Abstract
This study investigates the electrical aging characteristics of oil-paper composite insulation. In this paper, a coils model and test system for oil-paper transformer insulation are designed. The electrical aging tests of the model coils at room temperature and operating temperature are performed using the step-stress method. A new method for estimating the unknown parameters in the inverse power exponent model is proposed, and the inverse power model life formula expressed by voltage and electric field strength is obtained. Considering the electrical aging process at the operating temperature, the allowable field strength of the inter-turn insulation of oil-immersed transformers can be improved. The new parameter estimation method proposed in this paper can be used to calculate the unknown parameters of the step-stress solid insulation aging model. This method has a clear physical meaning and can be solved easily. When the stressed voltage is below a certain threshold value, the life of the transformer coil turn-to-turn insulation grease oiled paper model is longer at operating temperatures compared with that at room temperature; when the voltage is higher than the threshold, it presents the opposite tendency.
Highlights
As the core component of power systems, failure of a power transformer results in direct or indirect economic losses, which directly affect the security of the power grid [1,2,3]
When the voltage is greater than the threshold value, the partial discharge (PD) intensity at operating temperature is greater than that at room temperature
ItItisisseen that when thethe stressed voltage is below a certain threshold value,value, the lifethe of life of the transformer coil turn-to-turn insulation grease oiled paper model is longer at operating the transformer coil turn-to-turn insulation grease oiled paper model is longer at operating temperatures
Summary
As the core component of power systems, failure of a power transformer results in direct or indirect economic losses, which directly affect the security of the power grid [1,2,3]. The aging of oil-immersed paper insulation is influenced by the electric field, temperature, moisture, oxygen, and other factors [6,7,8,9]. Among these factors, the damage caused by electrical aging cannot be ignored [10,11]. Understanding the electrical aging properties of oil-immersed paper insulation under various temperatures, evaluating the insulation properties of a power transformer late in its life, and adopting a flexible life cycle greatly improves the economy and reliability of a power grid operation [12,13]
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