To improve the accuracy of fault location system, several short-circuit tests need to be conducted before being brought into service in autotransformer （AT） feeding systems for high-speed railways in China. However,...To improve the accuracy of fault location system, several short-circuit tests need to be conducted before being brought into service in autotransformer （AT） feeding systems for high-speed railways in China. However, no systematic algorithm yet exists to evaluate the consistency of the current distribution of short-circuit tests. A methodology is proposed in this paper to address this problem. Based on Kirchhoff’s current law and the generalized method of symmetrical components, the current deviations of the AT feeding systems are analysed and then normalized with the short-circuit current as they vary greatly with systems and short-circuit sites. It is also found that the short-circuit current varies with the calculation methods, and its unbiased standard deviation also reflects the consistency of the short-circuit test. The mean and maximum of the current deviations, as well as the unbiased standard deviation of the short-circuit current, show the consistency of the short-circuit test from different aspects,although the last two items are highly relevant. Therefore, a unified evaluation index is defined as the sum of the three items, and then applied in two case studies to test its performance. The results show that, the proposed index canclearly distinguish the consistency of the short-circuit tests and may be used to sort the short-circuit tests for fault location systems. Besides, some short-circuit tests may have very poor consistency indices, and thus are not applicable to the tuning of fault location systems. In the authors’ opinion, the determination of the threshold of the proposed index needs further investigation.展开更多
According to the B-H curve and structural dimensions of the snubber by the Fink- Baker Method, the inductive voltage and the eddy current of any core tape with the thickness of the saturated regions are derived when t...According to the B-H curve and structural dimensions of the snubber by the Fink- Baker Method, the inductive voltage and the eddy current of any core tape with the thickness of the saturated regions are derived when the accelerator breakdown occurs. Using the Ampere＇s law, in each core tape, the eddy current of the core lamination is equal to the arc current, and the relation of the thickness of the saturated regions for different laminations can be deduced. The total equivalent resistance of the snubber can be obtained. The transient eddy current model based on the stray capacitance and the equivalent resistance is analyzed, and the solving process is given in detail. The exponential time constant and the arc current are obtained. Then, the maximum width of the lamination and the minimum thickness of the core tape are determined. The experimental time constant of the eddy current obtained, with or without the bias current, is approximately the same as that by the analytical method, which proves the accuracy of the adopted assumptions and the analysis method.展开更多
文摘To improve the accuracy of fault location system, several short-circuit tests need to be conducted before being brought into service in autotransformer （AT） feeding systems for high-speed railways in China. However, no systematic algorithm yet exists to evaluate the consistency of the current distribution of short-circuit tests. A methodology is proposed in this paper to address this problem. Based on Kirchhoff’s current law and the generalized method of symmetrical components, the current deviations of the AT feeding systems are analysed and then normalized with the short-circuit current as they vary greatly with systems and short-circuit sites. It is also found that the short-circuit current varies with the calculation methods, and its unbiased standard deviation also reflects the consistency of the short-circuit test. The mean and maximum of the current deviations, as well as the unbiased standard deviation of the short-circuit current, show the consistency of the short-circuit test from different aspects,although the last two items are highly relevant. Therefore, a unified evaluation index is defined as the sum of the three items, and then applied in two case studies to test its performance. The results show that, the proposed index canclearly distinguish the consistency of the short-circuit tests and may be used to sort the short-circuit tests for fault location systems. Besides, some short-circuit tests may have very poor consistency indices, and thus are not applicable to the tuning of fault location systems. In the authors’ opinion, the determination of the threshold of the proposed index needs further investigation.
基金supported by Research Fund for the Doctoral Program of Higher Education of China (No.20060248012)Shanghai-Canada Research Council cooperation (06SN07113)Auxiliary Heating Project of EAST upgrade, National Program on Key Basic Research Project (973 Program) of China (No.2010GB108003)
文摘According to the B-H curve and structural dimensions of the snubber by the Fink- Baker Method, the inductive voltage and the eddy current of any core tape with the thickness of the saturated regions are derived when the accelerator breakdown occurs. Using the Ampere＇s law, in each core tape, the eddy current of the core lamination is equal to the arc current, and the relation of the thickness of the saturated regions for different laminations can be deduced. The total equivalent resistance of the snubber can be obtained. The transient eddy current model based on the stray capacitance and the equivalent resistance is analyzed, and the solving process is given in detail. The exponential time constant and the arc current are obtained. Then, the maximum width of the lamination and the minimum thickness of the core tape are determined. The experimental time constant of the eddy current obtained, with or without the bias current, is approximately the same as that by the analytical method, which proves the accuracy of the adopted assumptions and the analysis method.
