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The DC magnetic bias phenomenon in transformers can result in increased noise and harmonic components. This study focuses on the DC magnetic bias generated by stray currents in the DC traction power supply system of neutral grounding transformers under multiple train operation conditions. A two-layer soil model is utilized to calculate geodetic potential, with rail potentials from both mainline and depot serving as sources for stray current within the model. Two paths of stray current intrusion into the transformer via the grounding network and cable armor layer from the Main substation have been modeled and analyzed. A simulation test has been designed to verify that the maximum error between experimental data and model calculation data is 8.87%. The implementation of a blocking connection device between the depot and mainline, as well as a change in grounding strategy for the metal protective layer, can effectively reduce DC bias magnetic current in the substation.

• By utilizing Green's formula, the earth potential under multi-train operating conditions is calculated. • Two stray current intrusion paths from the substation grid and armored cable are considered. • The main intrusion path of stray current is the metal protection layer of the armored cable. • Change the grounding strategy of the metal protection layer and use BCD to control DCBMC. The DC magnetic bias phenomenon in transformers can result in increased noise and harmonic components. This study focuses on the DC magnetic bias generated by stray currents in the DC traction power supply system of neutral grounding transformers under multiple train operation conditions. A two-layer soil model is utilized to calculate geodetic potential, with rail potentials from both mainline and depot serving as sources for stray current within the model. Two paths of stray current intrusion into the transformer via the grounding network and cable armor layer from the Main substation have been modeled and analyzed. A simulation test has been designed to verify that the maximum error between experimental data and model calculation data is 8.87%. The implementation of a blocking connection device between the depot and mainline, as well as a change in grounding strategy for the metal protective layer, can effectively reduce DC bias magnetic current in the substation. [ABSTRACT FROM AUTHOR]

Transformer is an important equipment for power energy transmission. The vibration and noise of transformer have always been a serious issue of people concern. Transformer body vibration and noise are mainly caused by the global magnetization of limbs and yokes and magnetic forces of transformer core. However, the process of vibration transfer from core to body is a key factor for monitoring the transformer condition. In this paper, a transformer model for vibration transmission is presented based on motion transmission and it can be used to analyze the vibration relation between core and shell of transformer. Considering strain of silicon steel as the vibration source, the motion equations whichexpress the relations of transformer core and shell are derived. And then, the test system is built to analyze the vibrations of a 5 kVA three phase transformer. A 3D real model simulation used COMSOL finite element software is performed for analyzing the deformation characteristic of transformer. The locations of test points which reflect the vibration more efficiently are determined through the deformation simulation results. Lastly, the vibration signals of two directions have been measured considering DC magnetic bias or not. The experimental results reveal that vibration relations between core and shell are satisfied with the theoretical derivation. Therefore, the Vibration Transmission is significant and it can provide valid method for the DC magnetic bias analysis and core diagnosis of transformer. [ABSTRACT FROM AUTHOR]

Although a rectangular waveguide coupler has the conceptual advantages of simplicity and capability of withstanding higher power, builders of modern superconducting accelerators are routinely choosing instead a coaxial coupler for its proven performance. Multipacting induced discharge has been found to be an operating mechanism that prevents a rectangular waveguide coupler from reaching its full potential. Earlier calculations predicted the existence of two-sided multipacting in a rectangular waveguide geometry. In the present study, special waveguide sections of CESR type were built and tested. Multipacting characteristics of the waveguide were identified. Two multipacting suppression methods, the slotted waveguide method and the DC magnetic bias method, were experimentally evaluated. The multipacting current is suppressed by a factor of more than 2 by opening a slot on the broad wall. Complete multipacting suppression can be realized by using the DC magnetic bias method. [Copyright &y& Elsevier]