Transformer condition monitoring and fault diagnosis

By comparing the advantages and disadvantages of the current maintenance and detection system methods, the significance of developing and applying the condition monitoring and fault diagnosis technology of transformer type power equipment 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

With the gradual increase of power load, power system stability requirements are increasing day by day, transformer electrical equipment condition monitoring and fault diagnosis technology is increasingly popular attention, more and more research, production departments are actively developing and applying this technology, has been a trend of comprehensive promotion. In this case, a comprehensive, objective and in-depth understanding of the technology, understand its current technical status, compare and understand its advantages and disadvantages and relations with the current preventive maintenance system, for the correct development, application and promotion of this new technology and better guarantee of the reliable safety of electric power production will have a certain significance.

1. Importance of condition monitoring and fault diagnosis techniques

Transformer is an important power equipment connecting the link of power generation, transmission and distribution. With the development of economy and the increase of power load and voltage level, the reliability of transformer operation has more obvious influence on the stability of power system. Transformer in operation, affected by electrical, thermal, mechanical, environmental and other factors, its performance will gradually deteriorate, the running state deteriorates, may lead to all kinds of failures.

In order to minimize and avoid the occurrence of faults, the traditional practice of power system for a long time is to constantly study, summarize, implement a variety of effective regular preventive tests, maintenance and other ways. Compared with accident maintenance, this kind of preventive test and maintenance has essential progress. However, scheduled maintenance is blind, and most of the preventive tests are off-line, the test needs to stop, power off, resulting in economic losses. For some important equipment, it cannot be easily shut down, making it difficult to complete regular tests. Even if the equipment to be checked can be stopped, the test results will be biased due to the difference in transformer status between operation and outage. On the other hand, inspection and maintenance may cause excessive maintenance and damage the transformer performance.

2. Transformer condition monitoring and fault diagnosis

The transformer fault diagnosis technology changes from the time-based way to the state-based way, which includes 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 of transformer on-line 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 feature quantity; (5) Fault diagnosis methods and theoretical analysis.

The power industry mainly uses oil-filled transformer, in some special occasions also uses dry transformer or sulfur hexafluoride transformer. At present, partial discharge monitoring and ultrasonic positioning technology, infrared technology, micro-water analysis technology are used for transformer status monitoring at home and abroad. Digital on-line measurement technology of dielectric loss factor is usually used for high voltage bushing of transformer. For on-load voltage regulator with many faults, on-load fault diagnosis on-line device is used to measure contact wear and mechanical and electrical circuits. In addition, oil temperature, winding temperature, load current and voltage, cooling pump fan operation and other parameters are also included in the monitoring transformer state monitoring. The main parts of the transformer involved are: magnetic circuit winding and fixed insulation liquid insulation, gas insulation and cooling system. The faults to be diagnosed are: overheating fault, discharge fault, overheating and discharge fault, mechanical fault and water dampness. In common PD monitoring and diagnosis, electrical pulse signal generation method and ultrasonic method are used to detect electrical signal and sound signal to achieve the ideal quantitative and positioning effect, and the fault can be judged according to the apparent discharge quantity, distribution diagram and location of discharge power source. To analyze the content of dissolved gas components in oil (DGA), firstly, degassing is carried out on various principles according to the principle of dissolution equilibrium, such as: Vacuum, permeable membrane, gas elution, etc., the gas in the oil is removed, and then separated by the separation column, and then monitored by the detector (such as TCD, FID, etc.), or various principles of the sensor for different components of the gas monitoring, according to the general component ratio method at home and abroad or multidimensional view method, combined with electrical test and off-line periodic test results, The latent fault was diagnosed by comprehensive analysis. Recently, the composite permeable membrane electrochemical/fuel cell infrared monitoring technology has been developed to analyze the content of dissolved gas components in oil. As the accuracy of DGA analysis and judgment has been recognized at home and abroad, the technology has become a research hotspot in many countries.