Just by flipping a switch, appliances function, the lights come on, and factories can function. Ever wondered how this is accomplished? The process of delivering electricity to our homes and workplaces involves several steps. In today’s guide, we will provide our readers with a detailed introduction to what a power transmission system is and its advantages.
1. What is the power transmission system
The transfer of energy from its source to a point where it can be used to carry out productive tasks is known as power transmission. Power transmission is typically synonymous with electric power transmission due to the widespread installation of electrical grids.
To reduce resistive loss in the conductors used to transmit power over long distances, alternating current is typically preferred because its voltage can be easily stepped up by a transformer. At the destination, a second set of transformers is needed to step the voltage back down to safer or more usable levels.
Overhead lines are typically used for power transmission since it’s the most cost-effective method. High-voltage direct-current (HVDC) submarine connections and densely populated urban regions are two scenarios where underground transmission using high-voltage cables is preferred.
Radio waves or shifting electromagnetic fields can also be used to transport power. Wireless power transfer allows microwave energy to be efficiently transferred over open spaces or short distances using a waveguide.
major characteristic
Through a network of transmission lines, substations, and transformers, an AC transmission system transfers electrical power from generation stations to end customers using alternating current (AC). The periodic reversal of the current direction, usually at a frequency of 50 or 60 Hz, depending on the location, is a major characteristic of alternating current.
Because it can easily convert voltage and is compatible with existing infrastructure, the AC transmission system is the most widely used means of power transmission.
2. Working principle of electrical power transmission system
Following production at generating stations, electrical energy is transmitted and distributed to customers for use. This is because generating stations are typically located far from the load centers. The transmission system is the network that moves power from the generating stations to consumers. Both AC and DC energy can be used to transfer this energy. Although AC has been the norm for many years, HVDC, or high voltage DC, is becoming more and more common.
Commonly, or typically, generating stations in Europe and some other countries produce electricity at 11 kV. However, the generating voltage may occasionally be higher or lower. Several large manufacturers offer generating machines with voltages ranging from 6 kV to 25 kV for use in power plants. The voltage that is being generated is then increased to higher voltages. Increasing the voltage level is contingent upon the transmission distance. The voltage level is increased for longer distances.
Raising the voltage has the effect of lowering the I2R losses in power transmission since it causes a relative decrease in current, which keeps the power constant and lowers I2R loss as well. We refer to this phase as the primary transmission.
At a receiving station, the voltage is stepped down to 33 kV or 66 kV. This receiving station gives rise to secondary transmission lines that link substations close to load centers.
At a substation, the voltage is stepped down one more time to 11 kV. These substations may directly supply 11 kV to large industrial users. Additionally, feeders take power from these substations. We refer to this phase as primary distribution.
Feeders are subterranean or overhead wires that transmit power up to a few kilometers near the load terminals, or end users. Ultimately, a distribution transformer installed on a pole reduces the power to 415 volts before it is sent to the distributors. Distributors supply end users through a service main line. Feeders, distributors, and service mains make up the secondary distribution system.
3. Principal components or elements in power transmission systems
Three-phase three-wire overhead systems are commonly employed for the transmission of electric power due to economic factors. The principal components of a standard power system are listed below.
Conductors: A single circuit line requires three conductors, while a double circuit line requires six. The current capacity and right size of conductors are required (i.e. cross-sectional area) to do its job effectively. ACSR (Aluminum-core, Steel-reinforced) conductors are commonly used.
Generation Stations: These are the locations where power is produced. This could be nuclear, hydraulic, thermal, or any other type.
Transmission lines: Transmission lines are how electricity is transferred from the generating station to the substation.
Protective devices: Protective devices are used to guarantee dependable operation and safeguard the transmission system. These consist of relays, circuit breakers, lightning arrestors, ground wires, etc.
Substations: Voltage is dropped at the substations from, for example, 220 kV to 33 kV, then to 11 kV, and so forth so it can be distributed locally.
Line Insulators: The purpose of line insulators is to electrically isolate the line conductors from the support towers while providing mechanical support for them.
Load centers: Load centers are where industrial and residential customers are connected to the grid.
Support towers: These are used to hold up the overhead line conductors that are suspended in the air.
Voltage regulators: They are used to maintain the voltage at the receiving end within allowable limits.
Transformers: The voltage level can be stepped up or down using step-up or step-down transformers, respectively. Transformers provide a more efficient transmission of power.
4. Different types of transmission systems
The following are the different types of transmission systems.
1. Single-phase AC system
• three wires, single phase
• single phase, two wires with a midpoint earthed
• two wires, single phase
2. Two-phase AC system
• four wires, two-phase
• two-phase, three wires
3. Three-phase AC system
• three-phase, four wires
• three-phase, three wires
4. DC system
• DC three wires
• DC two wires with midpoint earthed
• DC two wires
5. Advantages of AC transmission systems
1. Ease of Voltage Transformation: AC voltage levels can be readily increased or decreased with transformers, facilitating effective long-distance transmission and safe voltage distribution to consumers.
2. Control and Protection Mechanisms: The sophisticated control and protection mechanisms that exist in AC systems contribute to the stability and dependability of the system.
3. Cost-Effectiveness: Because AC transmission requires less initial setup cost and already has infrastructure in place, it is typically more economical than DC transmission for short to medium distances.
4. Easy Connection to Loads and Generators: Since generators and loads are usually made to run on AC power, connecting and disconnecting them from the grid becomes a simple process.
5. Infrastructure: Because AC transmission systems have a well-established infrastructure, it is easier to combine them with new technologies and they are compatible with current power grids.
Disadvantages of AC Transmission System
6. Complexity in Long-Distance Transmission: To control reactive power and sustain voltage levels over long distances, AC transmission calls for more sophisticated infrastructure and equipment.
7. Higher Transmission Losses: The effects of capacitance, inductance, and resistance in the transmission lines, particularly over long distances, cause higher transmission losses in an AC transmission system.
8. Skin Effect: The tendency of AC current to flow close to conductor surfaces at high frequencies also referred to as the skin effect, increases energy losses and resistance.
9. Reactive Power Management: To ensure voltage stability during AC transmission, reactive power must be carefully managed, which can raise the system’s complexity and cost.
10. Electromagnetic Interference (EMI): Sensitive electronic devices and adjacent communication lines may be impacted by the electromagnetic interference produced by AC transmission networks.
6. Maintenance of power transmission systems
To guarantee continuous conformity with the regulations and codes, power transmission systems have to be maintained regularly. By doing so, system and equipment failures can be avoided, ensuring optimal safety and efficiency when using the facilities.
1) The Importance of Maintenance
Beyond simple routine maintenance, transmission line maintenance is critical to ensuring the overall power system’s security, dependability, and efficacy.
Without regular maintenance, transmission lines will be susceptible to several issues, including mechanical wear, corrosion, and environmental deterioration. These problems could cause power outages, jeopardize public safety, and incur high costs if they are not resolved.
2) Types of Maintenance
Maintenance of power transmission systems is the term for a variety of tasks intended to prolong the life of infrastructure, maximize performance, and prevent failures. These can be roughly divided into two categories:
1. Scheduled Maintenance
Regular inspections, repairs, and enhancements are performed as part of scheduled maintenance at predetermined intervals. One of the tasks includes vegetation control, or pruning trees and other vegetation along transmission lines to lessen the likelihood of outages caused by encroaching vegetation or falling branches.
As part of scheduled maintenance, it could also be necessary to replace aging parts like insulators and conductors to guarantee system reliability.
2. Predictive Maintenance
Diagnostic tools and advanced monitoring techniques are used in predictive maintenance to find potential issues before they become failures. Maintenance personnel can identify early indicators of potential equipment breakdowns by being proactive in identifying anomalous temperature fluctuations or vibration patterns. By using predictive maintenance solutions, operators can schedule maintenance procedures ahead of time to save operating costs and decrease downtime.
7. Power systems troubleshooting
The problems with power transmission systems and their solutions are as follows:
1. Transmission losses
The transmission of electricity over long distances raises the temperature inside power cables, which results in large energy losses. Regular electricity users are ultimately responsible for covering these losses.
Solution: Decentralization of energy will help solve this problem. A system of small local energy sources should replace a few large power plants to ensure that energy is used as close to its source as feasible, even at the level of individual residential structures.
2. Frequent blackouts
Blackouts are mostly caused by two factors: aging electricity cables and extreme weather conditions. Though they don’t happen very often in Europe, significant power outages have previously put millions of people in danger and cost billions of dollars in damages in some countries. Massive blackouts have the potential to destroy electronic equipment and erase crucial data in addition to impeding life in the impacted areas.
Solution: Greater independence in terms of energy. In the event of a power loss, backup sources like batteries can provide enduring protection and guarantee the ongoing operation of vital equipment. A distribution point can store green energy for later use by combining it with a renewable energy source.
8. Power transmission system FAQs
1. What is a power transmission system?
A power transmission system refers to the infrastructure needed for the bulk transportation of electric power from to source to places where it is needed. It serves as a vital link between the higher-voltage side of power generation and the lower-voltage side of energy transmission and distribution to end users.
2. What voltage is commonly applied to power transmission lines?
Common voltages for bulk power transmission over long distances by overhead lines fall between 110 kV and 765 kV in the majority of countries.
3. Why are transmission towers tall and spaced out?
For heavy conductors to clear obstructions with the proper ground clearances according to safety regulations, transmission towers must be high enough. Greater distances between phase conductors—0.5–1 km—reduce the need for steel and the effects of induction.
4. Which types of electric current are employed in transmission?
They include single-phase, two-phase, three-phase, and three-phase four-wire. Still, the advantages of smaller conductor sizes, balanced currents, and direct powering of big induction motors make three-phase the most popular.
5. Why does a power transmission system have multiple circuits?
The reason is that multiple circuits boost reliability, and transmission capacity and help to avert widespread blackouts by offering backup power flow channels if one or more circuits experience an outage due to maintenance or other issues.
9. Conclusion
Power transmission systems are built to transfer electrical energy from a source to a place where it can be used to do productive tasks. Energy transmission line maintenance and operation have a major impact on the efficacy, security, and dependability of power transmission networks.
By embracing sustainable practices, deploying cutting-edge technologies, and implementing proactive maintenance methods, utilities may minimize downtime, fix problems, and meet the evolving needs of modern civilization. Since energy is still essential to our daily lives, funding for transmission infrastructure maintenance is a necessary vehicle for a sustainable future.
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