#Basic #Electrical #Destinations Basic Electrical Destinations Static Wire The static wire is the poles top wire which bleeds lightning surges off the power lines during a storm. Without a static wire, lightning induced voltage would otherwise build up on power line conductors during a lightning strike and cause damage. The static wire is connected to the grounding conductor. Grounding Conductor The grounding conductor is a wire that connects the static wire to the ground rod. You can recognize the grounding conductor because this wire runs the entire length of the pole. A – B – C Phase These transmission wires carry high voltage electricity from the power plants in three phases, usually labeled A, B, and C. The three phase wires carry the power to substations where the voltage is reduced. From the substations, the power is distributed by lines called feeders. Transmission Transmission wires carry electricity at voltages of 69-500 kilovolts (kV) from the generating plants to the substations. You might think of voltage as the pressure behind the electric current pushing the electricity to its destination. Supply Space Usually the upper area of the pole, the supply space is used for electric lines and other supply equipment. The National Electric Safety Code (NESC), started in 1913, sets the standards for the construction, maintenance, and safety of electric lines in the United States. Primary The primary phase conductors are part of the distribution system wires and carry electricity from the substations at 5-30 kilovolts (kV). On older poles, youll often see the primary wires supported by the crossbars. Step Down Transformer The transformer, easy to recognize by its large canister shape, converts the high primary voltage to the lower voltage needed for home use. Look closely and youll see that the high voltage transformer terminal is connected to one of the primary phase conducting wires. The transformer case is attached to the ground wire on the pole to prevent dangerous differences in voltage from developing. Multi-Grounded Neutral (MGN) Distribution lines have a grounded neutral conductor to provide a return path for the electricity. On many poles, if the distribution line is also connected to the ground wire (or grounding conductor), the line is called a multi-grounded neutral. Distribution Distribution lines carry electricity from the electric substation to homes and businesses. The power in distribution lines can be one, two, or all three phases. Secondary Service Drop – To Load The secondary service drop is the cable that brings electricity to the end user. Follow the wire from your home to the utility pole, and youll see that the secondary service drop consists of the three conductor wires. The two insulated hot wires come from the transformer, and the bare neutral wire is connected to the ground wire at the pole. The secondary lines commonly have a voltage of 120/240 V. Communication Worker Safety Zone This safety zone, also called neutral space, is the space between the lowest supply conductor or equipment and the highest communication cables or equipment. In addition to separating the high voltage lines and communications wires, the safety zone provides maneuvering room for linemen and communication workers. Communications Space Usually the lowest area on the pole, the communications space is used for cable television, broadband, and telephone wires. All attachments require the pole owners permission. Communication Lines Cable television and broadband wires are usually the uppermost communication lines. Telephone cables are often lashed to a steel strand in the lower area of the communications space. A true telephone pole supports only telephone wires, while a joint use utility pole has both electric and communications cables attached. Utility Pole Poles range from 20-100 feet tall; the standard pole is 35 feet tall. Popular pole trees include Douglas fir, Southern pine, and Western red cedar. Poles are buried about 6 feet in the ground and spaced about 125 feet apart. The wood poles lifespan is about 30-40 years. Sounding, drilling, and coring inspections give information about the poles condition. Attachment weight, moisture content, vibration, and settling add stress to poles. Utility poles may also be made of concrete, steel, or a fiberglass composite. Vegetation All plants and trees planted around poles and under wires should be trimmed regularly to avoid interference with the electric system, especially during a storm. Utility companies are responsible for pruning vegetation on their easements, and homeowners can plant smaller bushes and trees that will stay below the overhead lines. Ground Rod The ground rod is buried in the soil near the base of the utility pole. Since the ground rod is connected to the grounding conductor, when lightning strikes a pole or static wire, the high voltage surge travels down the grounding wire to the ground rod and safely into the earth. For More: Join our blog: electricaltechnology.org/
Posted on: Sun, 20 Jul 2014 11:00:00 +0000
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