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Produced from fossil fuels, nuclear fuels and renewable energy sources, electricity can be sent over long distances from power plants through transmission line with minimal loss.
The modern power grid is based on alternate current (AC) because it allows for electricity to be transformed from high voltage to low voltage and back again.
At a power plant, a transformer increases the voltage of generated power by thousands of volts so it can be sent of long distances through high-voltage transmission power lines. Transmission lines are bundles of wires, known as conductors, that ship electric power from power plants to distant substations. At substations, transformers lower the voltage of incoming power to make it acceptable for high-volume delivery to nearby end-users. Distribution lines take this lower-voltage power to users, including households and companies. The kind of transmission infrastructure put into place is based on factors in the route of transmission, including landscape and pre-existing infrastructure.
Power authorities monitor the power grid around the clock with the goal of keeping the electric grid stable. These 'balancing authorities' ensure the electric supply meets real-time demand. Because electricity cannot be cost-effectively stored on a large scale, balancing authorities depend on power generators to react to shifts in demand as soon as possible. This can be quite challenging, as demand fluctuates significantly during the day.
Line Losses
Electricity is sent at extremely high voltage because it limits so-called line losses. Even materials that happen to be very good conductors of electricity offer some degree of resistance to its flow, and this resistance becomes considerable over long distances.
As electricity leaves a power facility, it is normally stepped up to around 69,000 to 765,000 volts. By comparison, typical voltage in the home is between 120 and 240 volts. Power losses increase with the square of a wire’s current. Therefore, keeping voltage high helps to mitigate power losses.
While technological developments have minimized loss in the system, approximately 5 percent of electricity is shed during transmission and distribution. High-voltage transmission lines are much more efficient than short-distance distribution lines.
Minimizing Losses
There are currently a number of possibilities for improving minimizing power loss in the grid, with market and political realities making some approaches more possible than others.
While superconducting materials are capable of conducting without resistance, they must be kept extremely cold, nearly absolute zero, and this requirement makes standard superconducting materials impractical for transmission lines.
However, recent advances in superconducting materials have decreased cooling requirements. In fact, a city in Germany recently installed a nearly 1-kilometer superconducting cable connecting two large transformers that was cooled by liquid nitrogen. Besides to virtually eliminating line loss, the cable was capable of sending five times more electricity than conventional cable. Superconducting cables like the one in Germany could also get rid of the need to step up voltages, making costly transformers no longer necessary.
Another option could be the use of high-voltage direct current (DC) transmission lines, which can provide higher efficiencies over alternating current (AC) lines. This is a high-cost approach that is most viable for long-distance transmission.
Flexible AC Transmission Systems (FACTS) can help improve the efficiency of existing power line by sustaining the correct voltage limits. This technology modifies quantity of power put into or absorbed by the power system.
These transmission systems permit AC lines to accept a higher power load, boost the dependability of transmission and help prevent power oscillations. These systems need new management technologies, but do not need any modifications of the current distribution system.
Sources and Further Reading
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