How Do Power Lines Work?

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Electricity is delivered to homes, schools, hospitals, businesses and industries through an integrated system of power plants, power lines and substations. Transmission lines consist of heavy-duty cables wound between tall towers that carry electricity from where it is generated to where it is needed. Transmission networks allow for the transmission of large amounts of electricity over long distances.

Power systems involve the generation, transmission and distribution of electricity. As the demand for electricity grew and small power plants that could only serve local areas became inadequate, the need for high-capacity transmission arose. Newer, larger power plants come online, but far from load centers. Transmission lines were the only way to get power to where it was needed.

Most long-distance power lines do not use insulation around the conductors themselves. Insulation in this way must be so thick that it is not cost effective. Instead, most of the insulation comes from the air gap, or just spacing everything far enough apart.

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Transmission towers and pylons are very high to prevent anyone on the ground or any vehicle from inadvertently coming close enough to the conductors to create an arc. High-capacity power is transmitted in three phases, which is why you will see most transmission conductors in groups of three. Each phase is far enough away from the other two to avoid arcing between the phases. The conductors are connected to each tower by long insulators to maintain a sufficient distance between the energized line and the grounded tower.

These insulators are usually made of ceramic discs, so if they get wet, leakage must go through a longer grounding path. These discs are somewhat standardized, so this is an easy way to make a rough guess at the transmission line voltage. Simply multiply the number of discs by 15.

High voltage isn't the only design challenge associated with transmission lines. Conductor selection alone is a careful balance of strength, resistance and other factors. Transmission lines are so long that even small changes in conductor size or material can have a significant impact on overall cost. Conductors are rated for how much current they can pass for a given temperature rise.

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During peak electricity usage, these lines can become very hot and saggy, which can cause problems if tree branches get too close. Wind can also affect the conductors, causing oscillations that can lead to material damage or failure. You'll often see these small devices called Stockbridge dampers used to absorb some of the wind energy.

High-voltage transmission lines also generate magnetic fields that induce currents in parallel conductors such as fences and interfere with magnetic devices, so the height of towers is sometimes set to minimize EMFs at the edge of the right-of-way. in some cases, engineers even need to consider the audible noise of the transmission line so as not to disturb nearby residents.

Even with all of these factors in mind, the classic grid model of centralized power generation away from densely populated areas is changing. The cost of solar panels continues to fall, making it increasingly easy to produce some or all of the electricity you use in your own house or business, or even to export excess energy back to the grid. This type of local generation occurs on the distribution side of the grid, often skipping large transmission lines altogether.

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On the other hand, energy markets are changing, and grid operators are buying and selling power over long distances. A power transmission line may seem simple - the equivalent of an extension cord across the sky.

Founded in 1986, SAA Grid Technology Co., Ltd is a national high-tech enterprise and one of the most powerfulpolymer insulator manufacturers in China. We manufacture the following products: 110kV-1000kV polymer long rod insulators, 11kV-230kV polymer line post insulators, 11kV-800kV polymer station post insulators, 27.5kV polymer railway insulators; surge arresters, drop-out fuse cutout, disconnectors and other electrical products. Get in touch for a free quote today.

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