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It is often used as a transmission line between an antenna and a receiver (e.g., TV and radio). The transmission system usually does not have a large buffering capability to match loads with generation. All wires running inside this shielding layer will be to a large extent decoupled from external electrical fields, particularly if the shield is connected to a point of constant voltage, such as earth or ground. Simple shielding of this type is not greatly effective against low-frequency magnetic fields, however - such as magnetic "hum" from a nearby power transformer. Shielding makes use of the electrical principle of the Faraday cage. Norway and Sweden also use this frequency but use conversion from the 50 Hz public supply; Sweden has a 16 2/3 Hz traction grid but only for part of the system. One grid connects most of continental Europe. A wide area synchronous grid, known as an interconnection in North America, directly connects generators delivering AC power with the same relative frequency to many consumers. Different classes of loads (for example, lighting, fixed motors, and traction/railway systems) required different voltages, and so used different generators and circuits. Thus, generators were sited near their loads, a practice that later became known as distributed generation using large numbers of small generators.

Alternating current's economies of scale with large generating plants and long-distance transmission slowly added the ability to link all the loads. Electric power transmission is the bulk movement of electrical energy from a generating site, such as a power plant, to an electrical substation. Applications for a new transmission line typically include an analysis of electric and magnetic field levels at the edge of rights-of-way. Overhead transmission wires depend on air for insulation, requiring that lines maintain minimum clearances. High-voltage overhead conductors are not covered by insulation. A grounded shield on cables operating at 2.5 kV or more gathers leakage current and capacitive current, protecting people from electric shock and equalizing stress on the cable insulation. Often the actual cable type and size is printed right on the cable insulation. This type of cable is often used in areas with stricter rules and regulations surrounding electrical codes, where NM cables may not be allowed. In the worst case, this may lead to a cascading series of shutdowns and a major regional blackout. HVDC links stabilize power distribution networks where sudden new loads, or blackouts, in one part of a network might otherwise result in synchronization problems and cascading failures. Interconnection of local generation plants and small distribution networks was spurred by World War I, when large electrical generating plants were built by governments to power munitions factories.

These networks use components such as power lines, cables, circuit breakers, switches and transformers. It was powered by a 2 kV, 130 Hz Siemens & Halske alternator and featured several Gaulard transformers with primary windings connected in series, which fed incandescent lamps. The voltage level is changed with transformers. The highest voltage then used was 150 kV. The opinion also limited the voltage of new transmission lines built in New York to 345 kV. For AC it was 4,000 kilometres (2,500 miles), though US transmission lines are substantially shorter. Faults in buried transmission lines take longer to locate and repair. Efficient long-distance transmission of electric power requires high voltages. As a comparison with everyday items, a hair dryer or electric blanket produces a 100 mG - 500 mG magnetic field. The system proved the feasibility of AC electric power transmission over long distances. If an electric fault damages the pipe and leaks dielectric, liquid nitrogen is used to freeze portions of the pipe to enable draining and repair. This extends the repair period and increases costs.

Underground power transmission has a significantly higher installation cost and greater operational limitations, but lowers maintenance costs. In 1882, DC voltage could not easily be increased for long-distance transmission. Voltages above 765 kV are considered extra high voltage and require different designs. Electricity is transmitted at high voltages to reduce the energy loss due to resistance that occurs over long distances. 6 American wire gauge) to 750 mm2 (1,590,000 circular mils area), with varying resistance and current-carrying capacity. 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. Wind speeds as low as 23 knots (43 km/h) can permit conductors to encroach operating clearances, resulting in a flashover and loss of supply. Single-wire earth return (SWER) or single-wire ground return is a single-wire transmission line for supplying single-phase electrical power to remote areas at low cost. Adverse weather conditions, such as high winds and low temperatures, interrupt transmission. The terminal characteristics of the transmission line are the voltage and current at the sending (S) and receiving (R) ends.

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