直流电压下矿物油和天然酯中纤维颗粒运动及成桥特性的差异

Different Motion and Bridging Characteristics of Fiber Particles in Mineral Oil and Natural Ester Under DC Voltage

纤维颗粒是运行变压器中绝缘油品质的首要污染者,以矿物油和天然酯为研究对象,在相同直流电场作用下,对不同板-板电极距离下油中纤维颗粒的运动及成桥特性进行了对比分析。研究结果表明：当直流电场相同时,与天然酯相比,矿物油中纤维颗粒运动更快,更容易形成完整的＂纤维颗粒桥＂;矿物油中的＂纤维颗粒桥＂呈现与电场线方向平行的细圆柱状,而天然酯中＂纤维颗粒桥＂呈现三角锥形;随着板-板电极距离的增大,矿物油中形成最初＂浅桥＂所需的时间增大,＂纤维颗粒桥＂的密度减小,而天然酯则相反。颗粒的存在增大了绝缘油的泄漏电流,但2种油泄漏电流的变化趋势受电极距离的影响不同,天然酯的泄漏电流不易受颗粒影响。自直流加压至撤去电压后,2种绝缘油中的＂纤维颗粒桥＂均呈现动态变化的4个阶段：颗粒急剧运动阶段、完整＂纤维颗粒桥＂逐渐形成阶段、＂纤维颗粒桥＂密度逐渐增大阶段、＂纤维颗粒桥＂消散阶段。此外,研究发现＂纤维颗粒桥＂加压时的形成及撤去电压后的消散与电流陡增及陡降存在密切关系。

1 Fiber particles are the major pollutant deteriorating quality of transformer oil. For plate-plate electrodes with different distances, this paper studied different motion and bridging characteristics of fiber particles in mineral oil and natural ester under the same electrical field strength. The results indicate that fiber particles in mineral oil move faster, form complete bridges more easily than in the case of natural ester. The fiber bridges seem to be cylinders parallel to electric field lines, but the bridges in natural ester look like triangular cones. With increase of distance between plate electrodes, the time required for formation of initial ＂shallow bridge＂ in mineral oil increases and density of the fiber bridge decreases, contrary to the case with natural ester. Fiber particles in mineral oil cause increase of leakage current, but effect of electrode distances on the trend of leakage current in mineral oil and natural ester contaminated with fiber particles is different. Moreover, fiber particles have little impact on the leakage current in natural ester. From DC voltage application till to its removal, the fiber bridges in insulating oil present 4 dynamically changing stages： stage of particle rapid movement, stage of gradually forming complete fiber bridges, stage of density increase of fiber bridges, and bridge dissipation stage. In addition, the study finds out that formation and dissipation of fiber bridges has a close relationship with sharp increase and decrease of the current.