Power transformers play an important role in power system. In recent years, with the rapid development of UHV power grid, transformer explosions occurred occasionally, often followed by fires, which caused serious economic loss and casualty. For disaster mitigation of transformer explosion, a balance design concept for power transformer against arc fault explosion was proposed, which includes vulnerability analysis of transformer structure, optimization design, and pressure-relief design scheme. For realizing the balance design, nonlinear dynamic finite element analysis of an 800kV converter transformer considering possible arc failure occurrence and fluid-structure interaction was carried out based on LS-DYNA. The transformer model included tank, ascending flange stiffening rib and winding. The method used to achieve gas production successfully simulates high pressure gas loading. Propagation of pressure wave, pressure distribution on transformer structure, and dynamic response characteristic of the transformer were observed in different typical arc fault occurrence. Weak points of the structure were identified and corresponding design measures about stiffening rib and stress concentration location are proposed to reach optimal design. The design and arrangement of the pressure-relief device for typical arc fault occurrence were suggested. A pressure relief device was set on ascending flange which closed to arc fault. Its quick trigger changed the response characteristic of structure and decreases the peak stress. The efficacy of the proposed design concept was validated through numerical analysis. The research findings from this paper provide reference for improving explosion resilience design of transformer.
This paper processes simulate analysis of short-circuit test model of transformer,using finite element analysis software ANSYS.The winding and disk deformation is calculated in different elastic modulus value of strip;By changing the size of strip circumferential direction,radial displacement of disk is calculated corresponding to the four strip size;The model is calculated and analyzed in the load of short-circuit test,the maximum deformation 2.62 mm of disk obtained is consistent with actual measured value 2.906 mm.This analysis method in paper can be used for large power transformer winding short-circuit strength and radial stability analysis.
The service life of porous concrete (PC) structures is severely affected by freeze–thaw damage in cold regions. However, the evaluation of freeze–thaw damage of PC using experimental tests is time-consuming and inconvenient. This paper derived an equation to evaluate the freeze–thaw damage and developed a model to predict the residual strength of PC under freeze–thaw conditions based on the Weibull distribution functions. By analyzing the experimental results, the relative dynamic elastic modulus (RDME) was identified as the damage variable, which can accurately characterize the freeze–thaw damage state of PC with the advantages of convenience and nondestructiveness. Moreover, the resistance to freeze–thaw cycles of the PC blended with basalt fibers and silica fume increased by 25% compared with that without any reinforcement. Based on the damage accumulation theory, the Weibull distribution function is appropriate to be employed to describe the freeze–thaw damage evolution of PC. The model for predicting the residual strength of PC subjected to freeze–thaw cycles was verified based on a large amount of test data and had correlation coefficients R2 higher than 0.96. The proposed model also can be used to predict the residual strength of other types of PC, and provides a reference for service life prediction and safety assessment of PC structures.
Power transformer is the key equipment in the power system. In recent years, transformer explosion occurred frequently, most of which caused fire and resulted in heavy losses. Research in this field is still in the initial stage. To analyze the anti-explosion performance of transformers, an equivalent load model for transformer arc fault is firstly proposed in this paper, and the relevant numerical simulation is carried out. Fluid-structure interaction is considered in the numerical simulation, and finally the load distribution field and the structural response characteristics of the transformer are obtained for two typical arc fault locations.
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