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摘 要:污閃是電力系統(tǒng)安全運(yùn)行的嚴(yán)重威脅，提取污穢絕緣子泄漏電流特征量是有效實(shí)現(xiàn)污閃預(yù)警的前提之一，目前污閃預(yù)警并不十分理想的原因之一是表征污閃與泄漏電流關(guān)系的特征量尚未達(dá)成共識(shí)。以人工污穢試驗(yàn)為基礎(chǔ)，結(jié)合交流下污穢絕緣子表面電弧放電機(jī)制，分析了鹽密和濕度(relative humidity，RH)對(duì)絕緣子表面泄漏電流相位(θ )的影響，泄漏電流的總諧波畸變率(total harmonic distortion，THD)、高次諧波和低次諧波與泄漏電流波形畸變之間的內(nèi)在聯(lián)系。結(jié)果表明：θ 隨RH 的增加而減??；泄漏電流波形畸變的主要原因是電弧放電產(chǎn)生的3 次諧波，輕污時(shí)THD隨RH 的增加而緩慢增加，污穢較重時(shí)THD 隨RH 的增加呈先減小后增加的趨勢(shì)，存在極小值，在THD 極小值處，污穢絕緣子開始產(chǎn)生局部放電現(xiàn)象。根據(jù)理論分析和試驗(yàn)驗(yàn)證，提出可利用θ 和THD 的變化趨勢(shì)在空氣濕度較低時(shí)進(jìn)行污閃預(yù)警。 關(guān)鍵詞：泄漏電流 污穢絕緣子 相對(duì)濕度 相位 總諧波畸變率
ABSTRACT:The flashover of polluted insulators greatly threatens security of the power system. One of the preconditions for flashover prediction is to obtain the effective leakage current characteristics of polluted insulators, but there is still no consensus achieved on the relation between the flashover and leakage current characteristics, which is one of the reasons for imperfect flashover prediction system. Based on the AC flashover model, the phase (θ ) of leakage current has been studied under different relative humidity (RH) and salt deposit density (SDD) according to artificial pollution tests, and the relationships among the waveform distortion of leakage current, total harmonic distortion (THD), low frequency harmonic components and high frequency harmonic components were analyzed. It has been found that θ decreases with the increasing of RH. The main cause of the waveform distortion of leakage current is the third harmonic when arc discharge appears. The THD increases slowly with the increasing of RH under light contamination, while the THD decreases firstly then increases with the increasing of RH under moderate and heavy contamination; there is a minimum value to THD, and discharge appears on the surface of insulators when THD becomes the minimum value. Consequently, the THD and θ can be used to predict the flashover under low RH according to the theoretical analysis and test results. Keywords: leakage current；polluted insulator；relative humidity；phase；total harmonic distortion |
