Method of evaluating working condition of insulating oil of power transformer

Abstract

The invention discloses a method of evaluating the working condition of insulating oil of a power transformer. The method is characterized in that a mathematical relationship between temperature parameters and dielectric loss factors is established by measuring corresponding dielectric loss factors tgdelta of the insulating oil at two temperature points of 70 DEG C and 90 DEG C, as well as the equally spaced temperature points from 70 DEG C to 70-90 DEG C, so that a coefficient of the mathematical relationship is obtained; the coefficient can reflect a linear trend corresponding to the mathematical relationship to the maximum extent; and then the numerical range of the coefficient is analyzed to evaluate the working condition of the existing insulating oil. According to the method, the working condition of the insulating oil of the transformer can be known in advance, so that abnormalities of the insulating oil can be found in advance for tracing and detecting with pertinence, and thus, hidden dangers can be eliminated as early as possible to achieve safety in use. Furthermore, the method is simple and convenient to operate, fully and specific, high in accuracy and high in degree of intelligentization, and provides a reliable scientific basis for normal operation and maintenance of transformer equipment.

Description

technical field [0001] The invention relates to the field of detection of power transformer insulating oil, in particular to a method for evaluating the working state (normal state, abnormal state, attention state) of power transformer oil in operation. Background technique [0002] The main functions of insulating oil for power transformers are insulation, arc extinguishing, heat dissipation and carrier information transmission. The quality of transformer insulating oil is a necessary condition to ensure the safe operation of power transformers. [0003] Under the action of an electric field (after voltage is applied), the dielectric will undergo a polarization process and a conduction process. There is energy loss in the process of lossy polarization; in the process of conduction, there is of course energy loss in the conduction leakage current flowing through the insulation resistance. The degree of loss is generally expressed by the energy lost per unit time, that is, ...

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Problems solved by technology

However, this method has two main limitations: first, it only detects the dielectric loss factor of transformer oil at 90°C, and the dielectric loss factor changes dynamically and increases with the increase of temperature. It is very limited, and its change trend with temperature rise cannot be observed, so it is impossible to predict in advance and clearly distinguish whether the transformer is good or bad; second, it does not take into account the uncertainty of the influence of a small amount of polar substances on the dielectric loss of oil

In addition, glassware has an adsorption effect on oil. Using glassware to hold oil samples and storing oil samples for too long will seriously affect the accuracy of measurement.

Polyethylene plastic bottles should be used to take samples away from light, and the test should be carried out on the day of sampling, which is limited by time and inconvenient to operate

[0006] In addition, the biggest shortcoming of the existing technology is that the working state of the transformer insulating oil cannot be predicted in advance

The deficiencies of the above-mentioned existing methods can be briefly summarized as the following two aspects: On the one hand, this method of testing at the specified time regardless of the state of the transformer insulating oil often cannot achieve "inspection when it is detected", and it is targeted

On the other hand, for the transformer insulating oil that has serious defects or faults and really needs maintenance, the problem cannot be found and dealt with in time because the inspection period has not arrived, so that the defective transformers continue to develop and lead to accidents, endangering the safe operation of the power grid

[0007] Therefore, the existing method of planned detection cannot predict in advance which transformer's insulating oil may be abnormal in the future under the power-on state, so that targeted, tracking detection and evaluation cannot be realized, which affects the detection of transformers that may be abnormal. Preventing oil in advance and maintaining it in time also affects the overall operating efficiency of the transformer, resulting in a waste of manpower and material resources

[0008] In short, the current detection methods for transformer insulating oil are inconvenient to operate, have limitations, poor accuracy, and low intelligence.

And it is impossible to predict the working state of transformer insulating oil in advance

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