CN-116050214-B - Oilpaper insulation partial discharge simulation method under cuprous sulfide deposition

CN116050214BCN 116050214 BCN116050214 BCN 116050214BCN-116050214-B

Abstract

The invention belongs to the technical field of transformer oil sulfur corrosion protection, and relates to an oil paper insulation partial discharge simulation method under cuprous sulfide deposition, wherein a finite element simulation software COMSOL Multiphysics is used for establishing a geometric model of the oil paper insulation partial discharge and designing a cuprous sulfide deposition point; setting a physical field and boundary conditions based on a geometric model, establishing a transformer oil fluid dynamic model and an insulated paper bipolar charge carrier transmission model, carrying out grid division on the model, setting initial parameters, solver parameters and voltage excitation, carrying out transient calculation on the model, and solving the electric field distribution and charge distribution conditions in the partial discharge process of the model. According to the invention, the intensity of partial discharge when the cuprous sulfide is deposited at different positions of the oil paper insulation is predicted and calculated by utilizing the fluid dynamics model and the bipolar charge carrier model, and a reference is provided for the influence of the cuprous sulfide deposition on the partial discharge characteristic in the oil-immersed transformer, so that the safety accidents caused by the insulation degradation of the transformer due to the cuprous sulfide deposition are reduced.

Inventors

CONG HAOXI
Qiao Lipan
WANG YUXUAN
Gao Erkang
LI QINGMIN

Assignees

华北电力大学

Dates

Publication Date: 20260508
Application Date: 20230109

Claims (3)

1. The method for simulating the partial discharge of the oilpaper insulation under the deposition of cuprous sulfide is characterized by comprising the following steps of: step S1, establishing an oilpaper insulation partial discharge geometric model based on finite element simulation software, and setting cuprous sulfide deposition points; The oil paper insulation partial discharge geometric model is needle plate discharge, wherein insulation paper is placed on the surface of a plate electrode, transformer oil is filled in a cavity, and cuprous sulfide deposition is arranged on the surface of the insulation paper, in the insulation paper and in a pit; step S2, setting materials, physical fields and boundary conditions based on a geometric model, and describing charge transmission processes of insulating oil and insulating paper by using a fluid dynamics model and a bipolar charge carrier transmission model respectively; the boundary condition of the combination of the two models adopts an ohmic model to describe the charge transmission process between the oil paper interfaces, and the relationship is shown in the formula (1); (1) Wherein ρ s is the interfacial charge density, μ 0 is the charge mobility in oil, Is paper conductivity; boundary conditions between cuprous sulfide deposition and transformer oil are shown in the formula (2) and the formula (3); (2) (3) Wherein: to be the charge density of the interface between cuprous sulfide and transformer oil, And The longitudinal and transverse electric field intensities of the cuprous sulfide surface are respectively, And The longitudinal electric field intensity and the transverse electric field intensity of the surface of the transformer oil are respectively; Step S3, carrying out grid division on the model, and setting initial parameters, solver parameters and voltage excitation; the grid encryption is carried out on the needle tip discharge area when the grid is split, the grid of the external area is sparse, and the voltage excitation is simulated lightning impulse voltage; And S4, performing transient calculation on the model, and solving the electric field distribution and charge distribution conditions in the partial discharge process of the model.
2. A method for simulating partial discharge of an oilpaper insulation under copper sulfide deposition according to claim 1, wherein said model of oil fluid dynamics in step S2 comprises: Describing the generation, migration and dissipation of electrons and positive and negative ions in the oil by adopting a current continuity equation and a poisson equation, and describing the temperature change in the oil by adopting a heat conduction equation, wherein the relation is shown in formulas (4) to (8); (4) (5) (6) (7) (8) Wherein ρ p 、ρ n and ρ e are the charge densities of positive ions, negative ions and electrons in transformer oil, G I 、G D and G T are the charge density change rates caused by oil field ionization, ion pair dissociation in oil and impact ionization in oil, R pe and R pn are the recombination rates of positive ions and electrons and positive ions and negative ions, Τ a is the electric field strength, μ p 、μ n and μ e are the mobility of positive ions, negative ions and electrons, respectively, q is the electron charge amount, ε 0 is the vacuum dielectric constant, ε r is the oil phase permittivity, ρ l is the oil mass density, c v is the oil specific heat capacity, and k T is the oil thermal conductivity.
3. The method for simulating partial discharge of oilpaper insulation under copper sulfide deposition according to claim 1, wherein the bipolar charge carrier transport model in step S2 comprises: Calculating charge densities of various charge carriers by using a continuity equation and a poisson equation of four types of particles, namely free electrons, trapped electrons, free holes and trapped holes: (9) (10) (11) (12) (13) Wherein: 、、 And The charge densities of free electrons, free holes, trapped electrons and trapped holes in the insulating paper, And The mobility of free electrons and free holes respectively, 、、 And The recombination rate of the trapped holes and the trapped electrons, the recombination rate of free electrons of the trapped holes, the recombination rate of the free holes and the recombination rate of free electrons and free holes are respectively, 、、 And Respectively an electron trapping rate, a hole trapping rate, an electron detrapping rate and a hole detrapping rate, And For the electron maximum trap density and the hole maximum trap density, ε 0 is the vacuum dielectric constant and ε r is the dielectric constant of the insulating paper.

Description

Oilpaper insulation partial discharge simulation method under cuprous sulfide deposition Technical Field The invention relates to an oilpaper insulation partial discharge simulation method under cuprous sulfide deposition. Background The oil immersed transformer is used as the most commonly used transformer in power transmission and distribution equipment, a large amount of mineral insulating oil is filled in the transformer, the aging of the insulating oil has a great threat to the safe and stable operation of the transformer, trace impurities exist in the insulating oil of the transformer, corrosive sulfur is one of the trace impurities, and the corrosive sulfur can corrode copper in the transformer, so that the oil paper insulation faces sulfur corrosion fault threat. According to research, the candelabra sulfur in the transformer oil reacts with the copper conductor to generate cuprous sulfide deposition, and the deposition causes the reduction of the insulation performance of the transformer oil paper, which is suspected to be the cause of a plurality of transformer accidents at home and abroad, in particular to the cause of converter transformer accidents. Partial discharge is very easy to occur under the combined action of factors such as electricity, heat, mechanical force and the like in the oil paper insulation, so that the insulation performance is reduced and even power failure is caused. Copper sulphide deposits produced under the action of corrosive sulphur have been shown to exacerbate the generation of partial discharges, leading to further deterioration of insulation, which is detrimental to the long-term stable operation of the transformer. The research is mainly aimed at the partial discharge characteristics of the oil paper insulation under different electric field environments, and the related research of the influence of cuprous sulfide deposition on the partial discharge characteristics of the oil paper insulation is lacked. The cuprous sulfide deposit has extremely strong dispersibility, randomness and obvious polarity effect, is easy to trigger partial discharge and has great harm to insulation. The cuprous sulfide deposition is taken as a factor influencing partial discharge, and the influence of the cuprous sulfide deposition on the space charge characteristics of the insulating oilpaper is to be further researched, and particularly the effects of the space charge characteristics and the space electric field distribution on different deposition positions, deposition amount and penetration degree of the cuprous sulfide are also required to be researched. The invention simulates partial discharge conditions of cuprous sulfide deposition at different positions from transient state by utilizing COMSOL simulation, and can obtain space charge density, electric field intensity distribution, temperature distribution and the like in the partial discharge process. Has important significance for sulfur corrosion research in oil immersed transformers and reducing the probability of transformer accidents. Disclosure of Invention The invention aims to provide an oil paper insulation partial discharge simulation method under cuprous sulfide deposition, which is used for simulating and calculating key data such as oil paper insulation space charge distribution, electric field intensity distribution and the like under transient conditions by simulating and simulating the oil paper insulation partial discharge process under cuprous sulfide deposition. The simulation model provides a reference for the influence of cuprous sulfide of the oil immersed transformer serving in the power grid system on the partial discharge characteristic, so that safety accidents caused by insulation degradation of the transformer due to cuprous sulfide deposition are reduced. In order to achieve the purpose, the invention adopts the following technical scheme that the method for simulating the partial discharge of the oilpaper insulation under the deposition of cuprous sulfide comprises the following steps: step one, establishing an oilpaper insulation partial discharge geometric model based on finite element simulation software COMSOL Multiphysics, and setting cuprous sulfide deposition points; Setting materials, a physical field and boundary conditions based on a geometric model, describing charge transmission processes of insulating oil and insulating paper by using a fluid dynamics model and a bipolar charge carrier transmission model, and describing charge transmission characteristics of an oil paper interface and an oil and cuprous sulfide deposition interface by using an ohmic model; Step three, carrying out grid division on the model, and setting initial parameters, solver parameters and voltage excitation; Step four, performing transient calculation on the model, and solving the electric field distribution and charge distribution conditions in the partial discharge process of the model; The oil paper insulation