10 kV小電阻接地系統(tǒng)的參數(shù)特點(diǎn)及其短路計(jì)算

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摘　要：
介紹了10kV小電阻接地系統(tǒng)的特點(diǎn)，采用對(duì)稱分量法對(duì)單相接地故障進(jìn)行了序網(wǎng)分析，在給定的初始參數(shù)條件下，提出了小電阻接地系統(tǒng)參數(shù)的一些特點(diǎn)，并作了分析計(jì)算，得出單相接地故障時(shí)系統(tǒng)線電壓仍維持平衡的結(jié)論。最后對(duì)有關(guān)接地設(shè)備的選擇給出了計(jì)算方法。
關(guān)鍵詞：中性點(diǎn)小電阻接地；對(duì)稱分量法；短路計(jì)算

Parametric attributes of 10 kV power system grounded by small resistance and its short-circuit calculation
Abstract：The features of 10 kV distribution system grounded by small resistance are described in this paper.The sequential network analysis of single-phase earth fault is conducted using the symmetrical component method.Given initial parameters，some parametric attributes of such system are presented along with analytical computation.It draws a conclusion that the line voltage of the system remains balanced in spite of single-phase ground faults.The computing method for selecting relevant grounding apparatus is proposed at last.
Key words：neutral grounding by small resistance；symmetrical component method；short circuit calculation
　　中性點(diǎn)經(jīng)小電阻接地的配電系統(tǒng)在城市電網(wǎng)中已越來越廣泛地被采用。部分城市電網(wǎng)主要以電纜作為送電線路，且使用緊湊型的全封閉式的開關(guān)設(shè)備及氧化鋅避雷器，有些城市使用了不少耐壓標(biāo)準(zhǔn)較低的電纜。這樣的系統(tǒng)有幾個(gè)特點(diǎn)：a)系統(tǒng)電容電流較大，通常超過50 A，單相接地故障后會(huì)產(chǎn)生較高的內(nèi)部過電壓；b)單相接地故障概率比架空出線少得多；c)設(shè)備不允許在單相接地后約3倍的工頻過電壓下再連續(xù)運(yùn)行。這樣要求當(dāng)系統(tǒng)發(fā)生單相接地后應(yīng)立即切除故障線路，采用小電阻接地有利于繼電保護(hù)裝置可靠迅速地檢測并切除故障回路，小電阻接地還可改善系統(tǒng)參數(shù)減少接地故障時(shí)的內(nèi)部過電壓值。
　　小電阻接地系統(tǒng)的分析計(jì)算在有關(guān)手冊(cè)及參考書中均未做深入的研究，本文嘗試在這方面進(jìn)行一些分析探討。