How to judge transformer fault casting by transformer oil

I. Common types of transformer faults

Common faults that can easily occur in transformers can be divided into two categories: common faults for charging and common faults for heat. From the development process, the common faults of distribution transformers can be divided into two categories: sudden common faults and self-limited disease common faults. The process of sudden common failures is fast, but not common. It can cause serious consequences in an instant, such as lightning strike, misoperation, load mutation, etc. There is no reasonable way to avoid sudden common faults, only through high voltage lightning arrester, relay protection devices and other methods. The occurrence probability of sudden common faults is limited to a certain range. Fault detection is mainly to diagnose and predict the common faults of such self-limited diseases.

Ⅱ, the influence of the transformation of the transformer oil characteristics on the transformer

1. Physical status changes of transformer oil
After long-term use, the tone will gradually increase, produce metal oxide and other residues, make the oil quality worse, affect the normal work of the transformer. On the other hand, after long-term use, the viscosity will become more and more viscous, resulting in heat dissipation difficulties, affecting the service life of the transformer. In this process, the interfacial tension of the oil will also be reduced, indicating that the quality of the oil becomes worse, with various metal oxides or other residues, and the safety factor of the operation of power engineering equipment is relatively reduced.

2. Chemical reactions
Transformer oil has some physical properties, including water soluble acid, acid value, moisture content and so on to reflect the working characteristics of transformer oil. Therefore, the main parameter of this physical property will immediately affect the experimental results of transformer oil. For example, the acid value reflects the quality of hydraulic oil and is also a reference for evaluating the embrittlement degree of transformer oil. According to the specific experimental results, the increase of the oleic acid value of the transformer will increase the degree of equipment damage and ultimately reduce the dielectric strength of the transformer. In the specific experimental process, the cleanliness of the appliance and its equipment will have a great influence on the measured acid value. For example, water-soluble acids are acids that dissolve water, and carbon dioxide reacts with water in the air to convert to carbonic acid. The generated carbonic acid will affect the measurement of the oleic acid value of the transformer. Therefore, if there is moisture in the transformer oil, the test experiment will affect the experimental results. This requires that the transformer oil and water before the original transformer plant can not have moisture, even in the middle and late period of transportation and storage process must also take protective measures.

3. Changes in electrical equipment characteristics
The dielectric loss factor of transformer oil can reflect the fine purification treatment level of new oil and the embrittlement degree of working oil. The dielectric loss factor of the new oil is less than 0.005. With the improvement of transformer running time, transformer oil quality will be affected by various factors, the dielectric loss factor will gradually expand. If the medium loss factor reaches a certain standard value, it indicates that the transformer oil quality has been seriously polluted and deteriorated, and the source of air pollutants should be identified and filtered to solve or consider oil change. In addition, the breakdown field strength of transformer oil is also affected by moisture content and mechanical equipment residues. When the moisture content in the oil is too large or the residue of mechanical equipment in the oil increases, the breakdown field strength will be further reduced, affecting the performance of the equipment. The operation is safe and smooth.

Ⅲ, transformer oil spectrum analysis

When the experimental data information is within the standard value range and there is no obvious improvement in development, the discriminator equipment runs normally. When the experimental data information exceeds the value of concern or is rapidly improved, the three-ratio method and gas expansion velocity are adopted to conduct in-depth analysis and identification of the internal operation status of the CT. The following is a simple description of the connotation of the relevant data information in the transformer simplification experiment. The first thing to do is to investigate the moisture. If too much water is found in the transformer, it means that the embrittlement of the transformer oil will be accelerated and the insulation strength will be affected. When the oil circuit is blocked, the temperature of the transformer part will rise, leading to fault; The occurrence of carbon dispersion will increase the probability of charging and discharging fault. When the PH is acidic, the electrical conductivity of transformer oil will increase, and the dielectric strength will decrease. In addition, through the flash point and voltage test of transformer oil, the electrical isolation charge and discharge, operation calorific value and voltage state of mechanical equipment can be determined. If any exception occurs, maintain it in time. Transformer oil conductivity will increase, dielectric strength will decrease; In addition, through the flash point and voltage test of transformer oil, the electrical isolation charge and discharge, operation calorific value and voltage state of mechanical equipment can be determined. If any exception occurs, maintain it in time. Transformer oil conductivity will increase, dielectric strength will decrease; In addition, through the flash point and voltage test of transformer oil, the electrical isolation charge and discharge, operation calorific value and voltage state of mechanical equipment can be determined. If any exception occurs, maintain it in time.
Good transformer oil should be a clean, transparent liquid, free of sediment, mechanical impurities of suspended solids and cotton material. If it is polluted and oxidized, resin and sediment will be produced, and the transformer oil will become worse, and the color will gradually turn light red until it becomes dark brown liquid.

When the transformer fails, the color of the oil will also change. In general, transformer oil is light brown, should not be reused. In addition, transformer oil can appear as cloudy milky white, oil black and dark. Transformer oil is turbid emulsion, indicating that the oil contains water. The oil color is dark, indicating that the transformer oil is aging. The oil color is black, and even has a burnt smell, indicating that there is a fault inside the transformer.