缺乏(fa)電(dian)(dian)網實測(ce)數據來(lai)驗(yan)證電(dian)(dian)網運(yun)行(xing)新形態對(dui)(dui)繼電(dian)(dian)保護(hu)的(de)(de)(de)(de)影響。目前(qian),學術界已開(kai)展大量的(de)(de)(de)(de)新型(xing)電(dian)(dian)力系統仿(fang)真(zhen)研(yan)究,基于仿(fang)真(zhen)數據分析諧波、直(zhi)流(liu)偏磁等對(dui)(dui)繼電(dian)(dian)保護(hu)的(de)(de)(de)(de)影響。電(dian)(dian)網是高度復雜的(de)(de)(de)(de)實時運(yun)行(xing)系統,難(nan)以用(yong)仿(fang)真(zhen)模型(xing)對(dui)(dui)其(qi)精(jing)準刻畫,需要實測(ce)數量來(lai)驗(yan)證仿(fang)真(zhen)是否有效。由于缺乏(fa)有效采集實際數據的(de)(de)(de)(de)技術手段,超高壓(ya)換流(liu)站周邊(bian)的(de)(de)(de)(de)諧波潮流(liu)和直(zhi)流(liu)偏磁、軌道交通產生的(de)(de)(de)(de)雜散(san)電(dian)(dian)流(liu)、STATCOM裝置的故障穿(chuan)越電(dian)(dian)流(liu)、分布式能源(yuan)并網故障電(dian)(dian)流(liu)等電(dian)(dian)網運行新特性數(shu)據無法(fa)在變電(dian)(dian)站內實現集(ji)中準確采集(ji)。
缺乏(fa)在軌道(dao)交通(tong)雜(za)散電(dian)(dian)流(liu)、分布式能源(yuan)接入電(dian)(dian)網情形下(xia)對繼(ji)電(dian)(dian)保(bao)(bao)護(hu)(hu)(hu)動(dong)作行為影響的(de)定(ding)量分析。目前,軌道(dao)交通(tong)雜(za)散電(dian)(dian)流(liu)和分布式能源(yuan)規(gui)模還較小(xiao),對繼(ji)電(dian)(dian)保(bao)(bao)護(hu)(hu)(hu)的(de)影響可忽略。但隨(sui)著(zhu)地鐵(tie)建設加快(kuai)和虛(xu)擬電(dian)(dian)廠(chang)大規(gui)模推廣,若不(bu)分析清(qing)楚(chu)其對繼(ji)電(dian)(dian)保(bao)(bao)護(hu)(hu)(hu)產生(sheng)的(de)定(ding)量影響,無法保(bao)(bao)證繼(ji)電(dian)(dian)保(bao)(bao)護(hu)(hu)(hu)靈敏(min)性和快(kuai)速性的(de)要求。
缺乏(fa)能(neng)夠(gou)提(ti)升繼(ji)(ji)電(dian)保護(hu)隱患主動預警水(shui)平(ping)的(de)智(zhi)能(neng)化(hua)繼(ji)(ji)電(dian)保護(hu)技術(shu)。目前(qian),繼(ji)(ji)電(dian)保護(hu)裝置(zhi)(zhi)及(ji)主子(zi)站系統數字化(hua)水(shui)平(ping)已有較大提(ti)升,可(ke)以做到運(yun)(yun)維人員發現已出現的(de)繼(ji)(ji)電(dian)保護(hu)裝置(zhi)(zhi)缺陷(xian),即能(neng)滿足(zu)事中處(chu)置(zhi)(zhi)的(de)要求。但在電(dian)網彈(dan)性降(jiang)低的(de)形勢下,我們(men)更(geng)需要繼(ji)(ji)電(dian)保護(hu)具備隱患預測(ce)能(neng)力(li),運(yun)(yun)維人員可(ke)以提(ti)前(qian)發現繼(ji)(ji)電(dian)保護(hu)裝置(zhi)(zhi)缺陷(xian)并及(ji)時處(chu)置(zhi)(zhi),防止電(dian)網故障和繼(ji)(ji)電(dian)保護(hu)裝置(zhi)(zhi)異常同時發生(sheng)導致的(de)大面積停電(dian)事件(jian)。
WBST-300電纜(lan)識(shi)別儀是用于(yu)將(jiang)某(mou)一特定電纜(lan)從一束(shu)電纜(lan)中識(shi)別出來(lai)的專用儀器(qi)。它(ta)是一小型化手提式,緊湊型儀器(qi),裝在鋁合金箱內,由一個信號(hao)發(fa)生器(qi),一個帶傳感器(qi)的接(jie)收機及連線構成。
一(yi)、工作(zuo)原理簡介(WBST-300帶電(dian)電(dian)纜識(shi)別機數(shu)據穩定可靠)
為了可靠準確地識(shi)別電纜,需要給被識(shi)別電纜加一(yi)特(te)殊(shu)的信號,該信號要被專用接(jie)收機(ji)接(jie)收,利用這一(yi)特(te)性便能識(shi)別出要找的電纜。
該儀器(qi)按(an)下(xia)述(shu)原理工作(zuo):
發生器將周期性(xing)的(de)單極性(xing)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)壓脈沖饋(kui)入要(yao)識別的(de)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)纜(lan)中(zhong),該(gai)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)纜(lan)需(xu)要(yao)在遠(yuan)端接(jie)地,以保證有(you)足夠大的(de)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)流(liu)(liu)(liu)(liu)流(liu)(liu)(liu)(liu)過(guo)(guo)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)纜(lan)。該(gai)系統要(yao)設計成返回(hui)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)流(liu)(liu)(liu)(liu)不要(yao)從(cong)同一(yi)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)纜(lan)中(zhong)返回(hui),能做(zuo)到這(zhe)一(yi)點,饋(kui)入電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)纜(lan)中(zhong)的(de)脈沖電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)流(liu)(liu)(liu)(liu)的(de)方(fang)向可做(zuo)為一(yi)明顯的(de)識別標(biao)準,流(liu)(liu)(liu)(liu)出(chu)去的(de)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)流(liu)(liu)(liu)(liu)僅從(cong)這(zhe)一(yi)根(gen)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)纜(lan)通過(guo)(guo),所有(you)其它(ta)鄰近電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)纜(lan)中(zhong)流(liu)(liu)(liu)(liu)過(guo)(guo)的(de)都是返回(hui)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)流(liu)(liu)(liu)(liu),但(dan)它(ta)們(men)的(de)極性(xing)相反。除了電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)流(liu)(liu)(liu)(liu)方(fang)向這(zhe)一(yi)實際(ji)差異外,電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)流(liu)(liu)(liu)(liu)幅度也是一(yi)識別特征(zheng),流(liu)(liu)(liu)(liu)出(chu)去的(de)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)流(liu)(liu)(liu)(liu)僅通過(guo)(guo)一(yi)根(gen)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)纜(lan)、而返回(hui)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)流(liu)(liu)(liu)(liu)可通過(guo)(guo)幾根(gen)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)纜(lan)、這(zhe)意味著流(liu)(liu)(liu)(liu)出(chu)去的(de)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)流(liu)(liu)(liu)(liu)比(bi)流(liu)(liu)(liu)(liu)過(guo)(guo)其它(ta)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)纜(lan)的(de)返回(hui)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)流(liu)(liu)(liu)(liu)大。
接(jie)(jie)收機的任務是探測(ce)流(liu)過電(dian)(dian)(dian)(dian)纜(lan)(lan)電(dian)(dian)(dian)(dian)流(liu)方(fang)向以及它的大(da)(da)小。為(wei)(wei)達到這一目(mu)的,電(dian)(dian)(dian)(dian)流(liu)傳(chuan)(chuan)(chuan)(chuan)感(gan)器(qi)(qi)(qi)被用作傳(chuan)(chuan)(chuan)(chuan)感(gan)器(qi)(qi)(qi),它帶有一放大(da)(da)器(qi)(qi)(qi)并串聯在電(dian)(dian)(dian)(dian)路中(zhong),傳(chuan)(chuan)(chuan)(chuan)感(gan)器(qi)(qi)(qi)鉗住被測(ce)電(dian)(dian)(dian)(dian)纜(lan)(lan),電(dian)(dian)(dian)(dian)流(liu)流(liu)過電(dian)(dian)(dian)(dian)纜(lan)(lan)產生(sheng)的磁場在傳(chuan)(chuan)(chuan)(chuan)感(gan)器(qi)(qi)(qi)的線圈中(zhong)感(gan)應出(chu)電(dian)(dian)(dian)(dian)壓(ya),該(gai)電(dian)(dian)(dian)(dian)壓(ya)極(ji)性由電(dian)(dian)(dian)(dian)流(liu)方(fang)向和傳(chuan)(chuan)(chuan)(chuan)感(gan)器(qi)(qi)(qi)線圈的方(fang)向決定。為(wei)(wei)了得到明顯有電(dian)(dian)(dian)(dian)流(liu)方(fang)向的電(dian)(dian)(dian)(dian)壓(ya)極(ji)性,對(dui)一束電(dian)(dian)(dian)(dian)纜(lan)(lan)中(zhong)所(suo)有電(dian)(dian)(dian)(dian)纜(lan)(lan)進(jin)行測(ce)試都采取(qu)相同正確的方(fang)向。傳(chuan)(chuan)(chuan)(chuan)感(gan)器(qi)(qi)(qi)線圈中(zhong)感(gan)應的電(dian)(dian)(dian)(dian)壓(ya)在表頭(tou)中(zhong)顯示出(chu)來(lai),如果(guo)傳(chuan)(chuan)(chuan)(chuan)感(gan)器(qi)(qi)(qi)按(an)上述(shu)方(fang)式連接(jie)(jie),指針擺動方(fang)向可顯示電(dian)(dian)(dian)(dian)流(liu)方(fang)向,即只(zhi)有電(dian)(dian)(dian)(dian)流(liu)流(liu)出(chu)的這根電(dian)(dian)(dian)(dian)纜(lan)(lan)指針向一邊偏,這根就是要(yao)找的電(dian)(dian)(dian)(dian)纜(lan)(lan)。所(suo)有其它電(dian)(dian)(dian)(dian)纜(lan)(lan)只(zhi)流(liu)過返回電(dian)(dian)(dian)(dian)流(liu),指針向另一邊偏、或無脈(mo)動電(dian)(dian)(dian)(dian)流(liu),指針不偏轉。接(jie)(jie)收機上的放大(da)(da)調(diao)節器(qi)(qi)(qi)可調(diao)整信(xin)號強(qiang)度(du)。
二(er)、外型及功能介紹(WBST-300帶電(dian)電(dian)纜(lan)識別(bie)機數據(ju)穩定可靠)
識別儀主機(ji)及(ji)接(jie)收機(ji)外型如圖(tu)1所(suo)示
主機外型尺寸: 370mm×270mm×210mm
接收機外型尺寸(cun):170mm×60mm×140mm
識別儀主機各部分功能如下:
1. 電(dian)(dian)源開關:控制整(zheng)機電(dian)(dian)源通斷。
2. 電源輸(shu)入插座:用儀器(qi)所配專用電源線(xian),輸(shu)入50HZ、220V交(jiao)流電源。儀器使用時,應獨(du)立(li)使用三孔電源插座(zuo),插座(zuo)接(jie)地線就近(jin)直接(jie)接(jie)地。
3. 保險座:儀器使用10A保(bao)險(xian)芯,損(sun)壞時(shi)應換(huan)同(tong)規格保(bao)險(xian)芯。
4. 黑接線(xian)(xian)柱(zhu):測(ce)試時,用配套黑色(se)測(ce)試線(xian)(xian)(Ф11插(cha)頭)插(cha)入此插(cha)孔,另一端測試夾接(jie)系(xi)統地。
5. 紅接線(xian)柱:測試時,用(yong)配套紅色測試線(xian)(Ф11插頭)插入此插孔,另一端測(ce)試(shi)夾接被(bei)測(ce)電纜芯線。
6. 表頭(tou):指示輸出(chu)電流(liu)大小。
7. 輸(shu)出(chu)(chu)調節(jie):用(yong)于(yu)調整主機電流(liu)大(da)小,使(shi)用(yong)時根據測試電纜長短及接收器指示大(da)小適當調節(jie)。順(shun)時針旋轉輸(shu)出(chu)(chu)電流(liu)增大(da)。
接收機各(ge)部分功(gong)能如下:
電(dian)源開關:接(jie)收機電(dian)源接(jie)通與關斷。
幅(fu)度調節:順時針(zhen)旋轉,接(jie)收機電表指(zhi)示值(zhi)(zhi)增大(da),逆時針(zhen)旋轉,指(zhi)示值(zhi)(zhi)變小。
表頭(tou):指示輸入信號幅度大小與極性(xing)。
電(dian)源指(zhi)示(shi)燈:電(dian)源開關接(jie)通(tong)時,指(zhi)示(shi)燈亮。
三、工作方法(WBST-300帶電電纜識別機數據穩定可靠(kao))
電(dian)纜(lan)識別(bie)儀(yi)信號(hao)發(fa)生器(qi)由交(jiao)流(liu)(liu)(liu)電(dian)源供電(dian),它(ta)對已(yi)斷電(dian)的、要識別(bie)的電(dian)纜(lan)加(jia)上固(gu)定周期單極性的直流(liu)(liu)(liu)脈沖。發(fa)生器(qi)輸出(chu)線(xian)(xian)連在(zai)電(dian)纜(lan)芯(xin)線(xian)(xian)和接地點或地釘上,該電(dian)纜(lan)線(xian)(xian)鎧裝(zhuang)與大地斷開(kai),芯(xin)線(xian)(xian)在(zai)遠端(duan)與接地點或地釘相(xiang)連,該回路可傳(chuan)導脈沖電(dian)流(liu)(liu)(liu),它(ta)可由識別(bie)儀(yi)(yi)上的表頭讀出,電流(liu)大小由(you)環路電阻(zu)決定,環路電阻(zu)應(ying)盡可能小。識別儀(yi)(yi)接線圖如圖2所示
發射機與接收機開始(shi)正常工(gong)作后,傳感器線圈中(zhong)感應的電壓(ya)在接收機表(biao)頭(tou)中(zhong)顯示出(chu)來,表(biao)頭(tou)指針擺動方(fang)向可顯示電流(liu)方(fang)向,即只(zhi)有電流(liu)流(liu)出(chu)的這(zhe)根電纜(lan)(lan)(lan)指針向右偏并(bing)且(qie)擺幅(fu)較大,這(zhe)根就是要(yao)找(zhao)的電纜(lan)(lan)(lan)。所有其它電纜(lan)(lan)(lan)只(zhi)流(liu)過返(fan)回(hui)電流(liu),指針向左(zuo)偏并(bing)且(qie)擺幅(fu)極(ji)小。接收機上的輸出(chu)調(diao)節旋鈕可調(diao)整(zheng)信(xin)號強度。
1、儀器供(gong)電
電(dian)纜識別儀(yi)主機由(you)交(jiao)流220V供電(dian),接(jie)收機由一節9V電池(chi)(chi)供電、電池(chi)(chi)裝在接收機手(shou)把后(hou)(hou)蓋(gai)內。擰開(kai)后(hou)(hou)蓋(gai)兩(liang)側螺絲、拉(la)出后(hou)(hou)蓋(gai),可(ke)更(geng)換電池(chi)(chi)。
2、傳(chuan)感器
傳感器是一電流變換(huan)器,鉗口內部尺寸為120mm。當(dang)電流(liu)(liu)流(liu)(liu)過測試電纜,在傳感器內感應(ying)出(chu)電壓(ya),電壓(ya)幅度由(you)(you)電流(liu)(liu)強度決(jue)定(ding),其極性由(you)(you)電流(liu)(liu)方(fang)向決(jue)定(ding)。
3、可靠測試
一(yi)定要進行以下可靠測試,以避免造人(ren)員傷亡或損壞電(dian)(dian)纜識(shi)別儀及(ji)其(qi)它設備。使用電(dian)(dian)纜識(shi)別儀時,要對(dui)被測電(dian)(dian)纜進行帶電(dian)(dian)檢查,并確(que)保該電(dian)(dian)纜處于無電(dian)(dian)狀(zhuang)態。
將儀器接(jie)入(ru)被(bei)測(ce)電(dian)(dian)纜前,要對其附近末加保護(hu)的(de)儀器或(huo)電(dian)(dian)纜進行保障檢查,并將這些帶(dai)電(dian)(dian)部分用絕緣材料(liao)進行可靠保護(hu)。
四、準(zhun)備測(ce)試(WBST-300帶電(dian)電(dian)纜識別(bie)機數據穩定可靠)
1、主機準備
連接:
(1)在進行測(ce)試工作之前(qian),將被測(ce)電纜斷電,其周圍環境應(ying)處于可靠(kao)狀態。
(2)發生器與(yu)被(bei)測電纜相連(lian),紅色夾子(zi)與(yu)被(bei)識別(bie)電纜的(de)一(yi)根芯(xin)線或幾(ji)根芯(xin)線連(lian)到一(yi)起(qi)。將黑色夾子(zi)與(yu)地(di)釘相連(lian)。
(3)將電纜(lan)遠端的芯線與地(di)釘相連。
(4)將(jiang)電纜(lan)兩(liang)端的鎧(kai)裝與地線斷開。
(5)將電源(yuan)(yuan)線插(cha)(cha)入電源(yuan)(yuan)插(cha)(cha)座。
開機:
(1)逆時針方向調節輸出旋鈕到(dao)零。
(2)打開主機電源開關,對主機供電。
(3)緩慢調節輸出(chu)(chu)旋鈕,主機開始間斷向(xiang)電纜發(fa)出(chu)(chu)脈動直(zhi)流信(xin)號,使輸出(chu)(chu)脈動電流信(xin)號為(wei)5-15A之(zhi)間即可。
2、接收機(ji)準備
(1)從(cong)接(jie)收機手把背面卸下螺釘,將一節(jie)9V電池裝入(ru)接收(shou)機中,就可(ke)正常工作。
(2)接通(tong)接收機(ji)電源,紅色發光二極管(guan)亮(liang)。
(3)緩慢調節(jie)靈敏度旋鈕,使電表開始指示(shi)。
注意(yi)傳感器插入電纜的方向(xiang)及(ji)接(jie)收機(ji)表(biao)頭擺動幅(fu)度的
大小。
五(wu)、測試(WBST-300帶(dai)電(dian)電(dian)纜識別機數據(ju)穩(wen)定可(ke)靠)
1.設置(zhi)測試回路(lu)
為保(bao)證(zheng)儀器(qi)的正常(chang)使用(yong),應注意(yi)設置(zhi)測試回路。
將(jiang)(jiang)紅色(se)輸出(chu)插(cha)孔(kong)與(yu)要識別的電(dian)纜(lan)的芯(xin)線相連(lian),將(jiang)(jiang)黑色(se)輸出(chu)插(cha)孔(kong)與(yu)地(di)相連(lian),將(jiang)(jiang)電(dian)纜(lan)芯(xin)線在(zai)遠端(duan)與(yu)地(di)相連(lian)。如圖3所示
輸出電流在電纜線中(zhong)沿(yan)箭頭方向流向遠端(duan),通過大地返回發生(sheng)器,將被識別電纜的所有芯線連到(dao)一起,能得(de)到(dao)較清(qing)楚(chu)的信(xin)號。
2.儀器(qi)校(xiao)準
校準接收機(ji)時,要在(zai)始端處用傳感(gan)器卡(ka)住電纜(接近(jin)發生器),然后從0開始調整接(jie)收機的輸出幅度(du),直到(dao)表頭顯(xian)示(shi)讀數為4-6格,如果接收機過(guo)載,儀(yi)表指示過(guo)大(da),此時應減(jian)小輸(shu)出幅(fu)度。然后在(zai)需(xu)要檢測處用相(xiang)同(tong)的(de)接收靈敏(min)度進行檢測,用傳(chuan)感(gan)
器將每一(yi)(yi)根電(dian)纜(lan)(lan)都卡一(yi)(yi)遍,當卡住需(xu)要識別的電(dian)纜(lan)(lan)時,接(jie)收機表頭(tou)顯示讀數為4-6格,且向同一(yi)方(fang)向偏擺。
所有其它電(dian)纜(lan)要么(me)沒有讀(du)數,要么(me)讀(du)數極小且(qie)電(dian)流方向相反,即(ji)向另一方向偏擺。
3.測試實例(li)
實例1
由(you)于電(dian)(dian)(dian)纜(lan)屏蔽層通常與地相連,如(ru)果電(dian)(dian)(dian)纜(lan)束中(zhong),其它電(dian)(dian)(dian)纜(lan)也接到(dao)公共地上,發生(sheng)器(qi)上黑色輸(shu)出插孔(kong)可(ke)連到(dao)公共地上,返(fan)回電(dian)(dian)(dian)流在幾(ji)根電(dian)(dian)(dian)纜(lan)屏蔽層進行(xing)分配,將(jiang)返(fan)回電(dian)(dian)(dian)流分成許(xu)多支流,意味著被識別電(dian)(dian)(dian)纜(lan)的(de)差值電(dian)(dian)(dian)流較大,有用信(xin)號較清楚, “差值”的(de)意思是輸(shu)出電(dian)(dian)(dian)流和其分得(de)的(de)返(fan)回電(dian)(dian)(dian)流在同一通道內。如(ru)圖4所示(shi),圖(tu)4中有5根電纜,4號電纜(lan)是(shi)我們需(xu)要識(shi)(shi)別的(de),要識(shi)(shi)別的(de)電纜(lan)中“輸出電流”為20A。假設返回電流(liu)在(zai)(zai)所有電纜的屏蔽層(ceng)中平均分配,在(zai)(zai)要(yao)測的電纜中應有4A的(de)返回電(dian)(dian)流,要識別(bie)的(de)電(dian)(dian)纜中的(de)差值為:20A(輸出)-4A(返回)=16A(差值)
實(shi)例2
如果被測(ce)電(dian)纜的屏蔽(bi)(bi)層從系(xi)統地(di)中斷開(kai),其差值(zhi)將會(hui)得到改進,在該電(dian)纜的屏蔽(bi)(bi)層中,沒有(you)返回電(dian)流。如圖5所示
圖(tu)5中有5根電纜,4號電纜(lan)是我們需要的電纜(lan),要識別(bie)的電纜(lan)中“輸(shu)出電流”為20A。由(you)于(yu)電(dian)纜屏蔽層與地斷(duan)開,在(zai)其余(yu)4根電纜(lan)中分得的返(fan)回電流(liu)為:20A/4=5A,要識別電纜的電流差值為:20A-0=20A
實(shi)例3
用(yong)作返回(hui)電路的(de)(de)屏蔽層數量越少,從差值法中得到的(de)(de)讀數越小,極(ji)限情況是僅有兩根電纜(lan)的(de)(de)情況。如圖6所示
在(zai)圖(tu)6中有兩(liang)根(gen)電纜(lan),1號(hao)電(dian)(dian)纜(lan)是(shi)要識別的(de)電(dian)(dian)纜(lan),要識別的(de)電(dian)(dian)纜(lan)中輸出電(dian)(dian)流為20A,返(fan)回電流(liu)在兩根電纜的屏蔽層(ceng)中分配,因此每根電纜的屏蔽層(ceng)的返(fan)回電流(liu)為(wei)10A,產生的電流差為:20A-10A=10A
將電(dian)纜屏蔽(bi)層從公共地(di)上斷開,改善發生器的接地(di)狀況,在(zai)電(dian)纜遠端(duan)加一(yi)地(di)釘,差值電(dian)流會得到改善。如圖(tu)7所示
圖(tu)7中(zhong)有兩根電纜,1號電(dian)(dian)纜(lan)是(shi)要(yao)識(shi)別的電(dian)(dian)纜(lan),要(yao)識(shi)別的電(dian)(dian)纜(lan)中輸(shu)出電(dian)(dian)流為20A,返回(hui)電流在(zai)2號電纜屏(ping)蔽層中(zhong)為10A,產生的 值電流為:20A-0A=20A
實例4
如果沒有屏蔽層來(lai)構(gou)成(cheng)返回(hui)電(dian)路,返回(hui)電(dian)路可通(tong)過(guo)地釘(ding)(ding)來(lai)實(shi)現,此時(shi)需要兩個(ge)地釘(ding)(ding),一個(ge)地釘(ding)(ding)在電(dian)流遠端與電(dian)纜芯線相相連(lian),另外一個(ge)與主(zhu)機黑色輸出(chu)插孔相連(lian),如圖(tu)8所示
圖8中有(you)兩根(gen)電纜,1號電(dian)纜是我們要(yao)識(shi)別的電(dian)纜,要(yao)識(shi)別電(dian)纜的輸(shu)出電(dian)流為20A,返回電流通過地釘經大地回到發(fa)生器。
為保證(zheng)環路電(dian)阻的(de)阻抗盡可(ke)能低,地(di)釘與地(di)之(zhi)間要保證(zheng)接(jie)觸(chu)良好(將地(di)釘附近(jin)的(de)地(di)方弄濕(shi))。
警告:為確(que)保人身(shen)保障,對已(yi)(yi)確(que)定的電纜結果(guo),不能作為開據前的依據,已(yi)(yi)識別的電纜只能作為標示(shi)或掛牌(pai)的依據,如果(guo)要(yao)維修開鋸前,一(yi)定要(yao)進行扎釘(ding)試驗。
研究基于智能錄波(bo)器(qi)的(de)電(dian)網新特(te)性集中(zhong)監測技(ji)術(shu)(shu)(shu)和邊緣計(ji)算技(ji)術(shu)(shu)(shu),突破寬頻監測、自(zi)適(shi)應啟動、多事(shi)件(jian)聯動分(fen)析等技(ji)術(shu)(shu)(shu)難點(dian),實現(xian)各項電(dian)網運(yun)行新特(te)性實時采(cai)集和分(fen)析。
研究軌道(dao)交(jiao)通雜散(san)電(dian)流和(he)分(fen)布(bu)式能源對(dui)繼電(dian)保(bao)(bao)護的(de)影響(xiang),突(tu)破(po)雜散(san)電(dian)流諧(xie)波源建模、雜散(san)電(dian)流分(fen)布(bu)和(he)隔直裝(zhuang)置(zhi)交(jiao)互影響(xiang)、分(fen)布(bu)式電(dian)源的(de)整(zheng)定(ding)計(ji)算(suan)模型和(he)含(han)分(fen)布(bu)式電(dian)源的(de)電(dian)網整(zheng)定(ding)計(ji)算(suan)方法等技(ji)術難點,實現對(dui)繼電(dian)保(bao)(bao)護動作行為的(de)定(ding)量影響(xiang)分(fen)析(xi)。
研究繼電保護(hu)數字孿生技(ji)(ji)術,突(tu)破二次系統多(duo)維建模、自動(dong)成圖(tu)、小微傳感器集成、基于概率圖(tu)模型的預測算(suan)法等(deng)技(ji)(ji)術難點,實現繼電保護(hu)裝置隱患提(ti)前預警。
目前,深圳供電(dian)局(ju)在以上研究方面已取(qu)得初步成(cheng)效。例如,500kV鵬城站實現諧(xie)波潮流、STATCOM故障穿越電流(liu)(liu)監(jian)視實(shi)時集(ji)中監(jian)測;基于(yu)深圳(zhen)電網實(shi)際模型,完成地(di)鐵雜(za)散電流(liu)(liu)對距離(li)保(bao)護的定量(liang)分(fen)析研究,完成含分(fen)布式電源的110kV高壓(ya)電(dian)網中性點接地方案研究;提(ti)出國內頭一(yi)個雙向(xiang)互動的(de)數字孿生(sheng)二次系統示(shi)范(fan)站建設方案。后續,深圳(zhen)電(dian)網將持續推進繼電(dian)保(bao)護新技術研究,為大(da)型城市電(dian)網新型電(dian)力系統建設提(ti)供樣本(ben)。
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