操作冲击电压累积作用下油纸绝缘的损伤与特性研究

发布时间：2018-02-10 01:43

本文关键词： 油纸绝缘操作过电压损伤生成物电气特性机械特性 V-N特性　出处：《重庆大学》2014年硕士论文　论文类型：学位论文

【摘要】：变压器作为电网的核心设备，对电网安全运行起着重要作用。研究表明导致变压器失效的主要原因是其油纸绝缘的老化，油纸绝缘的老化是由温度，电场，水分和氧气等各种因素共同造成的。要准确监测变压器油纸绝缘的状态，就必须尽可能地了解每一种老化因素所能造成的损伤。在这些老化因素中，过电压对于油纸绝缘的影响是不可忽略的，，但关于过电压对于油纸绝缘的损伤方面的研究还比较少且主要集中在雷电过电压方面，对于操作过电压对油纸绝缘的影响方面的研究还鲜见报到。本文通过建立操作冲击电压对油纸绝缘的损伤试验平台，研究了操作冲击电压作用下油纸绝缘的损伤以及机械特性和电气特性的变化规律。试验结果表明，在操作冲击电压的作用下，绝缘纸的表面会产生沿面的火花与电弧放电，放电会使得绝缘油中的H2以及烃类气体含量上升，同时产生的极性物质会使得绝缘油的介电常数和介质损耗在低频区上升并使其电导率增大，但对绝缘油的击穿特性与局部放电特性几乎没有影响。另外，绝缘纸表面的沿面放电还会使得绝缘纸的表面电导率上升，导致其沿面放电起始电压降低。操作过电压还会使得绝缘纸内部的分子链发生断裂，使得其聚合度下降，并使其介电常数与损耗在低频部出现上升，操作冲击击穿电压发生下降，但其工频击穿特性没有发生明显变化，直流体积电导率也仅仅是轻微上升。为了更加深入的研究油纸绝缘对操作冲击电压的耐受能力，本文也对操作冲击电压作用下油纸绝缘的击穿寿命与电压幅值的关系（V-N特性）进行了研究，并研究了油纸绝缘的老化状态以及操作冲击电压的波形变化对其V-N特性的影响。研究发现：随着油纸绝缘老化程度的加深，油纸绝缘的操作冲击耐受能力会出现下降趋势，且这种趋势在老化的初期下降较慢，而在老化的中后期下降较快；冲击电压的波形变化也会对油纸绝缘的操作冲击耐受能力造成影响，波头时间的变短与波尾时间的变长均会使得油纸绝缘在的操作冲击耐受能力下降，但波头时间变化对油纸绝缘冲击耐受能力的影响要高于波尾时间变化。
[Abstract]:As the core equipment of the power network, transformer plays an important role in the safe operation of the power network. The research shows that the main cause of transformer failure is the aging of its oil-paper insulation, and the aging of oil-paper insulation is caused by temperature and electric field. In order to accurately monitor the condition of oil paper insulation of transformers, it is necessary to understand as far as possible the damage caused by each ageing factor. The influence of overvoltage on oil-paper insulation can not be ignored, but the research on the damage of overvoltage to oil-paper insulation is relatively few and mainly focuses on lightning overvoltage. Research on the effect of operating overvoltage on oil-paper insulation is rare. In this paper, the damage and mechanical and electrical characteristics of oil-paper insulation under the action of operating impulse voltage are studied by setting up the damage test platform of operation impulse voltage. The experimental results show that, Under the action of the operating impulse voltage, the surface of the insulator paper will produce spark and arc discharge along the surface, and the discharge will increase the H _ 2 and hydrocarbon gas content in the insulating oil. At the same time, the dielectric constant and dielectric loss of insulating oil will increase in the low frequency region and the conductivity will increase, but the breakdown characteristics and partial discharge characteristics of insulating oil will have little effect on the dielectric constant and dielectric loss of the insulating oil. In addition, the dielectric constant and dielectric loss of the insulating oil will increase in the low frequency region. The surface discharge on the surface of the insulator paper will also increase the surface conductivity of the insulator paper, resulting in the decrease of the initial voltage of discharge along the surface. The operating overvoltage will also break the molecular chain inside the insulator paper and decrease the degree of polymerization. The dielectric constant and loss increase in the low frequency part, the operating impulse breakdown voltage decreases, but the power frequency breakdown characteristic does not change obviously, and the DC volume conductivity is only slightly increased. In order to further study the resistance of oil-paper insulation to operating impulse voltage, the relationship between breakdown life and voltage amplitude of oil-paper insulation under operation impulse voltage is also studied in this paper. The effects of aging state of oil-paper insulation and waveform change of operating impulse voltage on V-N characteristics of oil-paper insulation are studied. It is found that with the aging degree of oil-paper insulation, the operating impact resistance of oil-paper insulation will decrease. This trend decreases slowly in the early stage of aging, but decreases more rapidly in the middle and late stage of aging. The waveform changes of impulse voltage will also affect the operating impact resistance of oil-paper insulation. The shorter the wave head time and the longer the wave tail time, the lower the operating impact resistance of the oil-paper insulation, but the influence of the wave head time on the impact resistance of the oil-paper insulation is higher than the change of the wave-end time.
【学位授予单位】：重庆大学
【学位级别】：硕士
【学位授予年份】：2014
【分类号】：TM41

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