Through the comparison of the advantages and disadvantages of the current maintenance and testing system methods, the significance of developing and applying the transformer power equipment condition monitoring and fault diagnosis technology is analyzed, the current transformer detection and fault diagnosis technology is studied, and the existing problems and development prospects of this technology are introduced.
Introduction
As the power load gradually increases, the stability requirements of the power system are increasing, and the condition monitoring and fault diagnosis technology of transformer electrical equipment has received increasing attention. More and more research and production departments are actively developing and applying this technology, and there is a comprehensive promotion trend. In this case, a comprehensive, objective and in-depth understanding of the technology, understanding its current technical status, and comparing and understanding its advantages and disadvantages and relationship with the current preventive maintenance system will be of some significance for the correct development and application of this new technology and better protection of the reliability and safety of power production.
1. The importance of condition monitoring and fault diagnosis technology
Transformers are important power equipment that connect power generation, transmission and distribution. With the development of the economy, the increase of power load and voltage level, the reliability of transformer operation has a more obvious impact on the stability of the power system. When a transformer is in operation, it is affected by various factors such as electricity, heat, machinery, and environment. Its performance will gradually deteriorate, and its operating state will deteriorate, which may lead to various failures.
In order to minimize and avoid the occurrence of faults, the traditional practice of the power system for a long time is to continuously study and summarize, and implement various effective regular preventive tests and maintenance methods. Compared with the maintenance of accidents, this preventive test and maintenance method has essential progress. However, there is blindness in regular planned maintenance, and most of the preventive tests are carried out offline. During the test, the machine needs to be shut down and the power needs to be cut off, resulting in economic losses. For some important equipment, it cannot be easily shut down, making it difficult to complete the regular test. Even if the equipment to be inspected can be shut down, the test results are often deviated due to the difference between the state of the transformer during operation and after the shutdown. On the other hand, inspection and maintenance may cause excessive maintenance and damage to the performance of the transformer.
2. Transformer condition monitoring and fault diagnosis
Transformer fault diagnosis technology has changed from a time-based approach to a state-based approach. Its content includes two aspects: condition monitoring and fault diagnosis: the former provides maintenance basis for state maintenance by extracting fault characteristic signals, while the latter analyzes and processes the collected state information. The research on transformer online monitoring technology generally includes the following contents: (1) fault mechanism analysis; (2) online monitoring means; (3) transmission, processing and storage of monitoring information; (4) extraction of fault characteristic quantity; (5) fault diagnosis methods and theoretical analysis.
The power industry mainly uses oil-filled transformers, and dry-type transformers or sulfur hexafluoride transformers are also used in some special occasions. At present, partial discharge monitoring and ultrasonic positioning technology, infrared technology, and micro-water analysis technology are mostly used for transformer condition monitoring at home and abroad. For high-voltage bushings of transformers, digital online measurement technology of dielectric loss factor is usually used. For on-load voltage regulating switches with many faults, on-load fault diagnosis online devices are used to measure touchpoint wear and mechanical and electrical circuits. In addition, parameters such as oil temperature, turn winding temperature, load current and voltage, and cooling pump fan operation are also monitored. Transformer status monitoring involves the main components of the transformer: magnetic circuit windings and insulation of fixed insulating liquids, gas insulation and cooling systems. The faults to be diagnosed are: overheating fault, discharge fault, overheating and discharge fault, mechanical fault and water ingress dampness, etc. The commonly used partial discharge monitoring and diagnosis method mostly uses the electric pulse signal generation method and the ultrasonic method. The ideal quantitative and positioning effect of the joint detection of electrical and acoustic signals can be judged according to the apparent discharge power, distribution pattern and the positioning of the discharge power source. The analysis of dissolved gas component content (DGA) in oil is firstly based on the principle of dissolution equilibrium. Various principles are used for degassing, such as vacuum, permeable membrane, gas elution, etc. The gas in the oil is removed, and then separated by a separation column. Then the different component gases are monitored by detectors (such as TCD, FID, etc.), or sensors of various principles. After that, according to the common component ratio method at home and abroad or multi-dimensional graphic method, combined with the results of electrical tests and offline regular tests, latent faults are comprehensively analyzed and diagnosed. Recently, technologies such as composite permeable membrane electrochemical/fuel cell infrared monitoring have been developed to analyze the content of dissolved gas components in oil. Since the accuracy of DGA analysis and judgment has been recognized at home and abroad, this technology has become a research hotspot in various countries.
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