是社會經濟發(fa)展和城市建(jian)設的(de)(de)必然(ran)產物。隨著近二十多年的(de)(de)經濟發(fa)展，城市供(gong)電(dian)(dian)的(de)(de)格局發(fa)生了較(jiao)大(da)的(de)(de)變化(hua)，過(guo)去那種集中降壓(ya)(ya)、長(chang)距離(li)配電(dian)(dian)的(de)(de)方(fang)式(shi)已經大(da)大(da)制約(yue)了城市供(gong)電(dian)(dian)，并降低了供(gong)電(dian)(dian)企業的(de)(de)經濟效(xiao)益。原因是供(gong)電(dian)(dian)半徑過(guo)大(da)，線路損耗(hao)隨著用(yong)電(dian)(dian)負荷的(de)(de)增(zeng)(zeng)加而大(da)大(da)增(zeng)(zeng)加，同時(shi)供(gong)電(dian)(dian)質(zhi)量也(ye)大(da)大(da)降低。要減少(shao)線路損耗(hao)，保證供(gong)電(dian)(dian)質(zhi)量，就得提(ti)高(gao)(gao)(gao)供(gong)電(dian)(dian)電(dian)(dian)壓(ya)(ya)，這是眾所周(zhou)知(zhi)的(de)(de)事實。為此，在城網(wang)建(jian)設中，要求高(gao)(gao)(gao)壓(ya)(ya)直接(jie)進入(ru)(ru)市區，深入(ru)(ru)負荷中心(xin)。有資料顯示，將(jiang)供(gong)電(dian)(dian)電(dian)(dian)壓(ya)(ya)從 380V上升到10kV，可以減少(shao)線路損耗(hao)60%，減少(shao)總投資和用(yong)銅(tong)量52%，其經濟效(xiao)益相(xiang)當可觀。要實現高(gao)(gao)(gao)壓(ya)(ya)深入(ru)(ru)負荷中心(xin)，箱式(shi)變電(dian)(dian)站是最經濟、方(fang)便、有效(xiao)的(de)(de)設備之一。

　　箱式(shi)(shi)(shi)變(bian)(bian)(bian)電(dian)(dian)(dian)站(zhan)，是(shi)集高(gao)壓開(kai)關柜(ju)、變(bian)(bian)(bian)壓器、低(di)壓開(kai)關柜(ju)于一(yi)體(ti)，并在制造廠內裝(zhuang)(zhuang)配完成(cheng)的(de)預(yu)裝(zhuang)(zhuang)式(shi)(shi)(shi)變(bian)(bian)(bian)電(dian)(dian)(dian)站(zhan)。由于箱變(bian)(bian)(bian)具有成(cheng)套性(xing) 強(qiang)(qiang)、體(ti)積小(xiao)(xiao)、占地少(shao)、能(neng)深入負荷中心(xin)、提高(gao)供電(dian)(dian)(dian)質量、減少(shao)線(xian)路損(sun)耗、縮短(duan)送電(dian)(dian)(dian)周期、選擇靈活(huo)、對(dui)環境適(shi)應性(xing)強(qiang)(qiang)、安(an)裝(zhuang)(zhuang)方(fang)便、運行安(an)全可靠及投資少(shao)及見效(xiao)快(kuai)等(deng)(deng)一(yi)系列優點;所以箱變(bian)(bian)(bian)有著廣闊的(de)使用(yong)范圍，它適(shi)用(yong)于城市(shi)公(gong)共配電(dian)(dian)(dian)、高(gao)層建筑、住宅小(xiao)(xiao)區、公(gong)園、高(gao)速(su)公(gong)路等(deng)(deng)，還適(shi)用(yong)于油(you)田(tian)、工礦企業及施工場所等(deng)(deng)。它是(shi)繼土建變(bian)(bian)(bian)電(dian)(dian)(dian)所之后(hou)崛起的(de)一(yi)種嶄(zhan)新的(de)變(bian)(bian)(bian)電(dian)(dian)(dian)站(zhan)，在我區的(de)住宅小(xiao)(xiao)區建設(she)中，為提高(gao)城建形象，改善居住環境，各有關部(bu)門紛紛要求(qiu)取消架(jia)空線(xian)路。對(dui)此(ci)，除廣泛采用(yong)高(gao)、低(di)壓電(dian)(dian)(dian)纜外，在城區用(yong)地十分緊張、以土建方(fang)式(shi)(shi)(shi)建造變(bian)(bian)(bian)電(dian)(dian)(dian)站(zhan)非常(chang)困難(nan)的(de)情況下，采用(yong)10kV箱式(shi)(shi)(shi)變(bian)(bian)(bian)電(dian)(dian)(dian)站(zhan)是(shi)一(yi)種優化選擇方(fang)案(an)。

一、箱式變電站型式的選擇

　　1、歐式箱變特點

　　根據產品結構不同及采(cai)用元(yuan)器件的(de)不同，箱(xiang)變分(fen)為和(he)兩種典型形式。

　　歐式箱(xiang)(xiang)變(bian)是將變(bian)壓(ya)器(qi)及普通(tong)的高(gao)壓(ya)電器(qi)設備裝于(yu)同一個金屬外殼箱(xiang)(xiang)體(ti)(ti)(ti)中，從(cong)結構上(shang)采用(yong)(yong)高(gao)、低(di)壓(ya)開(kai)關(guan)柜，變(bian)壓(ya)器(qi)組(zu)成方式，這(zhe)種箱(xiang)(xiang)變(bian)稱為(wei)歐式箱(xiang)(xiang)變(bian)，形象(xiang)比喻為(wei)給高(gao)、低(di)壓(ya)開(kai)關(guan)柜、變(bian)壓(ya)器(qi)蓋了房子。由于(yu)變(bian)壓(ya)器(qi)室溫(wen)很高(gao)，引(yin)起散熱困(kun)難，影響(xiang)出力;另一方面在箱(xiang)(xiang)體(ti)(ti)(ti)中采用(yong)(yong)普通(tong)的高(gao)壓(ya)負荷開(kai)關(guan)和熔斷器(qi)、低(di)壓(ya)開(kai)關(guan)柜，所以箱(xiang)(xiang)式變(bian)體(ti)(ti)(ti)積(ji)較(jiao)大。

　　2、美式(shi)箱變特點

　　在(zai)結(jie)構(gou)上(shang)將負(fu)荷(he)開(kai)(kai)關(guan)(guan)、環網開(kai)(kai)關(guan)(guan)和熔斷(duan)器(qi)(qi)(qi)(qi)(qi)(qi)結(jie)構(gou)簡(jian)化(hua)放入(ru)(ru)變(bian)(bian)(bian)(bian)(bian)(bian)壓(ya)(ya)(ya)(ya)(ya)器(qi)(qi)(qi)(qi)(qi)(qi)油(you)(you)(you)(you)箱(xiang)(xiang)(xiang)浸(jin)在(zai)油(you)(you)(you)(you)中(zhong)。避雷(lei)器(qi)(qi)(qi)(qi)(qi)(qi)也采用(yong)油(you)(you)(you)(you)浸(jin)式(shi)氧化(hua)鋅避雷(lei)器(qi)(qi)(qi)(qi)(qi)(qi)。變(bian)(bian)(bian)(bian)(bian)(bian)壓(ya)(ya)(ya)(ya)(ya)器(qi)(qi)(qi)(qi)(qi)(qi)取(qu)消(xiao)(xiao)油(you)(you)(you)(you)枕，油(you)(you)(you)(you)箱(xiang)(xiang)(xiang)及散(san)熱(re)器(qi)(qi)(qi)(qi)(qi)(qi)暴露在(zai)空(kong)氣中(zhong)，這(zhe)種(zhong)(zhong)箱(xiang)(xiang)(xiang)變(bian)(bian)(bian)(bian)(bian)(bian)稱為(wei)(wei)美式(shi)箱(xiang)(xiang)(xiang)變(bian)(bian)(bian)(bian)(bian)(bian)，形(xing)象比喻為(wei)(wei)變(bian)(bian)(bian)(bian)(bian)(bian)壓(ya)(ya)(ya)(ya)(ya)器(qi)(qi)(qi)(qi)(qi)(qi)旁邊掛個箱(xiang)(xiang)(xiang)子。美式(shi)箱(xiang)(xiang)(xiang)變(bian)(bian)(bian)(bian)(bian)(bian)從(cong)布(bu)置(zhi)上(shang)看(kan)，其低(di)壓(ya)(ya)(ya)(ya)(ya)室、變(bian)(bian)(bian)(bian)(bian)(bian)壓(ya)(ya)(ya)(ya)(ya)器(qi)(qi)(qi)(qi)(qi)(qi)室、高(gao)壓(ya)(ya)(ya)(ya)(ya)室不是目字型(xing)布(bu)置(zhi)，而是品字型(xing)布(bu)置(zhi)。從(cong)結(jie)構(gou)上(shang)看(kan)，這(zhe)種(zhong)(zhong)箱(xiang)(xiang)(xiang)式(shi)變(bian)(bian)(bian)(bian)(bian)(bian)分(fen)為(wei)(wei)前(qian)(qian)、后兩部分(fen)：前(qian)(qian)面為(wei)(wei)高(gao)、低(di)壓(ya)(ya)(ya)(ya)(ya)操(cao)(cao)作(zuo)間隔，操(cao)(cao)作(zuo)間隔內包(bao)括高(gao)低(di)壓(ya)(ya)(ya)(ya)(ya)接線 端子，負(fu)荷(he)開(kai)(kai)關(guan)(guan)操(cao)(cao)作(zuo)把手，無載調壓(ya)(ya)(ya)(ya)(ya)分(fen)節(jie)開(kai)(kai)關(guan)(guan)，插入(ru)(ru)式(shi)熔斷(duan)器(qi)(qi)(qi)(qi)(qi)(qi)，油(you)(you)(you)(you)位計等;后部為(wei)(wei)注油(you)(you)(you)(you)箱(xiang)(xiang)(xiang)及散(san)熱(re)片(pian)。將變(bian)(bian)(bian)(bian)(bian)(bian)壓(ya)(ya)(ya)(ya)(ya)器(qi)(qi)(qi)(qi)(qi)(qi)繞組、鐵心、高(gao)壓(ya)(ya)(ya)(ya)(ya)負(fu)荷(he)開(kai)(kai)關(guan)(guan)和熔斷(duan)器(qi)(qi)(qi)(qi)(qi)(qi)放入(ru)(ru)變(bian)(bian)(bian)(bian)(bian)(bian)壓(ya)(ya)(ya)(ya)(ya)器(qi)(qi)(qi)(qi)(qi)(qi)油(you)(you)(you)(you)箱(xiang)(xiang)(xiang)中(zhong)。避雷(lei)器(qi)(qi)(qi)(qi)(qi)(qi)也采用(yong)油(you)(you)(you)(you)浸(jin)式(shi)金屬氧化(hua)物(wu)避雷(lei)器(qi)(qi)(qi)(qi)(qi)(qi)。變(bian)(bian)(bian)(bian)(bian)(bian)壓(ya)(ya)(ya)(ya)(ya)器(qi)(qi)(qi)(qi)(qi)(qi)取(qu)消(xiao)(xiao)油(you)(you)(you)(you)枕，采取(qu)油(you)(you)(you)(you)加(jia)氣隙體積(ji)(ji)(ji)恒定(ding)原則設(she)計密封式(shi)油(you)(you)(you)(you)箱(xiang)(xiang)(xiang)，油(you)(you)(you)(you)箱(xiang)(xiang)(xiang)及散(san)熱(re)器(qi)(qi)(qi)(qi)(qi)(qi)暴露在(zai)空(kong)氣中(zhong)，散(san)熱(re)優于(yu)歐(ou)式(shi)箱(xiang)(xiang)(xiang)變(bian)(bian)(bian)(bian)(bian)(bian)。低(di)壓(ya)(ya)(ya)(ya)(ya) 斷(duan)路(lu)(lu)器(qi)(qi)(qi)(qi)(qi)(qi)采用(yong)塑(su)殼斷(duan)路(lu)(lu)器(qi)(qi)(qi)(qi)(qi)(qi)作(zuo)為(wei)(wei)主斷(duan)路(lu)(lu)器(qi)(qi)(qi)(qi)(qi)(qi)及出線斷(duan)路(lu)(lu)器(qi)(qi)(qi)(qi)(qi)(qi)。由(you)于(yu)結(jie)構(gou)簡(jian)化(hua)，這(zhe)種(zhong)(zhong)箱(xiang)(xiang)(xiang)式(shi)變(bian)(bian)(bian)(bian)(bian)(bian)電站的占地(di)面積(ji)(ji)(ji)和體積(ji)(ji)(ji)大大減小，由(you)于(yu)其體積(ji)(ji)(ji)很小再(zai)加(jia)上(shang)只是一側開(kai)(kai)門(men)，其所需占地(di)面積(ji)(ji)(ji)僅是歐(ou)式(shi)箱(xiang)(xiang)(xiang)變(bian)(bian)(bian)(bian)(bian)(bian)的1/4，體積(ji)(ji)(ji)僅為(wei)(wei)同(tong)容量歐(ou)式(shi)箱(xiang)(xiang)(xiang)變(bian)(bian)(bian)(bian)(bian)(bian)的1/5-1/3。

　　3、兩(liang)類箱變的比較

　　從保(bao)(bao)護方面，歐式(shi)箱(xiang)變(bian)高(gao)(gao)壓(ya)(ya)側(ce)采用(yong)(yong)負荷(he)(he)開(kai)(kai)關加(jia)限流(liu)熔(rong)(rong)斷器(qi)保(bao)(bao)護。發(fa)生一(yi)(yi)相(xiang)(xiang)熔(rong)(rong)斷器(qi)熔(rong)(rong)斷時(shi)，用(yong)(yong)熔(rong)(rong)斷器(qi)的(de)撞針使負荷(he)(he)開(kai)(kai)關三相(xiang)(xiang)同時(shi)分(fen)閘，避免缺相(xiang)(xiang)運行，要(yao)求負荷(he)(he)開(kai)(kai)關具有(you)切(qie)(qie)斷轉移電(dian)(dian)流(liu)能力(li)。低(di)(di)壓(ya)(ya)側(ce)采用(yong)(yong)負荷(he)(he)開(kai)(kai)關加(jia)限流(liu)熔(rong)(rong)斷器(qi)保(bao)(bao)護，美式(shi)箱(xiang)變(bian)高(gao)(gao)壓(ya)(ya)側(ce)采用(yong)(yong)熔(rong)(rong)斷器(qi)保(bao)(bao)護，而(er)負荷(he)(he)開(kai)(kai)關只起投切(qie)(qie)轉換和(he)切(qie)(qie)斷高(gao)(gao)壓(ya)(ya)負荷(he)(he)電(dian)(dian)流(liu)的(de)功能，容(rong)量較小。當高(gao)(gao)壓(ya)(ya)側(ce)出現一(yi)(yi)相(xiang)(xiang)熔(rong)(rong)絲熔(rong)(rong)斷，低(di)(di)壓(ya)(ya)側(ce)的(de)電(dian)(dian)壓(ya)(ya)就(jiu)降(jiang)低(di)(di)，塑殼自(zi)動空(kong)(kong)氣開(kai)(kai)關欠電(dian)(dian)壓(ya)(ya)保(bao)(bao)護或過電(dian)(dian)流(liu)保(bao)(bao)護就(jiu)會動作，低(di)(di)壓(ya)(ya)運行不(bu)會發(fa)生。從產品成本(ben)看，歐式(shi)箱(xiang)變(bian)成本(ben)高(gao)(gao)。從產品降(jiang)價(jia)(jia)空(kong)(kong)間看，美式(shi)箱(xiang)變(bian)還存(cun)在(zai)較大(da)降(jiang)價(jia)(jia)空(kong)(kong)間，一(yi)(yi)方面美式(shi)箱(xiang)變(bian)三相(xiang)(xiang)五柱(zhu)鐵(tie)心可改為三相(xiang)(xiang)三柱(zhu)鐵(tie)心，另一(yi)(yi)方面，美式(shi)箱(xiang)變(bian)的(de)高(gao)(gao)壓(ya)(ya)部分(fen)可以改型后從變(bian)壓(ya)(ya)器(qi)油 箱(xiang)內挪到(dao)油箱(xiang)外，占用(yong)(yong)高(gao)(gao)壓(ya)(ya)室空(kong)(kong)間。

　　美式(shi)箱(xiang)變體(ti)(ti)積(ji)比較小，布(bu)置(zhi)緊(jin)湊，高低(di)壓(ya)(ya)(ya)(ya)室(shi)(shi)(shi)(shi)內(nei)為開關(guan)，一股容(rong)量(liang)(liang)為800kVA以下;歐式(shi)箱(xiang)變體(ti)(ti)積(ji)大，南高壓(ya)(ya)(ya)(ya)室(shi)(shi)(shi)(shi)、變壓(ya)(ya)(ya)(ya)器和低(di)壓(ya)(ya)(ya)(ya)室(shi)(shi)(shi)(shi)組成，高低(di)壓(ya)(ya)(ya)(ya)室(shi)(shi)(shi)(shi)配(pei)置(zhi)開關(guan)柜，容(rong)量(liang)(liang)可(ke)以做(zuo)到(dao)20000kVA。

　　因此可以(yi)說同容(rong)量(liang)的兩(liang)種箱變相比(bi)較，美式(shi)(shi)箱變的結構更(geng)為合(he)理(li)。在住(zhu)宅(zhai)小區(qu)中，容(rong)量(liang)較小時(shi)選擇(ze)美式(shi)(shi)箱變，容(rong)量(liang)較大時(shi)選擇(ze)歐式(shi)(shi)箱變。

二、箱變布點方案探討

　　在傳統的(de)(de)城鎮(zhen)雙桿(gan)式公用變(bian)布(bu)置(zhi)中，由于住(zhu)戶(hu)(hu)用電容 量偏小，住(zhu)宅層數較低，一直采用小容量、多布(bu)點(dian)的(de)(de)原則。配變(bian)容量根據住(zhu)戶(hu)(hu)數而定，初裝容量一般100-250kVA，最(zui)終(zhong)容量400kVA以(yi)下(xia)。住(zhu)宅小區(qu)的(de)(de)箱變(bian)布(bu)置(zhi)是(shi)否也采用同樣的(de)(de)原則呢?經(jing)過認(ren)真分析，我們認(ren)為(wei)箱式小區(qu)變(bian)以(yi)規劃布(bu)點(dian)為(wei)主，以(yi)大容量為(wei)優化方案(an)，確(que)定最(zui)終(zhong)容量、一步(bu)到(dao)位。這是(shi)基于以(yi)下(xia)幾點(dian)考慮：

　　1、為美化環境、少(shao)占綠地

　　由于雙(shuang)(shuang)桿式配(pei)變(bian)臺區的(de)(de)(de)(de)10kV線路、低(di)壓(ya)線路是(shi)架空(kong)的(de)(de)(de)(de)，因此(ci)即(ji)便(bian)少放一臺配(pei) 變(bian)，由于電(dian)源必(bi)須供人(ren)每戶(hu)(hu)居民，其架空(kong)線路并不會減(jian)少，況且多(duo)(duo)放一臺配(pei)變(bian)也(ye)不占地(di)面綠(lv)地(di)，也(ye)就(jiu)是(shi)說，對(dui)于雙(shuang)(shuang)桿式配(pei)變(bian)臺區而言，臺區的(de)(de)(de)(de)多(duo)(duo)少對(dui)環(huan)境的(de)(de)(de)(de)總體影(ying)響基本不變(bian)，因此(ci)其比(bi)較適用多(duo)(duo)布點的(de)(de)(de)(de)原則。而對(dui)于箱(xiang)(xiang)(xiang)變(bian)而言，其進出線均為電(dian)纜，露出地(di)面的(de)(de)(de)(de)電(dian)力設備是(shi)箱(xiang)(xiang)(xiang)式變(bian)壓(ya)器，因此(ci)箱(xiang)(xiang)(xiang)變(bian)數(shu)(shu)量(liang)(liang)(liang)當然是(shi)越(yue)(yue)少越(yue)(yue)好。由于客戶(hu)(hu) 的(de)(de)(de)(de)供電(dian)容量(liang)(liang)(liang)是(shi)確(que)定的(de)(de)(de)(de)，因此(ci)，箱(xiang)(xiang)(xiang)變(bian)數(shu)(shu)量(liang)(liang)(liang)減(jian)少，就(jiu)意(yi)味著單臺箱(xiang)(xiang)(xiang)變(bian)的(de)(de)(de)(de)容量(liang)(liang)(liang)就(jiu)要增大(da)。

　　2、箱(xiang)變(bian)多少，對線(xian)損影響(xiang)不大

　　雙桿(gan)臺區小容量(liang)、多(duo)(duo)布點的(de)(de)(de)(de)一(yi)大(da)(da)優點是減(jian)(jian)(jian)少低壓(ya)線(xian)(xian)(xian)路(lu)的(de)(de)(de)(de)供(gong)電(dian)(dian)半(ban)徑(jing)、減(jian)(jian)(jian)少導(dao)線(xian)(xian)(xian)電(dian)(dian)流，從而(er)(er)達到減(jian)(jian)(jian)少低壓(ya)線(xian)(xian)(xian)路(lu)線(xian)(xian)(xian)損(sun)的(de)(de)(de)(de)目的(de)(de)(de)(de)。對于(yu)(yu)箱(xiang)(xiang)變(bian)，根據合理(li)布點的(de)(de)(de)(de)原則，其(qi)(qi)一(yi)般放置在(zai)二幢(chuang)(chuang)(chuang)或(huo)幾(ji)幢(chuang)(chuang)(chuang)房子的(de)(de)(de)(de)中間(jian)的(de)(de)(de)(de)綠地上(shang)，供(gong)電(dian)(dian)半(ban)徑(jing)不(bu)過幾(ji)十米，由(you)于(yu)(yu)可供(gong)布置的(de)(de)(de)(de)環境的(de)(de)(de)(de)限制(zhi)，供(gong)電(dian)(dian)半(ban)徑(jing)幾(ji)乎與(yu)箱(xiang)(xiang)變(bian)數(shu)量(liang)無關。每(mei)(mei)個箱(xiang)(xiang)變(bian)低壓(ya)出(chu)線(xian)(xian)(xian)3-6回，通過電(dian)(dian)纜排管供(gong)至每(mei)(mei)幢(chuang)(chuang)(chuang)樓(lou)旁的(de)(de)(de)(de)電(dian)(dian)纜分支(zhi)(zhi)箱(xiang)(xiang)，每(mei)(mei)個分支(zhi)(zhi)箱(xiang)(xiang)再出(chu)4-8回供(gong)電(dian)(dian)至每(mei)(mei)一(yi)梯戶(hu)的(de)(de)(de)(de)電(dian)(dian)能表箱(xiang)(xiang)處，每(mei)(mei)一(yi)電(dian)(dian)能表再供(gong)電(dian)(dian)至每(mei)(mei)一(yi)用戶(hu)。對于(yu)(yu)雙桿(gan)變(bian)而(er)(er)言(yan)，其(qi)(qi)低壓(ya)出(chu)線(xian)(xian)(xian)一(yi)般為(wei)左右二回 出(chu)線(xian)(xian)(xian)，因(yin)此，當線(xian)(xian)(xian)路(lu)上(shang)的(de)(de)(de)(de)用戶(hu)數(shu)增加(jia)(jia)時，其(qi)(qi)線(xian)(xian)(xian)路(lu)上(shang)流過的(de)(de)(de)(de)電(dian)(dian)流同時增大(da)(da)，而(er)(er)對于(yu)(yu)箱(xiang)(xiang)變(bian)而(er)(er)言(yan)，隨著(zhu)供(gong)電(dian)(dian)用戶(hu)數(shu)的(de)(de)(de)(de)增加(jia)(jia)，箱(xiang)(xiang)變(bian)出(chu)線(xian)(xian)(xian)回路(lu)數(shu)也同時增加(jia)(jia)，但每(mei)(mei)一(yi)回出(chu)線(xian)(xian)(xian)的(de)(de)(de)(de)供(gong)電(dian)(dian)負荷基本不(bu)變(bian)。所以，無論(lun)箱(xiang)(xiang)變(bian)數(shu)量(liang)多(duo)(duo)少，低壓(ya)線(xian)(xian)(xian)路(lu)的(de)(de)(de)(de)損(sun)耗基本保持不(bu)變(bian)。相反，由(you)于(yu)(yu)配變(bian)數(shu)量(liang)減(jian)(jian)(jian)少，在(zai)可比的(de)(de)(de)(de)情況(kuang)下，鐵損(sun)反而(er)(er)下降。

　　3、由小(xiao)區特點決定

　　在住宅小區箱變(bian)布點時，我(wo)們并非(fei)為了大容(rong)(rong)量而使用大變(bian)壓器，就如上述所言，采用合理布點的原則，即先確(que)定一個合理的供電范圍(wei)，再根據供電范圍(wei)內的用電負荷情(qing)況(kuang)計(ji)算配變(bian)容(rong)(rong)量，并根據此容(rong)(rong)量一步到位。

　　4、節約投資

　　一臺630kVA箱(xiang)變需資金約為(wei)21萬元(yuan)(yuan)，即(ji)333元(yuan)(yuan)/kVA：而一臺315kVA的(de)箱(xiang)變也需18萬元(yuan)(yuan)，即(ji)571元(yuan)(yuan)/kVA。這(zhe)是由于，箱(xiang)變內的(de)負(fu)荷開關等設備成本(ben)所(suo)占(zhan)比例較高，因此，單臺箱(xiang)變的(de)容(rong)量(liang)越大，其(qi)每一千伏(fu)安的(de)成本(ben)就越低。

　　5、可靠性分析

　　箱(xiang)變采(cai)用環網供(gong)電，可(ke)(ke)靠性較高，無論是使用二臺小容(rong)量(liang)的(de)(de)箱(xiang)變，還是采(cai)用一(yi)臺大容(rong)量(liang)的(de)(de)箱(xiang)變，其對用戶的(de)(de)供(gong)電可(ke)(ke)靠率基本一(yi)致。如低壓有特別重要的(de)(de)用戶，可(ke)(ke)通過電纜(lan)分(fen)支(zhi)箱(xiang)切換。

　　6、電壓分析

　　以S9型(xing)配(pei)(pei)(pei)(pei)(pei)變(bian)(bian)(bian)(bian)為例，100-500kVA配(pei)(pei)(pei)(pei)(pei)變(bian)(bian)(bian)(bian)的(de)(de)(de)(de)阻抗(kang)電(dian)(dian)(dian)壓(ya)(ya)均為4%，630-1600kVA配(pei)(pei)(pei)(pei)(pei)變(bian)(bian)(bian)(bian)的(de)(de)(de)(de)阻抗(kang)電(dian)(dian)(dian)壓(ya)(ya)也僅為4.5%。也就是說(shuo)，當(dang)小(xiao)容(rong)量(liang)的(de)(de)(de)(de)配(pei)(pei)(pei)(pei)(pei)變(bian)(bian)(bian)(bian)和(he)大 容(rong)量(liang)的(de)(de)(de)(de)配(pei)(pei)(pei)(pei)(pei)變(bian)(bian)(bian)(bian)均處于(yu)同等負(fu)荷(he)(he)率(lv)(lv)(lv)的(de)(de)(de)(de)情況下，其(qi)在(zai)配(pei)(pei)(pei)(pei)(pei)變(bian)(bian)(bian)(bian)上的(de)(de)(de)(de)電(dian)(dian)(dian)壓(ya)(ya)損失是一(yi)(yi)(yi)致的(de)(de)(de)(de)。事實(shi)上，如果采用(yong)(yong)二(er)臺(tai)(tai)(tai)250kVA配(pei)(pei)(pei)(pei)(pei)變(bian)(bian)(bian)(bian)替代一(yi)(yi)(yi)臺(tai)(tai)(tai)500kVA，由于(yu)500kVA所帶 用(yong)(yong)戶(hu)(hu)數是每(mei)臺(tai)(tai)(tai)250kVA配(pei)(pei)(pei)(pei)(pei)變(bian)(bian)(bian)(bian)所帶用(yong)(yong)戶(hu)(hu)數的(de)(de)(de)(de)一(yi)(yi)(yi)倍，因(yin)此(ci)，500kVA用(yong)(yong)戶(hu)(hu)用(yong)(yong)電(dian)(dian)(dian)的(de)(de)(de)(de)同時率(lv)(lv)(lv)要(yao)低(di)于(yu)250kVA用(yong)(yong)戶(hu)(hu)用(yong)(yong)電(dian)(dian)(dian)的(de)(de)(de)(de)同時率(lv)(lv)(lv)，即(ji)當(dang)出現(xian)更(geng)高(gao)負(fu)荷(he)(he)時，500kVA配(pei)(pei)(pei)(pei)(pei)變(bian)(bian)(bian)(bian)的(de)(de)(de)(de)負(fu)荷(he)(he)率(lv)(lv)(lv)要(yao)小(xiao)于(yu)每(mei)臺(tai)(tai)(tai)250kVA配(pei)(pei)(pei)(pei)(pei)變(bian)(bian)(bian)(bian)負(fu)荷(he)(he)率(lv)(lv)(lv)，因(yin)此(ci)，當(dang)出現(xian)更(geng)高(gao)負(fu)荷(he)(he)時，500kVA配(pei)(pei)(pei)(pei)(pei)變(bian)(bian)(bian)(bian)上的(de)(de)(de)(de)電(dian)(dian)(dian)壓(ya)(ya)損耗要(yao)比每(mei)臺(tai)(tai)(tai)250kVA配(pei)(pei)(pei)(pei)(pei)變(bian)(bian)(bian)(bian)都小(xiao)。 由于(yu)每(mei)回低(di)壓(ya)(ya)出線的(de)(de)(de)(de)負(fu)荷(he)(he)基本上都是一(yi)(yi)(yi)樣的(de)(de)(de)(de)，則電(dian)(dian)(dian)壓(ya)(ya)在(zai)低(di)壓(ya)(ya)線路上的(de)(de)(de)(de)損耗是一(yi)(yi)(yi)樣的(de)(de)(de)(de)，因(yin)此(ci)，采用(yong)(yong)大容(rong)量(liang)的(de)(de)(de)(de)箱變(bian)(bian)(bian)(bian)，其(qi)電(dian)(dian)(dian)壓(ya)(ya)要(yao)優(you)于(yu)小(xiao)容(rong)量(liang)配(pei)(pei)(pei)(pei)(pei)變(bian)(bian)(bian)(bian)。來(lai)源:輸配(pei)(pei)(pei)(pei)(pei)電(dian)(dian)(dian)設備網(wang)

三、箱式變電站容量的確定

　　容量的(de)確(que)(que)定應根據實際(ji)負(fu)荷的(de)大(da)小(xiao)(xiao)來確(que)(que)定，一(yi)般(ban)采用需要系(xi)(xi)數法(fa)進行計算。比如一(yi)，幢25層(ceng)一(yi)梯六戶(hu)的(de)高層(ceng)住宅，在戶(hu)外設置一(yi)臺箱變。每戶(hu)的(de)負(fu)荷按 7kW考慮，住宅小(xiao)(xiao)區內居民由于作息(xi)時間不同，同時系(xi)(xi)數小(xiao)(xiao)些(xie)。取同時系(xi)(xi)數一(yi)般(ban)為：50戶(hu)以(yi)下(xia)0.55，50～100戶(hu)0.45，100戶(hu)～200戶(hu) 0.40，200戶(hu)以(yi)上0.35。

　　此次供電每臺(tai)箱(xiang)變供電用戶(hu)150戶(hu)，據此，每臺(tai)配變的負(fu)荷(he)為7kW×150×0.33=346.5kW，以功率因數補償至(zhi)0.9計(ji)，則配變容(rong)量(liang)為385kVA，取整為400kVA。

四、使用中需注意的其他幾個問題

　　1、由于(yu)箱變是免維護設(she)計，在維護上不是很方便，因(yin)此在開關設(she)備的(de)(de)選(xuan)擇上我們應優先選(xuan)擇性(xing)能(neng)比較優良的(de)(de)，變壓器(qi)選(xuan)用(yong)性(xing)能(neng)好(hao)、低損型的(de)(de)，如現在推薦使用(yong)的(de)(de)卷鐵心S11型。

　　2、無論美式(shi)還是歐式(shi)箱變散(san)熱(re)都不是盡善盡美的(de)，尤(you)其是在太陽直曬比較嚴重的(de)地(di)區，溫度升高，影響塑殼斷(duan)(duan)路(lu)器分斷(duan)(duan)，使(shi)得(de)斷(duan)(duan)路(lu)器不能正常開(kai)斷(duan)(duan)負載(zai)及短路(lu)電流，易引發故(gu)障，因此散(san)熱(re)裝(zhuang)置是必要的(de)，尤(you)其要在箱式(shi)變基礎中做成散(san)熱(re)池，以增加(jia)對流。