【作者】 李明；

【导师】 舒乃秋；

【作者基本信息】 武汉大学 ， 电力系统及其自动化， 2004， 硕士

【摘要】 在长期的运行过程中绝缘子表面会积累污秽，遇到潮湿的气候条件容易发生污秽放电，造成污闪事故，它通常会造成大面积停电，这对强调安全和稳定的电力系统来讲是不能接受的，为此电力部门采取多种措施来防止污闪的发生。目前使用的方法以预防为主，但实践证明这是不够的，还应该对污染严重的地区的绝缘子进行监测，及时了解污秽的严重程度和它对系统的威胁程度，主动展开绝缘子污闪的防治工作，有针对性的采取措施，提高工作效率，减少污闪事故发生的可能性，因此绝缘子污秽放电在线监测具有很大的社会效益和经济效益，是一项具有重大技术经济意义的研究课题。 在查阅国内外大量参考文献的基础上，本文分析了现有的检测方法的特点和不足，并提出基于声发射技术的绝缘子污秽放电监测方法。通过分析绝缘子污秽放电过程以及伴随放电出现的声发射现象，研究了污秽放电发展过程中声信号的特点，揭示出污秽放电的严重程度和声信号之间存在的关系，提出通过监测绝缘子污秽放电发出的声信号可以实现对绝缘子污秽的在线监测。 为了能够捕捉污秽放电产生的声信号，设计了具有较高灵敏度的聚焦声传感器及试验用数据采集电路，聚焦声传感器是将压电传感器和聚焦抛物面组合在一起，可以接收到较远处放电产生的微弱声信号。使用这套装置，在绝缘子的人工污秽试验中采集了不同污秽度和不同电压下绝缘子污秽放电的声发射信号，对比污秽放电不同阶段的声发射信号，证明随着污秽放电的增强，声信号幅值增大并且连续性更强。 最后运用模糊推理的方法对试验数据进行分析和处理，结果证明通过声信号可以定量地判断出放电距离污闪的裕度，证明本文提出的声学监测法可以真正实现绝缘子在线监测，能正确判断绝缘子污秽程度，并发出相应的报警信号，使工作人员能够及时采取措施，避免污闪事故的发生。 本文提出的声学监测法是声发射技术在电力系统中的一个应用，是绝缘子污秽在线监测的一种新方法。本文所完成的仅是一些基础工作，还需要进行大量的试验和研究才能使之完善并达到实用的程度。更多还原

【Abstract】 Insulators on power distribution lines will be covered with filth during the long field operating time and flashover will happen under humidity conditions. Flashover will cause power cut in large area and endanger the security and stability of power system. To prevent flashover accident, lots of methods have been taken. However, at present, these methods are mainly precautionary, and practices prove that they are not enough. The insulator pollution monitoring is also needed in severely polluted areas. Thus, the severity of pollution and its dangerousness to power system can be known in time, and preventive measures can be taken efficiently in order to decrease the possibility of flashover accident. So the on-line monitoring of insulator contaminant discharge possesses great social and economic benefit. It is an important study area in electrical engineering.Based on large amount of literatures, some typical methods of inspecting insulator contamination are summarized in. Their advantages, disadvantages and their application status are also discussed respectively in detail. By analyzing the discharge process of polluted insulator and concomitant acoustic emission phenomenon, the characteristics of acoustic signal are studied, and the relationship between discharge and acoustic signal is revealed in this paper. A new method of insulator discharge monitoring based on the acoustic emission technique is put forward.In order to catch the acoustic signal produced by contaminant discharge, a focused acoustic sensor with high sensitivity and data collecting circuit are designed. The focused acoustic sensor combined by piezoelectric sensor and focused paraboloid can receive weak acoustic signal emitted by discharge at a distance. The acoustic emission signal under different contamination level and different voltage grade are collected in the insulator’s artificial pollution test by using this set of equipment. By comparing the acoustic emission signal during different phase of contaminant discharge, it proved that the amplitude and continuity of acoustic signal increase along with the boost up of contaminant discharge.At last, the data obtained in the experiments are analyzed using fuzzy mathematics tools, and results prove that the capacitance between discharge and flashover can be calculated by the acoustic signal. It also proved that the ultrasonic monitoring method can indeed realize the on-line monitoring of insulator, and correctly judge the contamination level of insulator. The device can send out correspondent alarm signal, in order that the flashover accident can be avoided by adopting correct measures in time.The ultrasonic monitoring method is an application of acoustic emission in power system, and it is a new method of on-line insulator contamination monitoring. Because only some basic work has been accomplished in this paper, more experiments and further study are needed to make it better and practical.更多还原