【正文】 direction. When a 。kV depending on the size of the area served and the practices of the local utility.The feeders run along streets overhead (or underground, in some cases) and power the distribution transformers at or near the customer premises.In addition to transforming voltage, distribution substations also isolate faults in either the transmission or distribution systems. Distribution substations are typically the points of voltage regulation, although on long distribution circuits (of several miles/kilometers), voltage regulation equipment may also be installed along the line.The downtown areas of large cities feature plicated distribution substations, with highvoltage switching, and switching and backup systems on the lowvoltage side. More typical distribution substations have a switch, one transformer, and minimal facilities on the lowvoltage side.DesignThe main issues facing a power engineer are reliability and cost. A good design attempts to strike a balance between these two, to achieve sufficient reliability without excessive cost. The design should also allow expansion of the station, when required.Selection of the location of a substation must consider many factors. Sufficient land area is required for installation of equipment with necessary clearances for electrical safety, and for access to maintain large apparatus such as transformers. Where land is costly, such as in urban areas, gas insulated switchgear may save money overall. The site must have room for expansion due to load growth or planned transmission additions. Environmental effects of the substation must be considered, such as drainage, noise and road traffic effects. A grounding (earthing) system must be designed, and ground potential rise must be calculated to protect passersby during a shortcircuit in the transmission system. The substation site must be reasonably central to the distribution area to be served.The first step in planning a substation layout is the preparation of a oneline diagram which shows in simplified form the switching and protection arrangement required, as well as the ining supply lines and outgoing feeders or transmission lines. It is a usual practice by many electrical utilities to prepare oneline diagrams with principal elements (lines, switches, circuit breakers, transformers) arranged on the page similarly to the way the apparatus would be laid out in the actual station.In a mon design, ining lines have a disconnect switch and a circuit breaker. In some cases, the lines will not have both, with either a switch or a circuit breaker being all that is considered necessary. A disconnect switch is used to provide isolation, since it cannot interrupt load current. A circuit breaker is used as a protection device to interrupt fault currents automatically, and may be used to switch loads on and off, or to cut off a line when power is flowing in the 39。kV, or whatever is mon in the area. The output is a number of feeders. Distribution voltages are typically medium voltage, between s feet。Electrical substationA substation is a part of an electrical generation, transmission, and distribution system. Substations transform voltage from high to low, or the reverse, or perform any of several other important functions. Electric power may flow through several substations between generating plant and consumer, and its voltage may change in several steps.Substations may be owned and operated by a transmission or generation electrical utility, or may be owned by a large industrial or mercial customer. Generally substations are unattended, relying on SCADA for remote supervision and control.A substation may include transformers to change voltage levels between high transmission voltages and lower distribution voltages, or at the interconnection of two different transmission voltages. The word substation es from the days before the distribution system became a grid. As central generation stations became larger, smaller generating plants were converted to distribution stations, receiving their energy supply from a larger plant instead of using their own generators. The first substations were connected to only one power station, where the generators were housed, and were subsidiaries of that power station.Elements of a substationSubstations generally have switching, protection and control equipment, and transformers. In a large substation, circuit breakers are used to interrupt any short circuits or overload currents that may occur on the network. Smaller distribution stations may use recloser circuit breakers or fuses for protection of distribution circuits. Substations themselves do not usually have generators, although a power plant may have a substation nearby. Other devices such as capacitors and voltage regulators may also be located at a substation.Substations may be on the surface in fenced enclosures, underground, or located in specialpurpose buildings. Highrise buildings may have several indoor substations. Indoor substations are usually found in urban areas to reduce the noise from the transformers, for reasons of appearance, or to protect switchgear from extreme climate or pollution conditions.Where a substation has a metallic fence, it must be properly grounded (UK: earthed) to protect people from high voltages that may occur during a fault in the network. Earth faults at a substation can cause a ground potential rise. Currents flowing in the Earth39。本篇論文在老師指導下，經(jīng)過多次修改，補充，現(xiàn)已成稿。無論在設計中的遇到什么樣的問題，老師們都給了我們最耐心、最詳細的講解，并提出了許多寶貴的意見和建議。在整個設計過程中，您不僅嚴格要求我，還在我的設計遇到困難時及時的幫助我解決問題，并傳授我各種寶貴的經(jīng)驗，使得我的設計可以順利的進行。參考文獻[1]黃純?nèi)A 工廠供電 天津大學出版社 [2]周澤存 高電壓技術 中國電力出版社 [3]姚春球 發(fā)電廠電氣部分 中國電力出版社 [4]尹克寧 電力工程 中國電力出版社 [5]方向輝 中低壓配電網(wǎng)規(guī)劃與設計基礎 中國水利水電出版社 [6]周武仲 中低壓配電設備選型與使用200例 中國電力出版社 [7]魏光耀 國際電力 中