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<br />1~'~ l <br /> <br />CONSTRUCTION UTILITIES <br /> <br />133 <br /> <br />a single 33-kv line extends to the Colorado River, constituting the <br />only source of power supply along this portion of the aqueduct. <br />The 33-kv line west of the Granite substation is normally sec- <br />tionalized between substations so that it operates on the radial <br />feeder principle. However, during outages of any section of the <br />66-kv line it is possible to make an emergency by-pass by tying <br />together the 33-kv distribution feeder lines. <br /> <br />,) \ <br /> <br /> <br />LOS ANGELES <br />. <br /> <br />""" ' <br />\~~ <br />~~~1 <br /> <br />C!: <br />" <br /> <br />SCALE <br /> <br />Fig. JO--Con.'ltruction power system <br /> <br />On June 17, 1937 a duplicate power circuit was established from <br />Iron Mountain to Camino station and thence to the Colorado River <br />through the District's newly constructed Boulder transmission line, <br />which had not yet been energized from the Boulder Canyon plant. <br />At this time the Reclamation Bureau contractor, nearing comple- <br />tion of excavation for Parker dam, was encountering a large inflow <br />of water through the river gravels. A power outage of any consid- <br />erable duration during this period 011 the single 33-kv line from <br />the Granite substation might have had extremely serious conse- <br />Quences and this use of the Boulder line added greatly to the safety <br />of his operations. <br />In the construction of the transmission lines butt-treated cedar <br />and full-treated fir poles were used. The 66-kv lines are of H- <br />frame and wooden wishbone construction, the design being varied <br />to meet the different topographic conditions encountered. The <br />H-frame type predominates. Suspension-type insulators are used, <br />carrying No. 4/0 copper conductor. The total length of 66-kv line <br />is 196 miles. In the 33-kv lines single pole, flat construction is <br />typical, but use is made of the H-frame when necessary and joint <br />construction with 66-kv lines where permissible. The 33-kv dis- <br />