Otis Singleton
Electric power transmission is the bulk movement of electricity from a generating site, such as a power plant, to an electrical substation. This is done through transmission networks, which are made up of interconnected lines. Efficient long-distance transmission requires high voltages, which reduce energy loss due to resistance. This electricity is then distributed to consumers through local wiring between high-voltage substations and customers. While electricity can be dangerous, safety measures such as Class A Ground Fault Circuit Interrupters (GFCIs) are in place to prevent severe injuries or electrocution. Additionally, transmission companies determine the maximum reliable capacity of each line to ensure spare capacity in the event of a failure. These safety measures and careful planning help ensure that electricity can be transported safely without posing a danger to people or property.
| Characteristics | Values |
|---|---|
| Electricity travels at nearly the speed of light | 186,000 miles per second |
| High voltage | Over 600 volts |
| Low voltage | Between 10 and 30 volts |
| High current | Over 60 A |
| Low current | 2-3A |
| High frequency | Very high frequency |
| Human body composition | 70% water |
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What You'll Learn
- Electric vehicles (EVs) use on-board battery packs to power the motor, reducing reliance on gasoline
- Electricity transmission is safer at high voltages, minimising energy loss over long distances
- Underground power transmission is safer in urban areas, but has higher installation costs
- Safety measures like Class A Ground Fault Circuit Interrupters (GFCIs) prevent severe electrical injuries
- Most US households can charge EVs at home, minimising public charging infrastructure needs
Electric vehicles (EVs) use on-board battery packs to power the motor, reducing reliance on gasoline
Electric vehicles (EVs) are powered by electricity, which is a much cleaner energy source than gasoline. EVs use on-board battery packs to power their electric motors, reducing reliance on gasoline and improving fuel economy. This is in contrast to traditional cars, which use internal combustion engines that burn gasoline or diesel to generate power.
The concept of battery electric vehicles (BEVs) is to use charged batteries on board the vehicle for propulsion. BEVs use stored electrical energy in a battery pack to fully operate and move the vehicle. The battery pack powers the electric traction motor, which drives the vehicle's wheels. The motor controller determines how much electric power is needed and regulates the power to the motor. It also handles regenerative braking, where energy is recaptured as the vehicle slows down and is used to recharge the battery.
BEVs have no fuel tanks and must be plugged into a charging station or the electrical grid to replenish their energy storage. They are considered zero tailpipe emission vehicles because they do not emit any criteria pollutants or greenhouse gases while operating. Even when accounting for the emissions from generating the electricity used to charge BEVs, research shows that they are typically responsible for lower levels of greenhouse gases than an average new gasoline car.
While there are some concerns about the electromagnetic radiation emitted by electric vehicles, the automotive industry has ensured that this radiation is shielded by means of insulation and sheathing. Manufacturers design the components of electric vehicles to emit as little radiation as possible, and governments have set limits for electromagnetic fields to protect public health.
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Electricity transmission is safer at high voltages, minimising energy loss over long distances
Electric power transmission is the bulk movement of electricity from a generating site, such as a power plant, to an electrical substation. The transmission network is made up of interconnected lines that facilitate this movement. Efficient long-distance transmission of electric power requires high voltages.
Transmission of power at high voltages helps achieve lower power loss, lower voltage drops, improved system efficiency, and reduced overall cost of power transmission. This is because power loss in transmission lines is proportional to the current flowing through them. Therefore, by transmitting electricity at high voltages, the current is reduced, which in turn reduces heating losses. Joule's first law states that energy losses are proportional to the square of the current. Thus, reducing the current by a factor of two lowers the energy lost to conductor resistance by a factor of four for any given size of the conductor.
High-voltage direct current (HVDC) is used to transmit large amounts of power over long distances or for interconnections between asynchronous grids. When electrical energy is transmitted over very long distances, the power lost in AC transmission becomes appreciable, and it is less expensive to use direct current instead. HVDC technology is also used in submarine power cables, typically longer than 30 miles (50 km), and in the interchange of power between grids that are not synchronized.
Transmission lines are sized based on the maximum current they must carry. If power is transmitted at a lower voltage, the size of the conductor required is much higher than that for power transmission at higher voltages. Therefore, transmission of power at higher voltages enables a reduction in the conductor required, which facilitates the reduction of conductor cost.
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Underground power transmission is safer in urban areas, but has higher installation costs
The transportation of electricity is made safe by the use of insulated cables, which prevent electric shock. Aerial cables are spun between poles and insulated to remove the danger of electric shock, unless the cables are damaged. However, the insulation on underground cables can deteriorate over time, allowing moisture to enter and cause shorts.
Underground power transmission is safer in densely populated urban areas, as it reduces the risk of electric shock and damage from severe weather conditions, such as high winds, thunderstorms, heavy snow, and ice storms. Underground cables also pose no hazard to low-flying aircraft or wildlife. Additionally, they cannot be damaged by human activity, such as theft, illegal connections, or sabotage.
However, installing power lines underground has much higher installation costs. For example, a typical new 69 kV overhead single-circuit transmission line costs around $285,000 per mile, while a new 69 kV underground line costs $1.5 million per mile. The higher cost of underground installation is due to the need for insulated conductors, higher-cost conductors, and other insulating infrastructure. Underground installation also requires more labour and civil engineering work, as well as trenching, which can cost $5 to $12 per linear foot.
The higher costs of underground power transmission are a significant impediment to its more extensive use, despite its safety benefits in urban areas.
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Safety measures like Class A Ground Fault Circuit Interrupters (GFCIs) prevent severe electrical injuries
Electrical injuries can be extremely dangerous and even fatal. The dangers of electricity have been known since the 1880s, and yet, in the modern world, we are surrounded by it in our homes and workplaces. Therefore, safety measures are of paramount importance to prevent severe electrical injuries.
One such safety measure is the use of Class A Ground Fault Circuit Interrupters (GFCIs). GFCIs are electronic devices that can prevent electrical shocks and burns by shutting off electrical power when they detect ground faults. They are designed to disconnect a circuit when an unbalanced current is detected between an energised conductor and a neutral return conductor. This imbalance can be caused by current "leaking" through a person who is simultaneously in contact with a ground and an energised part of the circuit. GFCIs are installed by qualified electricians in areas where electrical devices can come into contact with water, such as kitchens, bathrooms, and garages, as well as outdoors near swimming pools or where power tools are used.
The rapid tripping mechanism of GFCIs after earth leakage detection is crucial to their life-saving function. When the amount of current going out differs from the amount returning by approximately 5 milliamperes, the GFCI interrupts the current. This rapid response prevents ventricular fibrillation, which is often the cause of death attributed to electric shock. GFCIs are designed to trip so quickly that even if a person receives a shock, it will not be harmful.
It is important to note that GFCIs should be tested regularly to ensure they are functioning properly. They can be damaged or wear out over time, and while the electrical receptacle may continue to function, the GFCI circuit may not. In such cases, it is recommended to have a qualified electrician replace the GFCI as soon as possible.
GFCIs are an essential safety measure to prevent severe electrical injuries, especially in areas where water and electricity can come into contact. They are designed to protect against the most common form of electrical shock hazard, the ground-fault, and their presence can provide peace of mind and enhanced safety in homes and workplaces.
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Most US households can charge EVs at home, minimising public charging infrastructure needs
The transition to electric vehicles (EVs) is well underway, and the US is making strides in EV adoption. Most US households can charge EVs at home, which minimises the need for extensive public charging infrastructure. As of 2023, the US had over 180,000 public chargers, with a goal of 500,000 by 2030. However, the majority of EV charging occurs at home, with 83% of US EV owners charging their vehicles at home. This high percentage of home charging reduces the strain on public infrastructure, allowing for a smoother transition to EVs.
While home charging is convenient for those with garages or driveways, it is not an option for everyone. Residents of multi-family buildings or those without dedicated parking may not be able to install home chargers. This limitation highlights the importance of public charging infrastructure to support EV adoption among these populations. Public charging stations offer flexibility, equitable access, and ease of use, addressing concerns about range anxiety for long-distance travellers.
To enable widespread EV adoption, a robust and equitable network of public charging stations is necessary. This includes ensuring interoperability between charging stations and vehicles, as well as diverse payment options, including credit cards, mobile apps, and subscription plans. Federal funding initiatives, such as the National Electric Vehicle Infrastructure Formula Program, are contributing to the expansion of public charging networks. Additionally, private companies are also stepping in to provide charging stations in parking areas of hotels, restaurants, and shopping centres, further bolstering the charging infrastructure.
The availability of direct-current (DC) fast charging is also increasing due to federal funding and the adoption of medium- and heavy-duty EVs. As of 2023, more than 20% of public EV charging ports in the US offered DC fast charging, enhancing the convenience and efficiency of EV charging.
Overall, while most US households can charge EVs at home, continued development of public charging infrastructure is necessary to support those who cannot charge at home and to encourage wider EV adoption. This includes increasing the number of charging stations, ensuring interoperability and diverse payment options, and expanding fast-charging capabilities.
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Frequently asked questions
Electricity is transmitted at high voltages to reduce energy loss due to resistance over long distances. This transmission system has safety and fault tolerance margins, and the voltage is stepped up for transmission and then reduced for local distribution.
Transmission refers to the bulk movement of electricity from a generating site to an electrical substation. Distribution refers to the local wiring between high-voltage substations and customers.
A Class A Ground Fault Circuit Interrupter (GFCI) detects any loss of electrical current and turns off the electricity to prevent severe injuries or electrocution. GFCI wall outlets can be installed to protect against electrocution for a specific outlet.
Do not use electrical equipment in wet conditions or clean tools with flammable or toxic solvents. Keep power cords clear of tools during use and ensure they are straight and not twisted. Do not enter an electrical power substation or marked areas.
Open the car door and prepare to jump, keeping your feet together and arms close to your body. Do not touch the vehicle and the ground at the same time. Shuffle at least 10 meters away before taking a normal step.
