是把一些(xie)設備組裝起來，用以切斷或接通、改變或者(zhe)調整電壓。在電力系統(tong)中，變電站(zhan)是輸電和配(pei)電的集結點。變電站(zhan)主(zhu)要分(fen)為：升壓變電站(zhan)，主(zhu)網變電站(zhan)，二次(ci)變電站(zhan)，配(pei)電站(zhan)。

預裝式變電站（歐(ou)式箱變）

　　變(bian)(bian)(bian)(bian)電(dian)(dian)站(zhan)是電(dian)(dian)力(li)系(xi)統中變(bian)(bian)(bian)(bian)換(huan)電(dian)(dian)壓、接(jie)受(shou)和分配(pei)電(dian)(dian)能(neng)、控制(zhi)電(dian)(dian)力(li)的(de)流向(xiang)和調(diao)整(zheng)電(dian)(dian)壓的(de)電(dian)(dian)力(li)設(she)施，它通過其變(bian)(bian)(bian)(bian)壓器將各級電(dian)(dian)壓的(de)電(dian)(dian)網(wang)聯系(xi)起來(lai)。變(bian)(bian)(bian)(bian)電(dian)(dian)站(zhan)起變(bian)(bian)(bian)(bian)換(huan)電(dian)(dian)壓作用(yong)的(de)設(she)備是變(bian)(bian)(bian)(bian)壓器，除此(ci)之外，變(bian)(bian)(bian)(bian)電(dian)(dian)站(zhan)的(de)設(she)備還(huan)有開閉電(dian)(dian)路的(de)開關(guan)設(she)備，匯集(ji)電(dian)(dian)流的(de)母線，計量和控制(zhi)用(yong)互感器、儀表(biao)、繼(ji)電(dian)(dian)保(bao)護裝(zhuang)置(zhi)和防(fang)雷保(bao)護裝(zhuang)置(zhi)、調(diao)度通信裝(zhuang)置(zhi)等，有的(de)變(bian)(bian)(bian)(bian)電(dian)(dian)站(zhan)還(huan)有無功補償設(she)備。

　　變(bian)電(dian)站的主要設備和連接方(fang)式(shi)，按其功能不同而(er)有差異。變(bian)壓器是變(bian)電(dian)站的主要設備，分(fen)為雙(shuang)繞(rao)(rao)(rao)組(zu)(zu)(zu)變(bian)壓器、三繞(rao)(rao)(rao)組(zu)(zu)(zu)變(bian)壓器和自耦變(bian)壓器即高(gao)、低壓每相(xiang)共用一(yi)個繞(rao)(rao)(rao)組(zu)(zu)(zu)，從(cong)高(gao)壓繞(rao)(rao)(rao)組(zu)(zu)(zu)中間(jian)抽出(chu)一(yi)個頭作為低壓繞(rao)(rao)(rao)組(zu)(zu)(zu)的出(chu)線(xian)的變(bian)壓器。電(dian)壓高(gao)低與繞(rao)(rao)(rao)組(zu)(zu)(zu)匝(za)數成正比，電(dian)流(liu)則與繞(rao)(rao)(rao)組(zu)(zu)(zu)匝(za)數成反(fan)比。

　　變(bian)(bian)(bian)壓(ya)(ya)(ya)(ya)器(qi)按(an)其(qi)作用可分(fen)為(wei)升壓(ya)(ya)(ya)(ya)變(bian)(bian)(bian)壓(ya)(ya)(ya)(ya)器(qi)和降壓(ya)(ya)(ya)(ya)變(bian)(bian)(bian)壓(ya)(ya)(ya)(ya)器(qi)。前者(zhe)用于電(dian)力(li)系統送端變(bian)(bian)(bian)電(dian)站，后(hou)者(zhe)用于受端變(bian)(bian)(bian)電(dian)站。變(bian)(bian)(bian)壓(ya)(ya)(ya)(ya)器(qi)的(de)電(dian)壓(ya)(ya)(ya)(ya)需與(yu)電(dian)力(li)系統的(de)電(dian)壓(ya)(ya)(ya)(ya)相適應。為(wei)了在不(bu)同負荷(he)情況下保持合格(ge)的(de)電(dian)壓(ya)(ya)(ya)(ya)有(you)(you)時需要切換變(bian)(bian)(bian)壓(ya)(ya)(ya)(ya)器(qi)的(de)分(fen)接頭(tou)。按(an)分(fen)接頭(tou)切換方式變(bian)(bian)(bian)壓(ya)(ya)(ya)(ya)器(qi)有(you)(you)帶(dai)負荷(he)有(you)(you)載(zai)調壓(ya)(ya)(ya)(ya)變(bian)(bian)(bian)壓(ya)(ya)(ya)(ya)器(qi)和無負荷(he)無載(zai)調壓(ya)(ya)(ya)(ya)變(bian)(bian)(bian)壓(ya)(ya)(ya)(ya)器(qi)。