IMPROVEMENT OF HIGH VOLTAGE DC INSULATING SYSTEM AND ITS LIFE-TIME ESTIMATION

利用空间电荷分布探测系统，定量研究了直流绝缘系统空间电荷特性与绝缘性能之间的关系。为直流固体绝缘材料的发展提供了指导。主要研究结果如下：低密度聚乙烯（ldpe）及其共混聚合物是一种新型高压直流电缆材料，其空间电荷特性和直流击穿强度与聚丙烯的形态、添加剂和共混密切相关。此外，通过改变ldpe的密度可以控制空间电荷现象。ldpe中的空间电荷由从电极注入的载流子控制。半导电电极比金属电极更容易注入载流子。澄清了聚酰亚胺、聚对苯二甲酸乙二醇酯和聚四氟乙烯中的空间电荷现象。特别是聚酰亚胺表面吸附的水分，使聚酰亚胺的空间电荷增强。利用局部放电（pd）测量系统和频谱分析仪，构建了一套新的绝缘退化诊断系统。将该系统与高速图像增强器结合使用，得到了以下结果：利用该诊断系统测量了ldpe中放电模式、放电电流和空穴频谱随时间的变化，并对放电老化机理进行了讨论。通过这些结果，指出pd法对高分子绝缘材料的寿命估计是强有力的。树形通道的pd特性和发光图像随时间的变化与聚合物材料的pd降解密切相关。这些结果有助于阐明电树的产生和发展机制，也有助于改进聚合物材料的寿命估计。这些结果对提高直流绝缘系统的性能和寿命估计的可靠性具有重要意义。

BY USING THE SPACE CHARGE DISTRIBUTION PROBING SYSTEM, THE RELATIONSHIP BETWEEN SPACE CHARGE CHARACTERISTICS AND PERFORMANCE OF DC INSULATION SYSTEM WERE STUDIED QUANTITATIVELY. A GUIDELINE FOR THE DEVELOPMENT OF DC SOLID-INSULATING MATERIAL WAS OBTAINED. THE MAIN RESULTS ARE AS FOLLOWS.1. SPACE CHARGE CHARACTERISTICS AND DC BREAKDOWN STRENGTH OF LOW-DENSITY POLYETHYLENE (LDPE) AND ITS BLEND POLYMERS WHICH ARE REGARDED AS NEW MATERIALS FOR HIGH-VOLTAGE DC POWER CABLES, ARE CLOSELY RELATED TO MORPHOLOGY, ADDITIVE, AND BLENDING OF POLYPROPYLENE. FURTHERMORE, THE SPACE CHARGE PHENOMENA CAN BE CONTROLLED BY CHANGING DENSITY OF LDPE.2. SPACE CHARGE IN LDPE IS GOVERNED BY CARRIERS INJECTED FROM THE ELECTRODES. THE SEMI-CONDUCTIVE ELECTRODE CAN INJECT CARRIERS MORE EASILY THAN THE METAL ELECTRODE.3. THE SPACE CHARGE PHENOMENA ARE IN POLYIMIDE, POLYETHYLENE TEREPHTHALATE AND TEFLON FEP WERE CLARIFIED. ESPECIALLY, SPACE CHARGE IN POLYIMIDE WAS ENHANCED BY WATER ABSORBED ON THE SURFACE.A NEW DIAGNOSTIC SYSTEM FOR INSULATION DEGRADATION WAS CONSTRUCTED WITH THE PARTIAL DISCHARGE (PD) MEASUREMENT SYSTEM AND SPECTRUM ANALYZER. BY USING THE SYSTEM AND A HIGH-SPEED IMAGE INTENSIFIER THE FOLLOWING RESULTS WERE OBTAINED.4. PD PATTERNS AND PD CURRENTS AND THE FREQUENCY SPECTRA OF A VOID IN LDPE WERE MEASURED WITH TIME BY USING THE DIAGNOSTIC SYSTEM THE AGING MECHANISMS WERE ALSO DISCUSSED. THROUGH THESE RESULTS, PD WAS POINTED OUT TO BE POWERFUL FOR THE LIFETIME ESTIMATION OF POLYMER INSULATING MATERIALS.5. THE CHANGES WITH TIME OF THE PD CHARACTERISTICS AND LIGHT EMISSION IMAGES OF TREE CHANNELS WERE CLOSELY RELATED TO THE PD DEGRADATION OF POLYMERIC MATERIALS. THESE RESULTS WERE USEFUL TO CLARIFY THE MECHANISMS FOR THE INCEPTION AND DEVELOPMENT OF ELECTRICAL TREES AND ALSO TO IMPROVE THE LIFETIME ESTIMATION OF POLYMERIC MATERIALS.THESE RESULTS GREATELY CONTRIBUTED TO THE IMPROVEMENT OF THE PERFORMANCE OF DC INSULATING SYSTEMS AND THE RELIABILITY OF LIFETIME ESTIMATION.