描述
在10kV中性點(diǎn)不接地系統(tǒng)中,為了監(jiān)視系統(tǒng)中各相對地的絕緣狀況以及計(jì)量和保護(hù)的需要,在每個(gè)變電站的母線上均裝有電磁式電壓互感器。當(dāng)系統(tǒng)發(fā)生單相接地故障時(shí),將產(chǎn)生較高的諧振過電壓,影響系統(tǒng)設(shè)備的絕緣性能和使用壽命,進(jìn)而出現(xiàn)更頻繁的故障。
在中性點(diǎn)不接地系統(tǒng)中,當(dāng)其中一相出現(xiàn)金屬性接地時(shí),就會(huì)產(chǎn)生激磁涌流,導(dǎo)致電壓互感器鐵芯飽和。如A相接地,則Uan的電壓為零,非接地相Ubn、Ucn的電壓表指示為100V線電壓。電壓互感器開口三角兩端出現(xiàn)約100V電壓(正常時(shí)只有約3V),這個(gè)電壓將起動(dòng)絕緣檢查繼電器發(fā)出接地信號(hào)并報(bào)警。當(dāng)發(fā)生非金屬性短路接地時(shí),即高電阻、電弧、樹竹等單相接地。如A相發(fā)生接地,則Uan的電壓低于正常相電壓,Ubn、Ucn電壓則大于58V,且小于100V,電壓互感器開口三角處兩端有約70V電壓,達(dá)到絕緣檢查繼電器起動(dòng)值,發(fā)出接地信號(hào)并報(bào)警。電壓互感器二次側(cè)熔斷器熔斷或接觸不良時(shí),中央信號(hào)屏發(fā)出“電壓回路斷線”的預(yù)告信號(hào),同時(shí)光字牌亮,警鈴響。查電壓表可發(fā)現(xiàn):未熔斷相電壓表指示不變,熔斷相的電壓表指示降低或?yàn)榱恪S龅竭@種情況,可檢查電壓互感器二次回路接頭(端子排)處有無松動(dòng)、斷頭、電壓切換回路有無接觸不良等現(xiàn)象和電壓互感器二次熔斷器是否完好,找到松動(dòng)、斷線處應(yīng)立即處理;若更換熔斷器后再次熔斷,應(yīng)查明原因,不可隨意將其熔絲增大。?電壓互感器當(dāng)線路帶電設(shè)備上某點(diǎn)發(fā)生金屬接地時(shí),接地相電壓為零,而正常相的對地電壓值升高到原來的√3倍,產(chǎn)生嚴(yán)重的中性點(diǎn)位移。電壓互感器中性點(diǎn)位移電壓與接地相電壓大小相等,方向相反。如果把線路斷開后,接地仍未消除,則考慮是否與變電站內(nèi)設(shè)備有關(guān),如變壓器、電壓互感器、避雷器、斷路器等接地。
產(chǎn)品承諾:
保?證?全新原裝進(jìn)口,
保?證?安全準(zhǔn)時(shí)發(fā)貨,
保?證售后服務(wù)質(zhì)量,
優(yōu)勢價(jià)格,大量現(xiàn)貨。
主營DCS系統(tǒng)配件
機(jī)器人系統(tǒng)配件
大型伺服系統(tǒng)配件
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