Study On Inspection Method Of Polluted Insulator Flashover Based On Acoustic Emission Technique

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.