Transformer oil is a fractionated substance of petroleum. During the operation of the transformer, the transformer oil fully plays the role of insulating layer, heat removal and magnetic blowing. Because of its insulating effect, transformer oil can protect the energized part, thereby reasonably avoiding short-circuit fault conditions. In addition, transformer oil, or an excellent heat-removing agent, will inevitably generate a lot of heat during the operation of the transformer. Transformer oil can reasonably absorb the heat generated by the transformer, and then has a cooling effect on the equipment. In addition, during the operation of the electrical equipment, the opening of the power switch equipment will cause the occurrence of electric isolation, and the use of transformer oil here can reasonably solve the electric isolation. As far as the transformer equipment itself is concerned, it has the maintenance function of transformer oil, and various components in it, such as iron cores, electromagnetic coils, etc., are not easy to be rapidly mildewed by the corrosion of gas and moisture, thereby preventing moisture return or rusting. , to a certain level, the service life of each component of the equipment is increased, and the safety and reliability of the equipment operation is improved.
Transformer Oil Analysis
1. Common fault types of transformers
The common faults that are very prone to transformers can be divided into two categories: charge common faults and thermal common faults. In terms of the development process, the common faults of distribution transformers can be divided into two categories, namely, sudden common faults and self-limiting disease common faults. The process of sudden common faults is rapid, but it is not common. It can lead to serious effects in an instant, such as lightning strikes, operating errors and sudden changes in the load, etc. There is no reasonable way to avoid sudden common faults, only through methods such as high-voltage arresters and relay protection devices. The probability of occurrence of sudden common faults is limited to a certain range. Fault detection is mainly for the diagnosis and prediction of common faults of such self-limiting diseases. Generally speaking, common faults of self-limiting diseases can be divided into three categories, namely, the overtemperature of the transformer part and the embrittlement of the transformer insulating layer and its internal partial discharge.
2. The influence of the transformation of transformer oil characteristics on the transformer
2.1 Physical state changes
After long-term use, the color tone of the transformer oil 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 thicker and thicker, which will cause difficulty in heat removal and affect the service life of the transformer. In this process, the interfacial tension of the oil will also decrease, indicating that the quality of the oil is deteriorated, with various metal oxides or other residues, and the safety factor of the operation of the power engineering equipment is relatively reduced.
2.2 Chemical reactions
Transformer oil has some physical properties, in which water-soluble acid, acid value, moisture content, etc. will reflect the working characteristics of transformer oil. Therefore, the main parameters of this physical property will immediately affect the experimental results of transformer oil. For example, acid value reflects the quality of hydraulic oil, and is also a reference for evaluating the embrittlement level of transformer oil. From the specific experimental results, the increase of acid value of transformer oil will increase the level of equipment damage, and finally reduce the dielectric strength of the transformer. In the specific experiment process, the cleanliness of the utensils and their equipment will have a great impact on the measured acid value. For example, water-soluble acid refers to the acid that dissolves water, which is converted into carbonic acid after the reaction between carbon dioxide and water in the air. The resulting carbonic acid will affect 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 there is no water content in the transformer oil and water before the original factory of the transformer, and protective measures must be taken even in the middle and later transportation and storage processes.
2.3 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 of operating oil. The dielectric loss factor of new oil is lower than 0.005. With the improvement of the operating time of the transformer, the transformer oil quality 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 indicates that the oil quality of the transformer has been seriously polluted and deteriorated, and the source of air pollutants should be found out and filtered to solve it 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 moisture content in the oil is too large or the mechanical equipment residue particles in the oil increase, the breakdown field strength will be further reduced, affecting the equipment performance. Safe and smooth operation.
3. Transformer oil spectrum analysis
When the experimental data information is within the standard value range and there is no significant improvement in development, the discriminating machine equipment is operating normally. When the experimental data information exceeds the attention value or improves rapidly, use the three-ratio method, flatulence speed, etc. to conduct in-depth analysis and identification of the current transformer's internal operating conditions. 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 it will accelerate the embrittlement of the transformer oil and affect the dielectric strength. When the oil passage is blocked, the temperature of the transformer part will rise, causing failure; the occurrence of scattered carbon in it will increase the probability of the transformer generating charge and discharge failure; and when the PH is acidic, the electrical conductivity of the transformer oil will increase, The dielectric strength will decrease; in addition, after the open flash point and withstand voltage test of the transformer oil, the electric isolation charge and discharge, operation calorific value, and pressure resistance status of the machinery and equipment can be established. If there is any abnormality, it should be maintained in time.
Good transformer oil should be a clean, transparent liquid with no deposits, suspended solids of mechanical impurities and cotton-like materials. If it is contaminated and oxidized, and produces resin and precipitate, the oil quality of the transformer will deteriorate and the color will gradually turn light red until it turns into a dark brown liquid.
When the transformer is faulty, the color of the oil will also change. Under normal circumstances, when the transformer oil is light brown, it is not suitable for reuse. In addition, the transformer oil can behave as a turbid milky, oily black, and dark. The transformer oil is cloudy and milky, indicating that the oil contains moisture. 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 malfunction inside the transformer.
GTD-61A oil Tan Delta Tester/oil dielectric loss tester/oil dissipation factor and resistivity tester,let you know the performance of the insulation oil.
The test items are required for 110kV/220kV substation acceptance and maintenance testing(with corresponding tester types):
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Test Object |
Testing Item |
Tester Type |
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Cable |
Cable AC Hipot Testing |
JYCX |
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Cable Insulation Resistance Testing |
JYM KYORITSU |
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Transformer |
Insulation Resistance of Winding |
JYM KYORITSU |
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DC Leakage Testing in 1min |
JYDHV |
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Winding Resistance Testing |
JYR50S |
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Winding Deformation Testing |
JYP |
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Turns Ratio Testing |
JYT-A |
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AC Hipot Testing |
JYCX |
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Short Circuit Impedance Testing |
JYW6300 |
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Dan Delta Testing |
JYC |
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Oil Breakdown Voltage (BDV)Testing |
JY6611 |
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Oil Tan Delta Testing |
GTD-61A |
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Switchgear |
Circuit Breaker/Disconnector Resistance |
JYL-200B |
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Relay |
Relay Performance |
JY7003G |
|
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On-load |
On-load Switchgear Testing |
JYK-I |
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Tap Changer Dynamic Testing |
JYK-I |
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Instrument Transformer |
Current Transformer (CT)Testing |
JYH-C |
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Potential Transformer (PT)Testing |
JYH-C |
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Surge Arrestor |
Zinc Oxide Characteristics Testing |
JY6800 |
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1mA DC Reference Voltage |
JYDHV |
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Capacitor |
Capacitor Current |
JY6700 |
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Capacitor Inductance |
JY6700 |
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Ground Grid |
Grounding Down Lead Earth |
JYD |
