外文翻译--无人值班变电站与变电站自动化.doc

本科毕业设计（论文） 中英文对照翻译 院（系部） 电气工程与自动化学院 专业名称 电气工程及其自动化 年级班级　 学生姓名　 指导老师 王 Unattended substation and substation automation The development of automatic reclosing made the unattended substation practical .Automatic operation ,without the continuous presence of an attendant(operator),was first tried on the synchronous converter substations supplying an interurban electric railway in 1914.In the early 1920s,the development of automatic reclosing ,protective relays ,and means for automatic control of voltage made it possible for ac substations to be completely automatic .During the period when the substations had to be controlled manually ,it was necessary that they handle enough power to justify the operator`s wages .This dictated large stations ,frequently serving large areas by means of many feeders .The feeders that served the more distant parts of an area had to go a long way before they picked up any load .Furthermore ,as the load on a large substation grows ,transformer capacity has to be added .This increases the short-circuit current on the secondary side sometimes the short-circuit capacity exceeds the interrupting capacity of the circuit breakers already installed .Appropriate remedies include bus sectionalizing ,the installation of reactors or some combination of the two .Such measures are frequently expensive and inconvenient and they constitute an undesirable limitation on operating flexibility. Once the unattended substation became a reality ,the substation could be made smaller .Located nearer the load ,and long feeders were no longer necessary .This new method of distribution had become available since load growth could now be accommodated by installing another substation that could carry parts of the area loads formerly carried by adjacent substations .Usually ,there is no interconnection between the circuits energized by the various substations .Consequently ,ther