The oil in the oil-immersed transformer plays an important role in insulation, cooling and arc extinguishing. The quality of the oil directly affects the normal operation and service life of the transformer. To determine whether the oil needs to be replaced, multiple factors need to be considered comprehensively.
First, a preliminary judgment can be made by appearance and color. Normal transformer oil should be a transparent, slightly yellow liquid. If the color of the oil becomes darker, brown or even black, or turbidity, precipitation and suspended matter appear in the oil, this usually indicates that the oil quality has deteriorated and may need to be replaced.
Secondly, the oil breakdown voltage test is carried out. The breakdown voltage is an important indicator for measuring the insulation performance of the oil. Using professional testing equipment, if the breakdown voltage is lower than the specified minimum value, it means that the insulation performance of the oil has decreased and the safe operation of the transformer cannot be effectively guaranteed. At this time, the oil may need to be replaced.
The moisture content in the oil is also a key factor. Moisture will reduce the insulation performance of the oil and accelerate the aging of the oil. Through the moisture meter, if the moisture content exceeds the allowable standard, it is necessary to consider replacing the oil.
The acid value is also an important parameter for judging the oil quality. The oil will undergo oxidation reaction during use to produce acidic substances. Too high an acid value will corrode the metal parts inside the transformer, and it also indicates that the oil quality has deteriorated.
In addition, the dissolved gas content in the oil can also be detected. When the transformer fails internally, some specific gases will be produced and dissolved in the oil. Through gas chromatography analysis, if the gas content is found to be abnormal, such as excessive gas content such as hydrogen and acetylene, in addition to checking whether the transformer is faulty, it may also mean that the oil quality has been affected and needs to be replaced.
In addition, the flash point and viscosity of the oil are also reference indicators. A decrease in the flash point may mean an increase in light components in the oil, which poses a safety hazard; an increase in viscosity will affect the fluidity and heat dissipation of the oil.
In actual operation, the oil of the oil-immersed transformer should be sampled and tested regularly. For transformers with harsh operating environments, heavy loads or long service life, the frequency of detection should be increased.
For example, if an oil-immersed transformer operating in a high temperature and high humidity environment has not been tested and maintained for a long time, the moisture and impurities in the oil may gradually increase, resulting in a decrease in insulation performance and causing short circuits and other faults.
In summary, judging whether the oil quality of the oil-immersed transformer needs to be replaced requires the comprehensive use of multiple detection methods and indicators, combined with the operating conditions and environmental conditions of the transformer for a comprehensive assessment to ensure the safe and stable operation of the transformer.
