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A transmission grid is a network of power stations, transmission lines, and substations. Energy is usually transmitted within a grid with three-phase AC. 100 feet of 12 gauge wire delivering 15 amps of current, for example, wastes 77 watts of energy. Smaller diameter wire takes longer to transfer electrons than bigger diameter wire. High-voltage direct current (HVDC) systems require relatively costly conversion equipment that may be economically justified for particular projects such as submarine cables and longer distance high capacity point-to-point transmission. In the United States, power transmission is, variously, 230 kV to 500 kV, with less than 230 kV or more than 500 kV as exceptions. Higher order phase systems require more than three wires, but deliver little or no benefit. Current flowing through transmission lines induces a magnetic field that surrounds the lines of each phase and affects the inductance of the surrounding conductors of other phases. Transmission efficiency is improved at higher voltage and lower current. Substation transformers reduce the voltage to a lower level for distribution to customers. Subtransmission runs at relatively lower voltages. As power systems evolved, voltages formerly used for transmission were used for subtransmission, and subtransmission voltages became distribution voltages. For transmission systems with low power factor, losses are higher than for systems with high power factor.

The voltage, power, frequency, load factor, and reliability capabilities of the transmission system are designed to provide cost effective performance. Many countries regulate transmission separately from generation. In voltage signaling, voltage is varied to increase generation. Typically, only larger substations connect with this high voltage. Loops can be normally closed, where loss of one circuit should result in no interruption, or normally open where substations can switch to a backup supply. It is uneconomical to connect all distribution substations to the high main transmission voltage, because that equipment is larger and more expensive. As of 1980, the longest cost-effective distance for DC transmission was 7,000 kilometres (4,300 miles). For AC it was 4,000 kilometres (2,500 miles), though US transmission lines are substantially shorter. In general, losses are estimated from the discrepancy between power produced (as reported by power plants) and power sold; the difference constitutes transmission and distribution losses, assuming no utility theft occurs. Joule's first law states that energy losses are proportional to the square of the current.

Thus, reducing the current by a factor of two lowers the energy lost to conductor resistance by a factor of four for any given size of conductor. The optimum size of a conductor for a given voltage and current can be estimated by Kelvin's law for conductor size, which states that size is optimal when the annual cost of energy wasted in resistance is equal to the annual capital charges of providing the conductor. Since power lines are designed for long-term use, Kelvin's law is used in conjunction with long-term estimates of the price of copper and aluminum as well as interest rates. Because electrical signals are not 100 percent efficient, some in the information gets lost, causing slow downs with transmission rates. Coaxial design helps to further reduce low-frequency magnetic transmission and pickup. Hence, you would need to choose or select a design which you prefer. If you want to know which industry need more magnesium oxide, the electric wire and cable industry could not be ignored. So, if you want to buy wire in India, you can buy them online. Safety signage can provide information about the risks in the area.

Because of the economic benefits of load sharing, wide area transmission grids may span countries and even continents. While power loss can also be reduced by increasing the wire's conductance (by increasing its cross-sectional area), larger conductors are heavier and more expensive. And since conductance is proportional to cross-sectional area, resistive power loss is only reduced proportionally with increasing cross-sectional area, providing a much smaller benefit than the squared reduction provided by multiplying the voltage. To avoid stuff like these from occurring, voltage converters are utilized, and buying a great current converter could be important for individuals who travel to different places constantly. For a given amount of power, a higher voltage reduces the current and thus the resistive losses. The reduced current reduces heating losses. The NF C 15-100 standard defines a conductor cross-section (in mm²) for each specific requirement adapted to the current intensity (in Amperes) that the circuit must support.

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