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One feature of Romex is that it includes SIMpull, a slippery coating on the sheathing that reduces friction when pulling the cable through studs and other difficult passages. Once cut, NM cable is easy to rip (lengthwise) since the sheathing is plastic, what is electric cable not metal. NM wire is in contrast to metallic sheathed cable, sometimes called BX cable, in which the bundle of individual wires is protected by metal sheathing. As required by electrical codes, the wire gauges and the metallic content will be the same. Though armored cable can be installed in an exposed manner without the use of conduit, many installers opt to use conduit anyway if the wire will be in plain view, as the conduit makes for a much neater visual than the loose armored cable. Widespread use of such motors were delayed many years by development problems and the scarcity of polyphase power systems needed to power them. These included single phase AC systems, poly-phase AC systems, low voltage incandescent lighting, high-voltage arc lighting, and existing DC motors in factories and street cars. These were induction motors running on polyphase current, independently invented by Galileo Ferraris and Nikola Tesla. Cooke, W.F., The Electric Telegraph, Was it invented by Prof. Wheatstone?

Commercial electric power was initially transmitted at the same voltage used by lighting and mechanical loads. This means that they burn less gas to supply hot water to something like a sink than they would if you are using multiple fixtures at the same time. 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. Oscillatory motion of the physical line is termed conductor gallop or flutter depending on the frequency and amplitude of oscillation. The center of the conductor carries little current but contributes weight and cost. Underground power transmission has a significantly higher installation cost and greater operational limitations, but lowers maintenance costs. Cable and excavation costs are much higher than overhead construction. This extends the repair period and increases costs. The temperature of the pipe and surroundings are monitored throughout the repair period.

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 technology contains liquid electrolyte in an unsealed container, requiring that the battery be kept upright and the area be well ventilated to ensure safe dispersal of the hydrogen gas it produces during overcharging. NM cable usually contains one or more "hot" (current-carrying) wires, a neutral wire, and a ground wire. It is uneconomical to connect all distribution substations to the high main transmission voltage, because that equipment is larger and more expensive. A transmission grid is a network of power stations, transmission lines, and substations. These are generally used in airports, radio stations, for some heavy industrial purpose. Today, transmission-level voltages are usually 110 kV and above. Electricity is transmitted at high voltages to reduce the energy loss due to resistance that occurs over long distances.

Transmission voltages increased throughout the 20th century. In the 19th century and early 20th century, electrical cable was often insulated using cloth, rubber or paper. Yates, JoAnne. The Telegraph's Effect on Nineteenth Century Markets and Firms, Massachusetts Institute of Technology, pp. Working with the support of George Westinghouse, in 1886 he demonstrated a transformer-based AC lighting system in Great Barrington, Massachusetts. But, they must be mechanically stronger because they are suspended from the poles/towers, and they must support their own weight, for which they must withstand great tension. When these products have to go to high fire to meet a large demand you must be able to provide enough gas for the unit to function properly. A sophisticated control system is required to ensure that power generation closely matches demand. If demand exceeds supply, the imbalance can cause generation plant(s) and transmission equipment to automatically disconnect or shut down to prevent damage.