正確選購單相電子式電能表 發揮電子式電能表的最優點

由于電(dian)(dian)(dian)子(zi)式電(dian)(dian)(dian)能表比感應(ying)式電(dian)(dian)(dian)能表準(zhun)確度(du)高、功耗低、起(qi)動電(dian)(dian)(dian)流小、負(fu)載范圍寬(kuan)、無機械磨(mo)損(sun)等諸多(duo)優(you)點，越來越廣泛地應(ying)用。但目前市場上電(dian)(dian)(dian)子(zi)式電(dian)(dian)(dian)能表廠家繁多(duo)，質(zhi)量參差不(bu)齊，選擇不(bu)好，不(bu)僅不(bu)能發揮電(dian)(dian)(dian)子(zi)式電(dian)(dian)(dian)能表的(de)優(you)點，反而會(hui)帶來不(bu)應(ying)有(you)的(de)損(sun)失和增加(jia)維護(hu)管理的(de)工作量。

電(dian)(dian)(dian)子(zi)式(shi)電(dian)(dian)(dian)能(neng)(neng)表(biao)(biao)(biao)與我(wo)們熟悉(xi)的(de)(de)感應式(shi)電(dian)(dian)(dian)能(neng)(neng)表(biao)(biao)(biao)(俗稱機(ji)械表(biao)(biao)(biao))，既有(you)相同(tong)(tong)的(de)(de)地(di)(di)方(fang)，也有(you)不(bu)相同(tong)(tong)的(de)(de)地(di)(di)方(fang)，且不(bu)同(tong)(tong)的(de)(de)地(di)(di)方(fang)更多，特別是表(biao)(biao)(biao)的(de)(de)內部(bu)，感應式(shi)電(dian)(dian)(dian)能(neng)(neng)表(biao)(biao)(biao)是采用電(dian)(dian)(dian)磁感應元(yuan)件(jian)，里面是鐵芯、鐵圈加機(ji)械傳動(dong)裝(zhuang)置；而電(dian)(dian)(dian)子(zi)式(shi)電(dian)(dian)(dian)能(neng)(neng)表(biao)(biao)(biao)則主要是采用電(dian)(dian)(dian)子(zi)元(yuan)件(jian)，即：電(dian)(dian)(dian)阻、電(dian)(dian)(dian)容加集成(cheng)電(dian)(dian)(dian)路等。因此，應根(gen)據電(dian)(dian)(dian)子(zi)式(shi)電(dian)(dian)(dian)能(neng)(neng)表(biao)(biao)(biao)的(de)(de)這一特性來進行選(xuan)擇。換(huan)句(ju)話(hua)說要以電(dian)(dian)(dian)子(zi)設備(bei)的(de)(de)技(ji)術(shu)(shu)要求(qiu)進行選(xuan)擇，而不(bu)能(neng)(neng)簡單的(de)(de)照(zhao)搬以前選(xuan)用機(ji)械式(shi)電(dian)(dian)(dian)能(neng)(neng)表(biao)(biao)(biao)的(de)(de)技(ji)術(shu)(shu)要求(qiu)選(xuan)擇電(dian)(dian)(dian)子(zi)式(shi)電(dian)(dian)(dian)能(neng)(neng)表(biao)(biao)(biao)(當然，也有(you)可以借鑒的(de)(de)地(di)(di)方(fang))。現(xian)就(jiu)我(wo)們在工作(zuo)中(zhong)體(ti)會，談(tan)談(tan)單相電(dian)(dian)(dian)子(zi)式(shi)電(dian)(dian)(dian)能(neng)(neng)表(biao)(biao)(biao)的(de)(de)選(xuan)購，供有(you)關的(de)(de)工作(zuo)人員參(can)考。

工具/原料

目測

電工測量儀器

必要的五金工具

步驟/方法

運行中的電能表質量抽查

電表在安裝運行(xing)一(yi)段時(shi)間(jian)(jian)后，必須進(jin)行(xing)抽查(cha)。抽查(cha)的(de)時(shi)間(jian)(jian)間(jian)(jian)隔和抽查(cha)比(bi)例(li)可以(yi)根(gen)據(ju)運行(xing)中電能表的(de)質(zhi)量(liang)情況(kuang)而定(ding)(ding)。同一(yi)廠(chang)家(jia)同一(yi)批次(ci)的(de)電能表，故障率(lv)小、誤差變(bian)化(hua)小、合格率(lv)高(gao)的(de)可以(yi)減少(shao)(shao)抽查(cha)比(bi)例(li)和抽查(cha)時(shi)間(jian)(jian)間(jian)(jian)隔。一(yi)般情況(kuang)下(xia)，首次(ci)選(xuan)用(yong)的(de)廠(chang)家(jia)產品半(ban)年(nian)(nian)內抽查(cha)率(lv)不能少(shao)(shao)于(yu)5%。一(yi)年(nian)(nian)內抽查(cha)比(bi)率(lv)不能少(shao)(shao)于(yu)10%。如果質(zhi)量(liang)穩定(ding)(ding)，誤差變(bian)化(hua)小，則可以(yi)減少(shao)(shao)抽查(cha)比(bi)例(li)，但(dan)每年(nian)(nian)至少(shao)(shao)要(yao)抽檢1%，以(yi)監(jian)測電能表質(zhi)量(liang)隨時(shi)間(jian)(jian)變(bian)化(hua)情況(kuang)。把電能表的(de)選(xuan)購從事(shi)前選(xuan)擇延伸到整(zheng)個(ge)使用(yong)過程之中，通過監(jian)控(kong)使用(yong)中的(de)情況(kuang)，進(jin)一(yi)步提(ti)高(gao)選(xuan)購水平。

查驗生產廠家所必須具備的基本技術條件

電能表是(shi)屬國家強制(zhi)檢驗(yan)計量(liang)器(qi)(qi)具(ju)，根據計量(liang)法規定，所選電能表必須具(ju)有省級(ji)以上(shang)技術監督(du)局頒(ban)發的(de)制(zhi)造(zao)計量(liang)器(qi)(qi)具(ju)許可(ke)(ke)證(zheng)(zheng)(zheng)(CMC證(zheng)(zheng)(zheng))。這是(shi)電能表生(sheng)產(chan)廠家所必須具(ju)備的(de)條(tiao)件(jian)(jian)和必須履行的(de)法律手(shou)續。它(ta)可(ke)(ke)以證(zheng)(zheng)(zheng)明(ming)廠家具(ju)備了(le)基本的(de)設施(shi)、人員和檢測儀器(qi)(qi)設備，是(shi)可(ke)(ke)以生(sheng)產(chan)銷售(shou)的(de)產(chan)品。但是(shi)在目(mu)(mu)前市場競爭激烈的(de)情況(kuang)下(xia)，供(gong)電企(qi)業(ye)有更大(da)的(de)選擇余地(di)，因此，還可(ke)(ke)以多比較一下(xia)其他證(zheng)(zheng)(zheng)明(ming)產(chan)品質量(liang)的(de)文件(jian)(jian)。如：權威(wei)部門的(de)鑒(jian)定報告、壽命(ming)試驗(yan)報告、被列入國家經貿委“全(quan)國城鄉電網建設與改造(zao)所需設備產(chan)品及生(sheng)產(chan)企(qi)業(ye)推薦(jian)目(mu)(mu)錄”、ISO9000質量(liang)認證(zheng)(zheng)(zheng)等等。這些(xie)都是(shi)證(zheng)(zheng)(zheng)明(ming)產(chan)品質量(liang)的(de)重要文件(jian)(jian)。

對電能表實物進行檢驗

對廠(chang)家送來(lai)的(de)電能表實物進行檢(jian)(jian)驗，主要是從以下幾個方(fang)(fang)面(mian)進行。即：機械要求(qiu)(qiu)、所能適應的(de)氣候(hou)條件(jian)、電氣要求(qiu)(qiu)、電磁兼容性、準(zhun)確度要求(qiu)(qiu)這五個方(fang)(fang)面(mian)。這五個方(fang)(fang)面(mian)在(zai)國家標準(zhun)《1級(ji)(ji)(ji)和2級(ji)(ji)(ji)靜(jing)止(zhi)式交流有(you)功電能表》(GB/T17215-1998)中(zhong)都有(you)明確的(de)規(gui)定(ding)。規(gui)定(ding)中(zhong)有(you)些(xie)試驗和檢(jian)(jian)驗項目一般地市級(ji)(ji)(ji)及縣級(ji)(ji)(ji)供電企業有(you)條件(jian)檢(jian)(jian)驗，但有(you)相當多的(de)項目還不(bu)具備條件(jian)檢(jian)(jian)驗。下面(mian)將(jiang)需要注意的(de)地方(fang)(fang)和解決的(de)辦(ban)法(fa)做一簡要說明。

(1)準確度要求：

準確(que)度要求包括，電(dian)(dian)(dian)流及(ji)功率因(yin)數(shu)改變(bian)、電(dian)(dian)(dian)壓(ya)改變(bian)、頻率改變(bian)、起動(dong)試(shi)驗(yan)、潛(qian)力試(shi)驗(yan)、走(zou)字試(shi)驗(yan)等這(zhe)些項(xiang)目的(de)(de)檢(jian)(jian)驗(yan)一(yi)般地(di)市(shi)級(ji)及(ji)縣級(ji)供電(dian)(dian)(dian)企業都能(neng)進(jin)行檢(jian)(jian)驗(yan)。電(dian)(dian)(dian)子式(shi)電(dian)(dian)(dian)能(neng)表(biao)在(zai)規(gui)程(cheng)規(gui)定(ding)的(de)(de)負載(zai)(zai)(zai)范(fan)(fan)圍(wei)內，一(yi)般線(xian)性度都比較(jiao)好，但(dan)不(bu)同廠家的(de)(de)表(biao)實際(ji)準確(que)計(ji)量(liang)的(de)(de)負載(zai)(zai)(zai)范(fan)(fan)圍(wei)有(you)(you)很大差(cha)別，由(you)于(yu)現(xian)場實際(ji)負載(zai)(zai)(zai)電(dian)(dian)(dian)流是(shi)經常變(bian)化的(de)(de)，能(neng)準確(que)計(ji)量(liang)的(de)(de)負載(zai)(zai)(zai)范(fan)(fan)圍(wei)越寬，表(biao)的(de)(de)負載(zai)(zai)(zai)性能(neng)越好。在(zai)農村有(you)(you)些地(di)區電(dian)(dian)(dian)網電(dian)(dian)(dian)壓(ya)波(bo)動(dong)比較(jiao)大。要注(zhu)意(yi)檢(jian)(jian)查(cha)(cha)電(dian)(dian)(dian)壓(ya)波(bo)動(dong)極限情況下(xia)，電(dian)(dian)(dian)能(neng)表(biao)的(de)(de)誤差(cha)。特別是(shi)低(di)電(dian)(dian)(dian)壓(ya)時的(de)(de)輕載(zai)(zai)(zai)誤差(cha)和電(dian)(dian)(dian)能(neng)表(biao)走(zou)字是(shi)否有(you)(you)力，檢(jian)(jian)查(cha)(cha)表(biao)內直流電(dian)(dian)(dian)源電(dian)(dian)(dian)壓(ya)不(bu)能(neng)下(xia)降(jiang)到計(ji)量(liang)器及(ji)芯片的(de)(de)工作電(dian)(dian)(dian)壓(ya)以(yi)下(xia)，直流電(dian)(dian)(dian)源的(de)(de)波(bo)紋不(bu)能(neng)有(you)(you)明顯地(di)增加，中儀電(dian)(dian)(dian)子生產的(de)(de)單相電(dian)(dian)(dian)子式(shi)電(dian)(dian)(dian)能(neng)表(biao)及(ji)三相電(dian)(dian)(dian)子式(shi)電(dian)(dian)(dian)能(neng)表(biao)質(zhi)保一(yi)年，讓您用的(de)(de)放心。

準確度要(yao)求還包括，如諧波、外部磁感應(ying)、高頻電磁場影響等。一般地市(shi)級及縣級供電企業不具(ju)備(bei)條(tiao)件檢(jian)驗(yan)(yan)，可以(yi)請省級電力試驗(yan)(yan)所(suo)檢(jian)驗(yan)(yan)。

(2)氣候條件和電磁兼容性能：

這(zhe)兩項對電(dian)(dian)(dian)子(zi)式電(dian)(dian)(dian)能(neng)(neng)來說都很(hen)重(zhong)要(yao)。尤其是電(dian)(dian)(dian)磁(ci)兼容性能(neng)(neng)對電(dian)(dian)(dian)子(zi)式電(dian)(dian)(dian)能(neng)(neng)表影響極為嚴重(zhong)，電(dian)(dian)(dian)磁(ci)兼容性能(neng)(neng)較差的(de)(de)表，現場運行(xing)中往往出現“死(si)機(ji)(ji)”、“飛字”等現象，甚至內(nei)部電(dian)(dian)(dian)子(zi)元件損(sun)壞。這(zhe)是電(dian)(dian)(dian)子(zi)式電(dian)(dian)(dian)能(neng)(neng)表有(you)(you)別于機(ji)(ji)械式電(dian)(dian)(dian)能(neng)(neng)表的(de)(de)一(yi)(yi)個(ge)重(zhong)要(yao)特性。電(dian)(dian)(dian)磁(ci)兼容檢(jian)驗(yan)(yan)一(yi)(yi)共(gong)有(you)(you)5個(ge)項目(mu)，即：靜電(dian)(dian)(dian)放電(dian)(dian)(dian)試(shi)(shi)驗(yan)(yan)、高頻(pin)電(dian)(dian)(dian)磁(ci)場試(shi)(shi)驗(yan)(yan)、電(dian)(dian)(dian)快速瞬變脈沖群試(shi)(shi)驗(yan)(yan)、浪(lang)涌試(shi)(shi)驗(yan)(yan)、無(wu)線電(dian)(dian)(dian)干擾抑制試(shi)(shi)驗(yan)(yan)。其中浪(lang)涌和脈沖群比較接近電(dian)(dian)(dian)網中的(de)(de)一(yi)(yi)些瞬態情況，建議有(you)(you)條件的(de)(de)地市級及(ji)縣(xian)級供(gong)電(dian)(dian)(dian)企業購(gou)置相(xiang)應(ying)設備，對電(dian)(dian)(dian)能(neng)(neng)表進行(xing)抽查檢(jian)驗(yan)(yan)。

(3)電氣要求：

電(dian)(dian)(dian)氣要(yao)求(qiu)的(de)功率(lv)消耗檢(jian)(jian)驗(yan)(yan)，包括電(dian)(dian)(dian)壓(ya)線路和電(dian)(dian)(dian)流(liu)線路，可(ke)以(yi)用互感器(qi)校(xiao)驗(yan)(yan)儀測量電(dian)(dian)(dian)能(neng)(neng)表的(de)電(dian)(dian)(dian)壓(ya)、電(dian)(dian)(dian)流(liu)和負(fu)載阻抗(kang)后(hou)，計算出(chu)額定(ding)電(dian)(dian)(dian)壓(ya)、額定(ding)電(dian)(dian)(dian)流(liu)下(xia)電(dian)(dian)(dian)能(neng)(neng)表的(de)功率(lv)消耗。這種方(fang)法既準(zhun)確又(you)方(fang)便；電(dian)(dian)(dian)源影(ying)響、電(dian)(dian)(dian)壓(ya)降(jiang)落和短(duan)時中(zhong)斷、自(zi)熱影(ying)響可(ke)以(yi)在電(dian)(dian)(dian)能(neng)(neng)表校(xiao)驗(yan)(yan)臺(tai)上模擬(ni)進行；短(duan)時過電(dian)(dian)(dian)流(liu)會影(ying)響檢(jian)(jian)驗(yan)(yan)，嚴格按規程定(ding)義做比較(jiao)困(kun)難，可(ke)以(yi)在2倍最大電(dian)(dian)(dian)流(liu)下(xia)，逐步延長時間，檢(jian)(jian)測電(dian)(dian)(dian)能(neng)(neng)表的(de)溫升(電(dian)(dian)(dian)流(liu)端子及取樣電(dian)(dian)(dian)阻)和誤(wu)差(cha)。這可(ke)以(yi)了(le)解電(dian)(dian)(dian)能(neng)(neng)表過負(fu)載后(hou)的(de)損壞程度。

為防止(zhi)低壓(ya)供電(dian)(dian)線路(lu)中性點斷(duan)開后，因負載不平衡(heng)引起某相(xiang)電(dian)(dian)壓(ya)升高燒壞(huai)電(dian)(dian)能(neng)表(biao)的(de)情況發生，將單相(xiang)電(dian)(dian)表(biao)的(de)輸(shu)入(ru)電(dian)(dian)壓(ya)升高到(dao)420V，經過4小時后，再在額定電(dian)(dian)壓(ya)下(xia)檢驗電(dian)(dian)能(neng)表(biao)應(ying)合格(試驗時要(yao)有人值守(shou)，注(zhu)意安全，發現(xian)有異常立即(ji)斷(duan)電(dian)(dian)檢查(cha))。

(4)機械要求：

機械(xie)要(yao)(yao)(yao)求(qiu)中的絕大部分內容是(shi)(shi)可以通過直觀檢查(cha)和(he)(he)(he)簡(jian)單的試驗方法進行(xing)檢驗的。如：四防(fang)(fang)(防(fang)(fang)電(dian)擊；防(fang)(fang)過高(gao)溫(wen)度；防(fang)(fang)火焰蔓(man)延；防(fang)(fang)固體異物、灰塵和(he)(he)(he)水(shui)進入)；鉛封方便可靠(只有(you)破壞鉛封后才能(neng)(neng)觸及(ji)儀表(biao)內部部件(jian))；接(jie)線端子(zi)應有(you)足夠的絕緣性能(neng)(neng)和(he)(he)(he)機械(xie)強度；表(biao)殼的結構和(he)(he)(he)裝配應能(neng)(neng)保證(zheng)在出(chu)現非(fei)永久性變(bian)形(xing)時(shi)不妨礙儀表(biao)正常工作；銘牌、接(jie)線圖(tu)、端子(zi)標(biao)志符合要(yao)(yao)(yao)求(qiu)等等。這(zhe)些要(yao)(yao)(yao)求(qiu)都是(shi)(shi)保證(zheng)電(dian)能(neng)(neng)表(biao)安(an)全運行(xing)的最基(ji)本要(yao)(yao)(yao)求(qiu)，是(shi)(shi)可以憑經驗觀察和(he)(he)(he)識別的。選(xuan)用(yong)(yong)決(jue)不能(neng)(neng)忽(hu)視(shi)。特別端子(zi)板要(yao)(yao)(yao)選(xuan)用(yong)(yong)阻燃材料(liao)，如選(xuan)用(yong)(yong)注(zhu)射(she)型酚醛樹脂；外殼采用(yong)(yong)ABS工程塑料(liao)時(shi)要(yao)(yao)(yao)注(zhu)意檢查(cha)是(shi)(shi)否(fou)阻燃；外殼不能(neng)(neng)有(you)明(ming)顯變(bian)形(xing)影響密封性能(neng)(neng)和(he)(he)(he)內部元件(jian)有(you)明(ming)顯的相對位移。

注意事項

另(ling)外(wai)需要(yao)注(zhu)意的(de)有(you)(you)，由于目前電(dian)(dian)子表的(de)機(ji)(ji)械計量(liang)器(qi)，還沒有(you)(you)從原(yuan)理上根本解決卡字問(wen)題。主要(yao)是(shi)通過選擇制造工藝(yi)好的(de)計量(liang)器(qi)和(he)進(jin)廠時嚴格篩選保(bao)證電(dian)(dian)能表整機(ji)(ji)質(zhi)(zhi)(zhi)量(liang)。因此，要(yao)特別(bie)注(zhu)意計量(liang)器(qi)的(de)質(zhi)(zhi)(zhi)量(liang)。步進(jin)電(dian)(dian)機(ji)(ji)有(you)(you)屏蔽可(ke)(ke)以(yi)防(fang)電(dian)(dian)磁(ci)干擾，外(wai)殼采(cai)用(yong)鋁合(he)金支架、齒輪精(jing)細(xi)、無毛(mao)刺、材料不易(yi)變形、有(you)(you)自(zi)潤滑性能、步進(jin)電(dian)(dian)機(ji)(ji)磁(ci)性能強、加工精(jing)密，都可(ke)(ke)以(yi)減少卡字的(de)問(wen)題。要(yao)注(zhu)意仔細(xi)檢查和(he)了解。再就(jiu)是(shi)要(yao)進(jin)行走(zou)字檢驗。為更嚴格地(di)(di)考核計量(liang)器(qi)質(zhi)(zhi)(zhi)量(liang)，保(bao)證安裝到現場的(de)電(dian)(dian)能表在電(dian)(dian)壓允許范圍內(nei)都能正(zheng)確(que)計量(liang)，建議采(cai)用(yong)本地(di)(di)區電(dian)(dian)網可(ke)(ke)能出現的(de)最低(di)(不考慮(lv)暫態)電(dian)(dian)壓進(jin)行走(zou)字試驗。