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Abstract: This paper proposes an innovative structural wall, named “the steel tube–double steel plate–concrete composite wall”, which is suited for use in high-rise buildings. The composite wall consists of concrete filled steel tubular (CFST) boundary elements and a double “skin” composite wall web where two steel plates are connected by tie bolts with space between them filled with concrete. The seismic behavior of the composite walls was examined through a series of experiments in which five slender rectangular wall specimens were subjected to axial forces and lateral cyclic loading. The specimens failed in a flexural mode, characterized by local buckling of the steel tubes and plates, fracture of the steel tubes, and concrete crushing at the wall base. The extent of the CFST boundary element was found to significantly affect the deformation and energy dissipation capacities of the walls. The area ratio of steel plates had a minimal effect on the deformation capacity of the slender walls. The addition of circular steel tubes embedded in the CFST boundary elements obviously increased the lateral load-carrying capacity of the walls. When the CFST boundary element's extent was 0.2 times the wall's sectional depth and the test axial force ratio was no more than 0.25, the walls had a yield drift ratio of over 0.005 and an ultimate drift ratio of around 0.03. Simplified formulas used to evaluate the flexure strength of the composite walls were proposed. The evaluated results had good agreement with the test results, with errors no greater than 10%. [Copyright &y& Elsevier]

Eddy-current analysis and losses estimation are significant components in the optimized design of the tractive transformer. The conventional analytical method forces to linearize the nonlinear magnetic property and as an important quantity in the calculation, the permeability is only acquired dependent on the empirical method. Furthermore, the computational precision is often difficult to assure in losses estimation when distorted excitation originated from nonlinear magnetized relation in electrical steel is neglected. In our study, the eddy-current field problem is delicately solved by analytical deduction, in which the nonlinear constitutive relation toward media and the harmonic component in the excitation source are sufficiently considered. Compared with the accuracy of the traditional formula, the proposed model achieves better accuracy on eddy-current losses with finite-element analysis, especially when the operating condition is closed to magnetic saturation. [ABSTRACT FROM AUTHOR]

A new testing method (oscillating wave method) has been proposed as a solution to the problem of short maintenance time in the traction power supply system, which could complete tests of winding and insulation via one connection and improve the maintenance efficiency of the transformer. Through the method being proved highly sensitive to winding faults, the variation under different winding states, however, remains unclear. This article aims to analyze oscillating wave signatures in the occurrence of axial displacement (AD). First, the modeling method will be proposed that can simulate oscillating wave signatures in different winding states. Then, the time-domain feature and the new proposed frequency-domain feature are applied to analyze the fault extent and location of AD fault. The results show that this model accurately simulates oscillating wave signatures. Moreover, the time-domain feature [Euclidean distance (ED)] is closely related to fault extent. The combined use of the time-domain feature (ED) and the frequency-domain feature (W-Energy entropy in Z-Score) is effective in the identification of fault location. These features, therefore, can provide the reference for winding state evaluation. [ABSTRACT FROM AUTHOR]

In this article, a new testing method for the diagnosis of winding faults based on the resonant frequency of the transformer is proposed. The system that consists of the high-voltage dc power and high-voltage insulated gate bipolar transistor (IGBT) could charge the transformer periodically. The response measured from the bushing of the winding is the oscillating wave that can be used for evaluating the status. Carrying out the new test on a 220-kV three-winding, three-phase transformer in the field, the tests of insulation and the winding have been completed in one test. The calculated frequency verifies the feasibility and applicability of the method in theory and the voltage does not affect the resonant frequency in the test. The three-winding, three-phase model transformer was built to simulate the various parameters of the power supply, which proves that the features of the oscillating waves are brought about by the properties of the transformer. Also, the new testing method provides a new opportunity to do parameter identification of axial displacement and short-circuit (SC) fault. The abovementioned research shows that the proposed method can conduct the test of winding and insulation in one test for a short time, which proves a reference in the field. [ABSTRACT FROM AUTHOR]