Research On An Intellectual Fault Diagnosis System For Power Transformer Based On Dissolved Gas Analysis Technology

Power transformer is one of the most important electrical equipments in the electric system, and is also one of the electrical equipments resulting in most electric system accidents. Its operating state affects system's security level directly. It is an important issue for electrical department to find the potential faults of the transformer, to keep it operating safely, and to improve the reliability of power supply. Therefore, it is of great realistic significance to study the fault diagnosis technology of transformer and to increase the operating and maintaining level of transformer.Dissolved Gases Analysis (DGA) is an important means to diagnose the internal fault of transformer and it offers an important basis to find the general incipient faults in the transformer indirectly. It has been proved in practice that the DGA technology is very effective to find the potential faults and the developing trend in the transformer. Thus, the DGA technology has been placed in an important position in the preventive tests of power transformer equipment.Transformer fault is the result of transformer itself and its synthesized action of application environment and long-term accumulation. So the fault symptoms of transformer are various, and the relation between the fault symptoms and fault mechanics is also complicated, which make it very difficult to establish a universal fault diagnosis method for transformer. Fault diagnosis of transformer is to determine the fault character or position according to the fault symptoms of transformer. Because of the complexity of transformer fault, the diagnosis process must use multiform methods, not a single method. Therefore, we must search for principles, methods and means, which are helpful to fault diagnosis of transformer from all kinds of subjects. So it makes the fault diagnosis technology takes on a characteristic of multi-subject cross.With the rapid development of computer technology and artificial intelligence theory, intellectual technologies such as Expert System and Artificial Neural Network, have broken a new path to fault diagnosis for knowledge engineers. Expert System is a main form to realize artificial intelligence, and is one of the most active and widespread application realms of artificial intelligence's application research. Whereas the fault diagnosis of transformer isspeciality, experience and complexity, adopting Expert System diagnosis method is of unique predominance. Therefore, in the paper the contents of dissolved gases have been selected as characteristic parameters, and all kinds of artificial intelligence technology is adopted to the study of fault diagnosis system for power transformer insulation. Four main parts are included in the paper.Firstly, the initial diagnosis of power transformer fault character is studied. In order to make DGA technology play a more important role in transformer fault diagnosis, and improve the veracity of the EEC three-ratio method, visual technology is integrated with fuzzy diagnosis technology to establish a visual fuzzy diagnosis system for power transformer insulation fault, which is based on IEC three- ratio method. By introducing visual technology, a 3D /2D visual transformer fault diagnosis model based on database is established. According to the DGA test data of transformer, this system can display the operating state of transformer in the fault space and the fault type of the transformer directly. It simplifies the calculations greatly comparing to the conventional diagnosis method. By introducing fuzzy diagnosis technology, fuzzy transaction is done to IEC three-ratio method, which can describe the coding characteristic of the DGA test data of the oil-immersed transformer more accurately. By integrating the visual technology with the fuzzy diagnosis technology, it avoids some inevitable problems such as faulty diagnosis and flawed diagnosis encountered in the past with mono-method.Secondly, the research on how to confirm the fault character of power transformer is made in the paper. It includes a poten...