it creates a magnetic field in the core, inducing a higher voltage in the secondary winding due to it having more coils.
The voltage transformation follows this ratio: the output voltage is equal to the input voltage multiplied by the turns ratio of the windings. For example, if the input voltage is 10,000 volts and the secondary has four times as many turns as the primary, the transformer will step up the voltage to 40,000 volts. This allows the output electricity to travel long distances with minimal power losses.
Step-up transformers are essential for transmission as higher voltages more efficiently transport electricity over the grid. The high-voltage electricity can then be stepped down at substations nearer consumption points before distribution to end users. This vital transmission process powers the electricity needs of modern society.
Transmission Lines
Transmission lines are critical components of the transmission grid that carry electricity at high voltages over long distances. Electricity produced at power plants travels on these lines to electrical substations that evenly distribute it to local utility companies and end consumers.
The most common type of transmission line is the overhead power line, consisting of aluminum conductor cables strung between large steel towers or structures with heights of 60-170 feet or more. Thicker cables and higher voltages are used for main high-capacity transmission routes, while thinner lines are used for lower-capacity local connections. For extra-high voltage (500+ kV), bundled conductors can be used. Underground cables may also be used for a portion of urban power transmission.
Within the transmission grid, electricity flows in an interconnected network from power plants to substations in major load centers like cities and industrial areas. The interconnected nature provides redundancy so if one line fails, power can be rerouted. The transmission system in North America is divided into regional interconnections linked by DC ties, with three main grids – Eastern, Western, and Texas. Coordinated operators manage the flow of alternating current within each grid.
The transmission grid enables centralized power generation at plants with economies of scale and access to fuels like coal or natural gas. Transmitting high voltages over long distances leads to lower electrical losses compared to distributed low voltage networks. Managing the transmission grid is therefore crucial for delivering electricity efficiently across regions.
Step-down Transformers
After electricity has traveled long distances along high-voltage transmission lines, the voltage must be lowered or “stepped down” for safe distribution to homes and businesses. This is done through step-down transformers.
Step-down transformers are used to reduce the high voltage from transmission lines (typically 115 – 765 kV) to lower distribution voltages (less than 35 kV). The transformers work through electromagnetic induction between two windings – the primary winding connects to the higher incoming voltage while the secondary winding outputs the lower voltage.
The step-down transformer has wire coils around an iron core. The primary coil has fewer turns of wire than the secondary coil. When the primary coil receives the high voltage electricity, it creates a magnetic field in the core. This magnetic field induces a lower voltage in the secondary coil due to the turn ratio. For example, if the primary coil has 100 turns and the secondary coil has 10 turns, the secondary voltage will be stepped down to one tenth of the primary input voltage.
Step-down transformers are critical for the safe delivery of electricity. If the high transmission voltages were sent directly to homes and businesses, it could cause fires, electrocution hazards, and damage equipment. The transformers reduce voltage to safer levels for everyday use, while also maintaining
the efficiency of transmitting electricity at high voltages.
Distribution Systems
Distribution systems are responsible for delivering electricity from transmission systems to end users like homes, businesses, and factories. Distribution systems consist of lower voltage power lines, transformers, switches, and other electrical equipment.
After electricity has been stepped down in voltage by substations, it enters the distribution system. Distribution lines carry electricity with voltages ranging from 4kV to 35kV, compared to the higher voltages of 69kV to 765kV used in transmission lines. The lower voltages allow for the economical distribution of electricity in neighborhoods and communities.
Distribution systems include both primary and secondary lines. Primary distribution lines carry power from substations to distribution transformers located near businesses, homes, and buildings. Distribution transformers further reduce the voltage to levels typically less than 600V. From the distribution transformers, secondary distribution lines finally deliver the electricity into end users’ electrical systems.
The distribution system uses many protection and control devices to ensure reliable delivery of electricity. Equipment like voltage regulators, capacitor banks, reclosers, sectionalizers, and fuses all help control voltage levels and respond to system disturbances. Smart meters and other monitoring devices allow grid operators to observe the distribution system in real-time.
Efficient and robust distribution systems are vital in providing consumers and businesses with the electricity they need. As electricity demand grows and new technologies emerge, distribution systems must evolve using innovations like microgrids and distributed energy resources.
