Globally 160,000 TWh of energy is consumed every day through primary sources! That’s too much electricity and yet not enough.
As people become wealthier and populations rise, there is an increase in the need for energy in many nations around the world. In the absence of any increases in energy efficiency, this increased demand will result in an annual increase in our global energy consumption.
Electric power lines are used to carry the electrical energy that is generated at the generating stations to the locations of use. For the purpose of delivering electric power from the power plant to the consumer's location for use, the electric utility companies establish two different types of electric power lines, namely transmission lines and distribution lines.
What is a Transmission & Distribution Line?
Transmission lines are the electric power lines that transport high-voltage electricity from producing units to various substations. Typically, transmission lines transport power over great distances, like all the way across a state. More than 69 kV is the typical transmission voltage.
The transmission lines typically use three-phase, three-wire AC power transmission and are supported by massive steel towers. The transmission lines are divided into two sections: a primary transmission line that carries electricity from a power plant to a receiving station, and a secondary transmission line that carries electricity from the receiving station to substations.
Moreover, raising the transmitted voltage reduces the amount of power lost in transit from the utility generator to the destination. Up to 75% less power loss can be achieved by doubling the transmission voltage. The size and weight of the conductors necessary for high-voltage power transmission are reduced, allowing for smaller and closer-spaced poles and towers to support the wires. Consequently, smaller conductor sizes, higher power transmission, and cheaper construction and material costs are all made possible by higher transmitted voltages.
High-voltage distribution lines that provide three-phase power are grouped together on utility generators. A neutral/ground conductor is also run along with the power lines in addition to them. In order to help disperse lightning strikes, the neutral/ground conductor—which is utilized as a grounding wire—is installed above electrical lines. At every electricity pole, as well as at the transmission and distribution substations, the neutral/ground conductor is grounded. Before it reaches the end user, the voltage on the power wires is increased and decreased numerous times.
Understanding Distribution Lines
A distribution substation is essentially an outdoor structure that is situated close to the point where electrical service is used. It is used to redistribute electricity, alter voltage levels, and offer a central location for system monitoring, switching, and protection.
High transmission voltages are lowered for further distribution at distribution substations. Substations for transmission run at greater voltages than those for distribution, which run at lower voltages. Distribution substation output voltages typically vary from 12 kV to 13.8 kV.
During distribution system issues like power outages brought on by lightning strikes, distribution substations offer a place along the distribution system close to the end user where it is simple to test the system, modify voltage output, add new lines, disconnect lines, and reroute electricity.
Distribution lines are the power lines that transport electricity from substations to consumers. Typically, distribution lines transport electricity over small distances, like those found within cities. In most cases, timber poles, RCC poles, steel poles, etc. sustain the distribution lines.
The distribution lines in use might either be single-phase or three-phase. The 3-phase, 4-wire AC system used for distribution is a system with three wires for line conductors and one wire for neutral. Electricity is transported over distribution lines at a lower voltage.
Primary distribution lines transport power from the substation to the distribution station, and secondary distribution lines transport power from the distribution station to the final users.
Importance of Transformer in Transmission & Distribution Line
Many people have or will at some point in their life experience a transformer blowing. This typically means that until the problem is fixed, your house or place of business will be without electricity. Why do transformers "blows" and what exactly is a transformer?
Transformers are essential to the transmission and distribution process because they increase or decrease the voltage of an electrical supply. As we discussed above, during the transmission process, electricity is carried via overhead or buried cables at high voltages that are too high to go straight to your home or place of business. The transformer, or a group of transformers, lowers the voltage to a level appropriate for use in homes and businesses.
Many factors, including lightning strikes, overloading, wear and corrosion, power surges, moisture, and others, can cause transformer explosions. Transformers are equipped with safety circuits that are meant to cut the power if the voltage surges, but because they can take up to 60 milliseconds to activate, they might not be quick enough to stop the transformer from blowing. Any homes or businesses connected to the transformer experience an interruption in electrical service when a transformer blows, necessitating repair before service can be resumed.
Losing Electricity on The Way
Long-distance electricity transmission results in energy losses from power cables, transformers, overhead lines, and conductors. They result from 3 separate causes:
- The Joule effect, where energy is lost as heat in the conductor (a copper wire, for instance)
- Magnetic loss: energy dissipates in metallic parts penetrated by magnetic fields
- The dielectric effect, where energy is absorbed by the insulating material
According to the kind and ratings of the transformer, losses in overhead lines and power cables range between 1% and 2% and are primarily caused by the Joule effect. A 1% reduction in the electrical energy produced by a 1000 MW power plant translates into an extra 10 MW available for consumers, which is enough to power an additional 1,000–2,000 houses.
Electricity distributors must typically lower the voltage of the power flowing through the transmission system before delivering it to a home or place of business. Transformers "step down" the power, specifically the voltage level, transmitted over transmission lines and deliver it to distribution lines, which are then connected to homes and businesses.
