Writer： Kaiqian Oil Purifier Release time：2021-06-10 19:01 Clicks：
Breakdown voltage is also an index for evaluating the electrical performance of transformer oil. It can be used to determine the degree of contamination of insulating oil with water and other suspended solids, as well as to inspect the drying of the oil before it is injected into the equipment and the performance of the transformer oil filter.
When a gradually increasing voltage is applied to the clean and dry oil, shooting electrons will be emitted at the negative terminal of the voltage. When the electrons have sufficient energy, the oil molecules can be micro-dissociated, so the entire dissociation process is strengthened as the voltage increases. When a certain voltage is reached, a large amount of conduction current will be generated to form an arc. This phenomenon is called breakdown, and the voltage during breakdown is called breakdown voltage. If there is water or solids in the oil, the breakdown voltage will be reduced. At this time, the conductivity of water and solids is greater than that of oil. The low breakdown voltage of the oil during operation is a signal of the dangerous work of the transformer.
For transformer oil domestic and foreign standards, the breakdown voltage is generally 40~50KV, and the high is 60-80KV or even more.
2.The Factors affecting breakdown voltage of transformer oil
The reason why the breakdown voltage of the insulating oil of the transformer is invalid: the quality of the insulating oil changes badly, the moisture is too high, damp and cold, too much impurities, and the temperature changes. The key function of insulating oil is refrigeration and insulation. It also has the function of removing arcs caused when the power circuit is disconnected. Affect the breakdown voltage of transformer oil.
The electrolytic medium will lose its dielectric performance as an electrical conductor under the effect of a sufficiently strong electrostatic field, which is called dielectric breakdown, and the relative working voltage is called breakdown voltage. The field strength of the dielectric breakdown is called the breakdown field strength. Different substances have different breakdown field strengths at the same temperature. When the distance between the capacitor material and the bipolar plate is clear, the breakdown voltage is determined by U1-U2=ED.
The factors that affect the compressive strength of transformer oil insulation are relatively largeThe main transformer is sealed or oleophobic (with a moisture absorber). The oil and water of the transformer are affected by the natural environment. The oil and water (referring to the micro-water content) of the transformer shall be regulated by the rated voltage of the transformer, 115kV≤20ppm, 225kV, 15ppm, 500kV≤10ppm.
After the oil is dissolved, the high-temperature arc will cause carbonization and cracking of the oil, resulting in various impurities, such as carbon deposits, grease stains, water, hydrogen, acetylene gas, methane gas, etc. The melting or floating of such hazardous components in the oil will significantly reduce the insulating layer of the oil. Therefore, the more frequent the penetration, if the oil filtration is not carried out immediately, the breakdown voltage will drop sharply.
3. The Methods to deal with transformer oil and prevention
1) Filtering: You can use an transformer oil purification machine for filtering. Principle: When the oil filter is working, the oil enters the primary filter through the inlet under the action of the internal and external pressure difference, and the large particles are filtered out. After the oil is heated by multi-stage infrared rays, it enters the special personalized vacuum separator. The vacuum separator first forms a mist shape and then a film shape, which enlarges the contact area in vacuum hundreds of times. The moisture in the oil is under the conditions of high heat, high vacuum, large surface, and high pumping speed. Get quickly vaporized and discharged by the vacuum system.
The water vapor discharged from the upper part of the vacuum separator is first cooled and dehumidified by the condenser, and then enters the cooler to cool again. The condensed water enters the water reservoir and is discharged. After the gas is condensed and dehumidified twice, it is finally discharged into the air by the vacuum pump.
The dry oil in the vacuum separator after vacuum vaporization and dehydration is raised from negative pressure to positive pressure by the oil transfer pump. After filtration, the net oil is discharged from the oil outlet to complete the entire net oil process.
2) Waterproof: heat insulation must be dried before the oil changes, and some further use vacuum pump extraction to remove water. In the whole process of equipment manufacturing, avoid re-moisture and impurity intrusion. It is made as a barrier to the air. When the liquid insulation layer in some commodities is not completely protected from the air, a moisture absorber containing moisture-proofing agent should be used at the air inlet to avoid direct contact between water and oil level.
3) Degassing: The common way of degassing is to heat the oil, paint it into a mist, and vacuum package to remove the moisture and vapor in it; in the case of an oil vacuum pump, it enters the body and the electric device.
4) Application of oil and solid substances, such as covering, insulating layer, natural barrier, etc.
Anti-fouling: The production workshops that produce insulating layer components, windings and products with special requirements must have anti-fouling countermeasures, so that after the product drips, dust is not allowed to invade, and the dielectric strength of the oil is reduced.
4.The Oil samples purified Before and After.
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