隨(sui)(sui)著地區負荷變(bian)(bian)化，如果沒有(you)(you)配置(zhi)有(you)(you)載調壓(ya)(ya)變(bian)(bian)壓(ya)(ya)器，供電母(mu)線電壓(ya)(ya)將隨(sui)(sui)之變(bian)(bian)化。因此，我國《電力(li)系統技術導(dao)則(試行(xing))》規定(ding)了(le)"對110kV及(ji)以(yi)下變(bian)(bian)壓(ya)(ya)器，宜考慮至(zhi)少有(you)(you)一級電壓(ya)(ya)的變(bian)(bian)壓(ya)(ya)器采用帶負載調壓(ya)(ya)方式"。

因此，對(dui)直接(jie)向(xiang)供電(dian)(dian)(dian)中(zhong)心供電(dian)(dian)(dian)的(de)有(you)載調壓(ya)(ya)(ya)變(bian)壓(ya)(ya)(ya)器(qi)，在實現無功功率分(fen)區就地平衡的(de)前提下，隨著地區負荷(he)增減(jian)變(bian)化，配(pei)合無功補償(chang)設備并聯電(dian)(dian)(dian)容器(qi)及低壓(ya)(ya)(ya)電(dian)(dian)(dian)抗器(qi)的(de)投切，調整分(fen)接(jie)頭，以便隨時保證對(dui)用戶的(de)供電(dian)(dian)(dian)電(dian)(dian)(dian)壓(ya)(ya)(ya)質(zhi)量。

變(bian)壓(ya)器(qi)由鐵芯(xin)（或磁芯(xin)）和線(xian)(xian)圈組成，線(xian)(xian)圈有兩個(ge)(ge)或兩個(ge)(ge)以上(shang)的繞組，其中接(jie)電源的繞組叫初級(ji)線(xian)(xian)圈，其余(yu)的繞組叫次級(ji)線(xian)(xian)圈。它可(ke)以變(bian)換(huan)交流(liu)電壓(ya)、電流(liu)和阻抗。簡(jian)單的鐵心(xin)變(bian)壓(ya)器(qi)由一個(ge)(ge)軟磁材(cai)料做成的鐵心(xin)及套(tao)在(zai)鐵心(xin)上(shang)的兩個(ge)(ge)匝數不等的線(xian)(xian)圈構成。

鐵心(xin)的(de)(de)作用是(shi)(shi)加強(qiang)兩(liang)個(ge)線(xian)(xian)(xian)圈(quan)(quan)(quan)(quan)(quan)(quan)(quan)間的(de)(de)磁(ci)耦合(he)。為了減少鐵內渦流(liu)和磁(ci)滯損(sun)耗，鐵心(xin)由(you)涂漆的(de)(de)硅鋼片(pian)疊壓(ya)而成;兩(liang)個(ge)線(xian)(xian)(xian)圈(quan)(quan)(quan)(quan)(quan)(quan)(quan)之(zhi)間沒有電(dian)的(de)(de)聯系，線(xian)(xian)(xian)圈(quan)(quan)(quan)(quan)(quan)(quan)(quan)由(you)絕(jue)緣銅(tong)線(xian)(xian)(xian)（或鋁(lv)線(xian)(xian)(xian)）繞(rao)成。一(yi)個(ge)線(xian)(xian)(xian)圈(quan)(quan)(quan)(quan)(quan)(quan)(quan)接交流(liu)電(dian)源(yuan)稱(cheng)(cheng)為初級(ji)線(xian)(xian)(xian)圈(quan)(quan)(quan)(quan)(quan)(quan)(quan)（或原線(xian)(xian)(xian)圈(quan)(quan)(quan)(quan)(quan)(quan)(quan)），另一(yi)個(ge)線(xian)(xian)(xian)圈(quan)(quan)(quan)(quan)(quan)(quan)(quan)接用電(dian)器稱(cheng)(cheng)為次級(ji)線(xian)(xian)(xian)圈(quan)(quan)(quan)(quan)(quan)(quan)(quan)（或副(fu)線(xian)(xian)(xian)圈(quan)(quan)(quan)(quan)(quan)(quan)(quan)）。實(shi)際的(de)(de)變(bian)壓(ya)器是(shi)(shi)很復雜的(de)(de)，不可避免地存在銅(tong)損(sun)（線(xian)(xian)(xian)圈(quan)(quan)(quan)(quan)(quan)(quan)(quan)電(dian)阻發(fa)熱）、鐵損(sun)（鐵心(xin)發(fa)熱）和漏磁(ci)（經(jing)空(kong)氣閉合(he)的(de)(de)磁(ci)感應線(xian)(xian)(xian)）等，為了簡(jian)化討論(lun)這里只介紹理想變(bian)壓(ya)器。理想變(bian)壓(ya)器成立的(de)(de)條件是(shi)(shi)：忽略漏磁(ci)通，忽略原、副(fu)線(xian)(xian)(xian)圈(quan)(quan)(quan)(quan)(quan)(quan)(quan)的(de)(de)電(dian)阻，忽略鐵心(xin)的(de)(de)損(sun)耗，忽略空(kong)載電(dian)流(liu)（副(fu)線(xian)(xian)(xian)圈(quan)(quan)(quan)(quan)(quan)(quan)(quan)開路原線(xian)(xian)(xian)圈(quan)(quan)(quan)(quan)(quan)(quan)(quan)線(xian)(xian)(xian)圈(quan)(quan)(quan)(quan)(quan)(quan)(quan)中的(de)(de)電(dian)流(liu)）。例如電(dian)力變(bian)壓(ya)器在滿載運行時（副(fu)線(xian)(xian)(xian)圈(quan)(quan)(quan)(quan)(quan)(quan)(quan)輸出額定功率）即(ji)接近(jin)理想變(bian)壓(ya)器情(qing)況。