变压器实测雷电侵入波统计及其对油纸绝缘性能影响研究

发布时间：2018-06-26 06:04

本文选题：变压器 + 雷电侵入波　；参考：《重庆大学》2014年硕士论文

【摘要】：变压器是电力系统的核心设备，它的安全运行关乎整个电力系统的可靠性。在决定变压器雷电冲击绝缘水平时，较为精确地掌握变压器上的实际雷电过电压水平是合理选择设备绝缘配合的前提。而目前，有关站内变压器雷电侵入波统计规律分析及其对变压器内绝缘影响的研究较少，变压器绝缘设计和耐压测试仍然采用传统的标准雷电波，而实际作用在变压器上的雷电侵入波却是非标准的波形。鉴于此，研究变压器实测雷电侵入波的统计规律以及实测雷电侵入波对变压器油纸绝缘性能的影响不仅能够完善有关雷电波的理论研究，更能为变压器合理的绝缘设计以及站内雷电防护提供技术依据和支撑，具有重要的理论价值和工程实用价值。首先，本文基于某110kV变压器上长达六年的雷电侵入波监测数据，利用数字滤波技术，提取了侵入波的有用信号，提出采用能量法和DE法求取侵入波的时间参数，并对时间参数进行统计分析。统计结果表明：变压器雷电侵入波为衰减振荡的电压波形，，其振荡主频主要集中在10kHz以内；侵入波的波头时间和波尾时间均比标准雷电波长，且时间参数服从对数正态分布规律；波头时间和波尾时间具有较强的相关性，二者的相关性可用一个带状区域表示。然后，搭建了冲击过电压试验平台，基于雷电侵入波的统计结果，选取具有50%概率的实测雷电侵入波(20/198μs)和标准雷电波展开对比试验，并研究不同过电压时间参数对油纸绝缘50%击穿电压的影响。试验结果表明：在1.2~26μs的试验波头时间范围内，绝缘纸的50%击穿电压与过电压波的波头时间关系较大，而波尾时间对50%击穿电压的影响不大。且绝缘纸的厚度、层数以及老化程度不同时，过电压时间参数对绝缘纸50%击穿电压的影响程度不同。最后，基于COMSOL Multiphysics有限元仿真软件，建立了油纸绝缘仿真模型，计算了油纸绝缘介质在过电压作用下的电位分布和电场分布，以及在不同时间参数过电压作用下油纸绝缘系统接地极流过的电流。仿真结果表明：当正极性过电压作用时，流过绝缘系统的电流分为正负极性两个部分，存在正极性最大值和负极性最大值，且以位移电流为主。正极性电流的大小主要与冲击电压的波头部分的电压变化率有关；负极性电流的大小主要与冲击电压的波尾部分的电压变化率有关。正极性电流的最大值始终明显大于负极性电流的最大值，因此，当正极性过电压作用时，正极性电流是影响绝缘介质电气性能的主要因素。
[Abstract]:Transformer is the core equipment of power system, its safe operation is related to the reliability of the whole power system. When determining the lightning impact insulation level of transformers, it is the premise of reasonable selection of equipment insulation to accurately grasp the actual lightning overvoltage level on the transformer. At present, there are few studies on the statistical law of lightning intrusion wave and its influence on transformer insulation, and the traditional standard lightning wave is still used in transformer insulation design and voltage withstand test. But the actual action on the transformer lightning intrusion wave is a non-standard waveform. In view of this, the study on the statistical law of the measured lightning intrusion wave and the effect of the measured lightning intrusion wave on the insulation performance of transformer oil paper can not only improve the theoretical research on the lightning wave. It can provide technical basis and support for reasonable insulation design of transformer and lightning protection in station. It has important theoretical value and practical value in engineering. Firstly, based on the monitoring data of lightning intrusion wave on a 110kV transformer for six years, the useful signal of intrusion wave is extracted by digital filtering technique, and the time parameter of intrusion wave is obtained by energy method and DE method. The time parameters are analyzed statistically. The statistical results show that the transformer lightning intrusion wave is the voltage waveform of attenuation oscillation, and its main oscillation frequency is mainly less than 10 kHz, and the wave head time and wave tail time of the intrusive wave are both higher than those of the standard lightning wave length. The correlation between the wave head time and the wave tail time can be expressed in a zonal region. Then, an impulse overvoltage test platform is set up. Based on the statistical results of lightning intrusion wave, a 50% probability lightning intrusion wave (20 / 198 渭 s) and a standard lightning wave are selected to carry out a comparative test. The effect of different overvoltage time parameters on 50% breakdown voltage of oil-paper insulation was studied. The experimental results show that in the range of 1.2 ~ 26 渭 s, the 50% breakdown voltage of the insulator paper is closely related to the time of the overvoltage wave, but the wave tail time has little effect on the 50% breakdown voltage. The thickness, the number of layers and the aging degree of the insulator paper are different, and the influence of the overvoltage time parameters on the 50% breakdown voltage of the insulator paper is different. Finally, based on COMSOL Multiphysics finite element simulation software, the simulation model of oil-paper insulation is established, and the potential distribution and electric field distribution of oil-paper insulating medium under the action of overvoltage are calculated. And under the action of different time parameter overvoltage, the current of the earth pole of oil-paper insulation system. The simulation results show that when the positive polarity overvoltage is applied, the current flowing through the insulation system can be divided into two parts: positive and negative polarity, and the displacement current is the main one. The magnitude of positive current is mainly related to the rate of voltage change in the head part of impulse voltage, and the magnitude of negative current is mainly related to the rate of change of voltage in the end part of impulse voltage. The maximum value of positive current is always larger than that of negative current. Therefore, the positive current is the main factor affecting the electrical performance of insulating dielectric when the positive overvoltage is applied.
【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】：TM862

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