Transmission lines Services

Types of Transmission Lines

Transmission lines are structures or cables designed to transmit electromagnetic waves. They can be categorized into different types, depending on their length, such as underground lines and sub-transmission lines. Below, we will discuss the different types of transmission lines. These can be underground, coaxial cable, and two-wire lines. To understand which type of transmission line is best for you, we will look at the advantages and disadvantages of each. In addition, we will also look at their types.

Two-wire transmission lines

Two-wire transmission lines have two wires that are separated by about 2 to 6 inches. They are commonly used for rural telephone and telegraph lines and sometimes for connecting a television antenna to a home television. The disadvantages of this type of transmission line include high radiation losses and the lack of shielding. They can only transmit signals up to about half a kilometer without breaking down due to the change in field of each conductor.

The electrical characteristics of two-wire transmission lines depend on the construction of the line. Each type of transmission line has a conductance value, which is a measure of the current passing through the insulation. Depending on the frequency and size of the lines, capacitive reactance varies accordingly. Moreover, long conductors exhibit magnetic fields when electrical energy passes through them. Inductance values vary with the frequency. The values of inductance are obtained by analyzing the inductance of two-wire transmission lines, including balun networks.

The characteristic impedance of a two-wire transmission line is a function of the length of the lines and their respective terminations. This characteristic impedance is called the characteristic impedance (CI) and is the same for all types of transmission lines. They are used to transmit electrical signals in different applications such as telephones and computers. They are also popular for other applications, such as cellular phone towers. They can transmit signals up to 750 MHz.

The ohmic losses of two-wire transmission lines are lower than those of coax, but they increase propagation loss when they interact with other materials, such as metallic parts. Furthermore, dielectric materials can also increase the loss of surface wave propagation. The loss of reflected waves is much lower when the conductors are uniformly shielded. Despite the advantages, there are still several drawbacks to two-wire transmission lines.

In theory, a two-wire transmission line consists of two wires of equal radius r, located at a distance of D meters. The cross section of these two conductors is shown in the figure below. Moreover, two-wire transmission lines are commonly used in telephones in homes and offices, where two-wire circuits connect the local switching center. Therefore, two-wire transmission lines are widely used in the power industry.

Coaxial cable lines

Coaxial cable transmission lines have a series of properties that make them ideal for transmitting electromagnetic waves. These properties include physical size, frequency performance, attenuation, power handling, flexibility, strength, environmental conditions, cost, and jacket material. These characteristics are often optimized by optimizing a certain feature, but boosting performance in one area often leads to a degradation of performance in another. Here, we examine the key characteristics of coaxial cable transmission lines and discuss how to match a coaxial cable transmission line with the application.

The velocity factor is the difference between the wave velocity of the transmission line and that of the air that surrounds it. It is calculated by dividing the wave velocity of the transmission line by the vacuum velocity. The velocity factor is largely dependent on the type of dielectric material used in the transmission line. For example, a 1/4-wavelength coaxial cable transmission line made of solid polyethylene has a velocity factor of 0.66, which means it will have a physical length of 3.5 meters.

The new wideband nondigital transmission system utilizes coaxial cable transmission lines to carry signals. The system is compared with existing transmission systems to explore the potential of expanding the capacity to very wideband performance. It is possible to accept two-way transmission over a link consisting of 10,800 VF channels, with each coaxial subcable carrying one television channel. The coaxial cable transmission line has a number of advantages over its predecessors.

In addition to preventing interference, coaxial cable can also filter out unequal currents, making it a good choice for transmitting strong electrical signals. This cable also prevents signal coupling from adjacent structures. Its larger diameter and multiple shields ensure that the signal does not leak. And while there are some disadvantages to coaxial cable, it is an excellent choice for transmitting high-quality signals. In addition to its numerous benefits, coaxial cable transmission lines are extremely safe to use.

The inner conductor of coaxial cable can be made of solid plastic, foam plastic, or air. The dielectric properties of the insulator determine the electrical properties of the cable. Typically, the insulator is solid polyethylene, with a Teflon insulator for higher-end cables. Some coaxial cable transmission lines also utilize air or a gas instead of solid polyethylene. Regardless of insulator, the shield and splices should be properly connected to one another so that they can maintain the signal.

Underground lines

Electricity is often transported and distributed through overhead power lines. Overhead power lines are uninsulated electrical cables suspended from poles or towers. But they are vulnerable to lightning and other types of weather. Underground transmission lines, on the other hand, are protected from such elements. In addition to underground transmission lines, there are many advantages to overhead lines. They are cheaper and less intrusive than underground power lines. The following are a few of them.

First, they're much easier to maintain. Underground transmission lines can be repaired in a fraction of the time it takes overhead cables to repair them. The typical underground line outage lasts five to nine days. However, repair time for faults in overhead conductors and cross-linked polyethylene (XLPE) cable can be a matter of hours or days. For those who have a hard time waiting for repairs, there are other methods available.

Overhead transmission lines can be sited above or beneath roads. This allows them to cross rivers and motorways. Although overhead lines are cheaper to build and maintain, they can also cause visual pollution in areas they traverse. They also face threats from vandalism, lightning, and terrorism. They may also interfere with low-flying aircraft and even drones. Besides these disadvantages, overhead lines are not an ideal solution for every application.

In October 2017, the North Bay fires in California destroyed 650 miles of utility lines. Among these, 118 miles of those are underground. Most of those were installed as part of new subdivision developments. The resulting damage would cost tens of millions of dollars. However, some utilities are moving faster than others. In San Diego, for example, 60 percent of their lines are underground. And the city has set up a funding system to encourage undergrounding. If the entire California utility system were moved underground, it would take about 1,000 years.

As compared to overhead transmission lines, underground transmission lines require more land disturbance. While overhead lines disturb soil only at transmission pole locations, underground lines require extensive land disturbance and trenching. They require clearing of trees and bushes. Compared to overhead lines, underground transmission lines are less likely to lead to aesthetic problems, EMF concerns, and other post-construction concerns. However, underground cables may not be as secure as overhead ones. If you are considering installing one of these lines in your city, it is important to understand the pros and cons of the different types.

Subtransmission lines

Transmission lines carry electricity between substations and major distribution substations. Subtransmission lines typically carry voltages ranging from 34.5 kV to 69 kV and are used for industrial and large commercial operations. They are commonly overhead, but they can also be underground. Generally, subtransmission lines are smaller in length than distribution lines, and require fewer right-of-way. In urban areas, buried cable is used.

The three types of transmission lines are classified based on length and voltage. Short lines are typically less than 50 km in length and have a maximum voltage of twenty kV. They usually use lumped line constants such as resistance and inductance. Medium and long lines allow voltages of up to 100 kV, but are often larger and longer than 150 km. They are considered lossless lines. When describing a transmission line, it's important to note that the two types of lines have different characteristics.

In transmission lines, the two main types are high-voltage and low-voltage lines. Substations convert high-voltage electricity into lower-voltage electricity. Distribution lines, on the other hand, transmit electricity from the substations to consumers. These lines must be kept in good condition for long-term operations. Keeping your transmission lines clean will help avoid any downtime or loss of power. If they're shorted, they can cause major damage to property.