CN-121983193-A - Modeling method for flow injection discharge process in natural ester insulating oil by considering ionization in bubbles

Abstract

The invention discloses a modeling method for a natural ester insulating oil streamer discharge process considering ionization in bubbles, which comprises the steps of 1) constructing a two-dimensional non-axisymmetric model for simulating streamer discharge of bubbles in the natural ester insulating oil under lightning impulse voltage, 2) introducing plasma chemical reaction, constructing a natural ester insulating oil streamer discharge electrohydrodynamic model for coupling the ionization process of gas molecules in the bubbles, and simulating a natural ester insulating oil streamer morphology evolution process by the natural ester insulating oil streamer discharge electrohydrodynamic model after applying set voltage to the two-dimensional non-axisymmetric model. According to the invention, the drift-diffusion-reaction process of plasmas in bubbles and a poisson equation are self-consistent solved, and the plasma generation process in the bubbles under a strong electric field is integrated into the existing streamer discharge model, so that the understanding of a liquid dielectric breakdown theory is facilitated.

Inventors

• LI JIAN
• ZENG NINGYU
• HUANG ZHENGYONG
• LI CHANGHENG
• WANG FEIPENG
• CHEN WEIGEN

Assignees

• 重庆大学

Dates

Publication Date

20260505

Application Date

20251225

Claims (10)

1. 1. A modeling method for a current injection discharge process in natural ester insulating oil considering ionization in bubbles is characterized by comprising the following steps: Step 1), constructing a two-dimensional non-axisymmetric model for simulating the flow injection discharge of bubbles in natural ester insulating oil under lightning impulse voltage; And 2) introducing plasma chemical reaction to construct a natural ester insulating oil streamer discharge electrohydrodynamic model for coupling the ionization process of gas molecules in bubbles.
2. 2. The modeling method for the natural ester insulating oil streamer discharge process taking into account the ionization in the bubbles according to claim 1, wherein the natural ester insulating oil streamer discharge electrohydrodynamic model simulates the natural ester insulating oil streamer morphology evolution process after a set voltage is applied to a two-dimensional non-axisymmetric model.
3. 3. The modeling method for the streamer discharge process in the natural ester insulating oil considering the ionization in the bubbles according to claim 2, wherein the bubbles in the natural ester insulating oil are generated in a random simulation mode when simulating the streamer morphology evolution process of the natural ester insulating oil.
4. 4. The modeling method of a natural ester insulating oil in-flow discharge process considering ionization in bubbles according to claim 1, wherein the two-dimensional non-axisymmetric model comprises a liquid phase region, a gas phase region and a simulation electrode.
5. 5. The modeling method of the streamer discharge process in a natural ester insulating oil taking into account ionization in bubbles according to claim 1, wherein the liquid phase region is a region simulating the natural ester insulating oil.
6. 6. The modeling method of a streamer discharge process in a natural ester insulating oil, taking into account ionization within bubbles, according to claim 1, wherein the gas phase region is a region simulating plasma.
7. 7. A method of modeling a streamer discharge process in a natural ester insulating oil, in which ionization within the bubbles is considered as claimed in claim 1, wherein the discharge electrode extends from a gas phase region into a liquid phase region.
8. 8. The modeling method of the natural ester insulating oil streamer discharge process taking into account ionization in bubbles according to claim 1, wherein the natural ester insulating oil streamer discharge electrohydrodynamic model is as follows: (1) (2) (3) (4) (5) In the formula, 、 Carriers generated for field ionization and impact ionization; Is the electric field strength; 、 、 、 、 、 、 、 、 、 、 、 、 、 、 、 、 、 The insulating oil is prepared from insulating oil, dielectric constant, vacuum dielectric constant, positive ion charge density, negative ion charge density, electron charge density, positive ion mobility, charged particle generation source item, H function, positive ion and negative ion recombination rate, positive ion and electron recombination rate, electron charge, electron adsorption time, temperature, heat conduction time, insulating oil density, specific heat capacity, current density and flow rate.
9. 9. The modeling method of the streamer discharge process in natural ester insulating oil considering ionization in bubbles according to claim 8, wherein carriers generated by field ionization are as follows: (6) In the formula, 、 、 、 、 Is the molecular number density, molecular spacing, effective electron mass, ionization energy, and Planck constant.
10. 10. The modeling method of the streamer discharge process in natural ester insulating oil taking into account ionization in bubbles according to claim 8, wherein carriers generated by impact ionization are as follows: (7) In the formula, 、 、 The index term coefficient is the index coefficient before the index coefficient.

Description

Modeling method for flow injection discharge process in natural ester insulating oil by considering ionization in bubbles Technical Field The invention relates to the field of electrical breakdown, in particular to a modeling method for a streamer discharge process in natural ester insulating oil by considering ionization in bubbles. Background In recent years, the electrical breakdown characteristics of insulating liquids are becoming research hot spots, and the application fields of the insulating liquids include the fields of insulating oil synthesis, reliability evaluation of electric equipment, environmental repair and the like. However, the nature of electrical breakdown of dielectric liquids (especially natural esters) remains controversial despite extensive research. In general, streamer development in liquids is extremely sensitive to the waveform of the applied voltage, polarity, electrode geometry, and gap distance. However, most of the above studies are based on pure dielectrics, and such ideal conditions are difficult to achieve in practical engineering scenarios. The natural ester insulating oil is used as a dielectric liquid, has good environmental protection performance, and the insulating performance is comparable with mineral oil, so that the natural ester insulating oil is widely applied to high-voltage power equipment. There have been many studies showing that bubbles, fibers, metal particles and other impurities may be generated in the transformer under the action of thermal stress or local electric field, and these impurities may increase the breakdown probability of insulating oil. The generation of bubbles in the transformer oil is various in reasons, and the bubbles can be caused by enthalpy change in the discharging process, and can also be caused by factors such as mechanical vibration, insufficient vacuum oiling, ageing of sealing elements and the like. Under atmospheric pressure conditions, the dielectric constant of natural esters is about 3 times that of bubbles, which can lead to distortion of the electric field inside the bubbles, resulting in a breakdown field strength of the pure liquid that is much higher than that of the bubble-containing liquid. The presence of bubbles in dielectric fluids increases the probability of breakdown, and thus there has been much research focused on this phenomenon. These studies have involved parameters such as gas composition within the bubbles, dielectric constants or conductivities of liquids and gases, bubble geometry, electrode placement and power supply type, etc. But there is still a lack of numerical research on how gas molecular ionization inside the bubble affects streamer propagation. Disclosure of Invention The invention aims to provide a modeling method for a streamer discharge process in natural ester insulating oil, which considers ionization in bubbles, and comprises the following steps: Step 1), constructing a two-dimensional non-axisymmetric model for simulating the flow injection discharge of bubbles in natural ester insulating oil under lightning impulse voltage; Step 2) introducing plasma chemical reaction to construct a natural ester insulating oil streamer discharge electrohydrodynamic model for coupling the ionization process of gas molecules in bubbles; further, after a set voltage is applied to the two-dimensional non-axisymmetric model, the natural ester insulating oil streamer discharge electrofluid dynamics model simulates the evolution process of the natural ester insulating oil streamer morphology. Further, when simulating the appearance evolution process of the natural ester insulating oil streamer, bubbles in the natural ester insulating oil are generated in a random simulation mode. Further, the two-dimensional non-axisymmetric model includes a liquid phase region, a gas phase region, and a simulated electrode. Further, the liquid phase region is a region simulating a natural ester insulating oil. Further, the gas phase region is a region simulating plasma. Further, the discharge electrode extends from the gas phase region into the liquid phase region. Further, the natural ester insulating oil streamer discharge electrohydrodynamic model is as follows: (1) (2) (3) (4) (5) In the formula, 、Carriers generated for field ionization and impact ionization; Is the electric field strength; 、、、、、、、、、、、、、、、、、 The insulating oil is prepared from insulating oil, dielectric constant, vacuum dielectric constant, positive ion charge density, negative ion charge density, electron charge density, positive ion mobility, charged particle generation source item, H function, positive ion and negative ion recombination rate, positive ion and electron recombination rate, electron charge, electron adsorption time, temperature, heat conduction time, insulating oil density, specific heat capacity, current density and flow rate. Further, carriers generated by field ionization are as follows: (6) Further, carriers generated by impact i