【作者】 王新超；

【导师】 苏秀苹；

【作者基本信息】 河北工业大学 ， 电气工程， 2010， 博士

【摘要】 在我国中压配电系统中,广泛采用中性点小电流接地方式。做好小电流接地系统运行的状态监测工作,对于保障生产用电和人民生活用电的可靠、安全性具有重大意义。本文主要针对小电流接地系统中状态监测的一些特点,通过理论推导、现场数据记录验证、模拟分析和仿真等方法对线路绝缘在线监测的实现、接地故障线路的甄别和电气设备状态的温度解读算法等方面进行了研究,完成了如下研究工作:本文就不停电绝缘在线监测问题进行了研究,借助电磁场和行波理论,提出了一种基于短暂扰动注入的输配电线路状态在线监测新方法。该方法可以完全实现线路绝缘的带电在线监测;通过分叉点注入和电压的短暂钳位技术,实现了各分支线路的独立监测。本文针对消弧线圈接地系统在单相接地故障时故障线路甄别困难问题,提出了零序电流比例增量判别法。该方法利用故障线路零序电流变化率大于非故障线路的原理来实现线路甄别。本文还构建了基于多种故障线路甄别算法综合的模糊判据体系,实例分析表明该体系可以有效提高算法的可靠性。本文研究了两相接地时主要电气量的变化,提出了将负序电流检测法用于单相接地异相高阻接地(漏电)故障的线路甄别。本文在对温度时域传导过程分析的基础上,提出了一种在线监测设备中电接触元件电阻变化的时域参考模型法。该方法可根据经验来选择近似的参考模型,只获取温度的快速变化信号,对变化缓慢的环境温度不敏感。本文在对温度传导过程频域分析的基础上,给出了温度传递延滞时间的频域相角表达式。借助Daubechies小波,研究了温度变化的时频域信息提取方法。该方法对于评估装置内耗电阻的变化十分有效。更多还原

【Abstract】 In China, small current grounding system has been used in most of the medium voltage power distribution networks. Therefore, to monitor the conditions of the small current grounding system and detect the possible failurs in the distribution lines is of great significance to ensure a reliable electricity supply for industrial and domestic customers.This paper has mainly focused on the characteristics of the small current grounding system and its condition monitoring. By means of theoretical analysis, simulations and practical field data validations, researches have been carried out on some related topics as: online inspection of insultaion conditions, grounding-fault line screening and detection, and algorithmes for using temperature to intepret the conditions of electric devices.This paper has studied how to monitor the insulation conditons of a power system at online circumstances. It suggests a new short-time disturbance method for state monitoring of the power transmission and distribution lines using electromagnetic field and wavelet transform theories. The method has the characteristics of being able to realize online monitoring of possible insulation problem. By injection through the bifurcate points using voltage transient clamping technology, it can achieve independent monitoring of all branch lines.This paper gives a new screening method based on the ratio of current increment at the zero sequence. Because the current change ratio of the zero sequence in the fault line is greater than other normal lines, the fault line can be easily detected. The advantage of the method is that it is suitable for all neutral point grounding systems. Furthermore, through theoretical analysis and derivation, a multi-algorithm based fuzzy screening system is constructed for the detection of fault lines. A verification example shows that the system can effectively improve the reliability of the result than each individual algorithm does.In this paper, the changes of major electrical parameters in the two-phase grounding case are discussed. It also suggests a negative sequence current detection method to discover the fault in the case of one single-phase ground and another phase with high impedance grounding problem (current leakage). Based on the analysis how temperature is transmitted within time domain, a reference model in time domain is suggested to monitor the electrical contact resistance changes in a power device. This method uses experience data to select the reference model. It only responds to rapid changes in the temperature of the device but is not so sensitive to the slow variations in the environment temperature.This paper has also studied temperature transmission in the frequency domain. A frequency phase expression is deduced to describe the time delay of temperature transmission in the frequency domain. This paper has made further study about using Daubechies wavelets method to extract temperature changes from both time and frequency domains. The method shows to be very useful for assessing the internal loss resistance of the electric devices.更多还原