Technology Literature

How to judge transformer fault by transformer oil?

1. Common fault types of transformers
The common faults that transformers are prone to occur can be divided into two categories: charging common faults and thermal common faults. From the perspective of the development process, the common faults of distribution transformers can be divided into two categories: sudden common faults and self-limiting 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 arresters, relay protection devices and other methods. The 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-limiting diseases.

2. The influence of the change of transformer oil characteristics on the transformer
a. Physical state change transformer oil
After long-term use, the color tone will gradually increase, resulting in residues such as metal oxides, which will deteriorate the oil quality and affect the normal operation of the transformer. On the other hand, after long-term use, its viscosity will become more and more viscous, making it difficult to dissipate heat and affecting the service life of the transformer. During this process, the interfacial tension of the oil will also decrease, indicating that the quality of the oil is poor, with various metal oxides or other residues, and the safety factor of the operation of the power engineering equipment is relatively reduced.

b. Chemical reactions

Transformer oil has some physical properties, among which water-soluble acid, acid value, moisture content, etc. will 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 degree of embrittlement of transformer oil. From the specific experimental results, the increase of the acid value of the transformer oil will increase the degree of equipment damage, and ultimately reduce the dielectric strength of the transformer. During a specific experiment, the cleanliness of the utensils and their equipment can have a great impact on the measured acid value. For example, a water-soluble acid refers to an acid that dissolves water, and carbon dioxide reacts with water in the air to convert to carbonic acid. The resulting carbonic acid affects the measurement of the acid value of the transformer oil. 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 cannot contain moisture, and protective measures must be taken even in the middle and later transportation and storage process.



c. Changes in the characteristics of electrical equipment
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 new oil is lower than 0.005. With the increase of the operating time of the transformer, the oil quality of the transformer will be affected by various factors, and the dielectric loss factor will gradually expand. If the dielectric loss factor reaches a certain standard value, it means that the transformer oil has been seriously polluted and deteriorated. The source of air pollutants should be identified and filtered to solve or consider changing the oil. In addition, the breakdown field strength of transformer oil is also affected by moisture content and mechanical equipment residues. When the water content in the oil is too large or the residue particles of the mechanical equipment in the oil increase, the breakdown field strength will be further reduced, affecting the performance of the equipment. Safe and smooth operation.

d. Chromatographic analysis of transformer oil

When the experimental data information is within the standard value range and there is no obvious improvement in the development, the discriminator equipment operates normally. When the experimental data information exceeds the concern value or improves rapidly, the three-ratio method, flatulence velocity, etc. are used to conduct in-depth analysis and identification of the internal operating conditions of the current transformer. The following is a brief 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 it is found that there is too much moisture 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 failure; the occurrence of scattered carbon will increase the probability of charging and discharging failure of the transformer; and when the PH is acidic, the electrical conductivity of the transformer oil will increase, and the dielectric strength will increase. In addition, through the open flash point and withstand voltage test of transformer oil, the electrical isolation charge and discharge, operating calorific value and withstand voltage state of mechanical equipment can be determined. If there is any abnormality, it should be maintained in time. 

The electrical conductivity of transformer oil will increase and the dielectric strength will decrease; in addition, through the open flash point and withstand voltage test of transformer oil, the electrical isolation charge and discharge, operating calorific value and withstand voltage state of mechanical equipment can be determined. If there is any abnormality, it should be maintained in time. The electrical conductivity of transformer oil will increase and the dielectric strength will decrease; in addition, through the open flash point and withstand voltage test of transformer oil, the electrical isolation charge and discharge, operating calorific value and withstand voltage state of mechanical equipment can be determined. If there is any abnormality, it should be maintained in time.


A good transformer oil should be a clean, transparent liquid, free of suspended solids and cotton-like substances of sediment, mechanical impurities. If it is polluted and oxidized, resulting in resin and sediment, the transformer oil quality will deteriorate, and the color will gradually become light red until it becomes a dark brown liquid.

When the transformer fails, the color of the oil also changes. Under normal circumstances, when the transformer oil is light brown, it should not be reused. In addition, transformer oil can appear cloudy milky white, oil black and dark. Transformer oil is cloudy and milky, indicating that the oil contains moisture. The darker oil color indicates 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.