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 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 the current development of this technology are introduced.

Introduction

As the power load gradually increases and the stability requirements of the power system become higher and higher, 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 it is currently being fully promoted. In this case, a comprehensive, objective and in-depth understanding of the technology, understanding of its current technical status, comparison and understanding of its advantages and disadvantages and relationship with the current preventive maintenance system will be of certain significance for the correct development, application and promotion of this new technology and better guarantee of the reliability and safety of power production.

1. The importance of condition monitoring and fault diagnosis technology

Transformers are important power equipment connecting power generation, transmission and distribution links. With the development of the economy and 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 the transformer is in operation, it is affected by various factors such as electricity, heat, machinery, and the environment. Its performance will gradually deteriorate and its operating status will deteriorate, which may lead to various types of failures.

In order to minimize and avoid the occurrence of faults, the traditional practice of power systems has long been to continuously research, summarize, and implement various effective regular preventive tests, maintenance and other methods. Compared with accident repair, this preventive test and maintenance method is an essential improvement. However, regular planned maintenance is blind, and preventive tests are mostly conducted offline, requiring shutdown and power outage during the test, causing economic losses. For some important equipment, it cannot be shut down easily, making it difficult to complete regular tests. Even if the equipment to be inspected can be shut down, the test results will often deviate due to the difference in the status of the transformer during operation and after shutdown. On the other hand, inspection and maintenance may cause excessive maintenance and damage the performance of the transformer.

2. Condition monitoring and fault diagnosis of transformers

Transformer fault diagnosis technology has changed from a time-based approach to a state-based approach, which includes two aspects: condition monitoring and fault diagnosis: the former provides a basis for condition maintenance by extracting characteristic signals of faults, while the latter analyzes and processes the collected status information. Research on online monitoring technology of transformers 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 quantities; (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, for condition monitoring of transformers at home and abroad, partial discharge monitoring and ultrasonic positioning technology, infrared technology, and micro-water analysis technology are mostly used. For the high-voltage bushing of the transformer, digital online measurement technology of dielectric loss factor is usually used. For on-load voltage regulating switches with many faults, an on-load fault diagnosis online device is used to measure contact wear, mechanical and electrical circuits, etc. In addition, parameters such as oil temperature, winding temperature, load current and voltage, cooling pump fan operation are also monitored. Transformer status monitoring. The main components of the transformer involved are: magnetic circuit windings and fixed insulating liquid insulation, gas insulation and cooling systems. The faults to be diagnosed are: overheating fault, discharge fault, overheating and discharge fault, mechanical failure, water ingress and moisture, etc. Commonly used partial discharge monitoring and diagnosis mostly use electrical pulse signal generation method and ultrasonic method to jointly detect electrical signals and acoustic signals to achieve ideal quantitative and positioning effects, and judge faults based on the apparent discharge amount, distribution map and location of the discharge source. The analysis of dissolved gas component content in oil (DGA) first uses various degassing principles based on the principle of dissolution equilibrium, such as vacuum, permeable membrane, gas elution, etc., to remove the gas from the oil, and then separate it with a separation column. Then, it is monitored by detectors (such as TCD, FID, etc.) or sensors of various principles to monitor different component gases. Then, based on the component ratio method or multi-dimensional diagram method commonly used at home and abroad, combined with the results of electrical tests and offline periodic tests, latent faults are comprehensively analyzed and diagnosed. Recently, technologies such as composite permeable membrane electrochemistry/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.