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Copyright of Przegląd Elektrotechniczny is the property of Przeglad Elektrotechniczny and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Journal of Liaoning Technical University (Natural Science Edition) / Liaoning Gongcheng Jishu Daxue Xuebao (Ziran Kexue Ban) is the property of Journal of Liaoning Technical University (Natural Science) Editorial Department and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Contact failure as one of primary failures, which occurs between thin film resistance strain gauge (FRSG) and metal measured objective substrate, seriously influences the measurement validity and precision of the strain gauge. In this article, an electrical excitation thermal-wave imaging (EE-TWI) method is proposed for the inspection of contact failure. Equivalent circuits of the contact resistance under an external electrical source are used to identify the location of the contact failure. Long pulse thermography and lock-in thermography (LIT) are experimentally studied on the detection of contact failure. Pulsed phase thermography and principal component thermography in long pulse thermography as well as the amplitude, quadrature component in LIT are desirable to form the EE-TWI feature images, respectively. A graph-based segmentation method is employed to distinguish and localize the contact failure from EE-TWI images. EE-TWI provides a powerful tool for the contact failure evaluation of integrated thin film resistance strain gauge (FRSG) and has a significant potential to ensure the thin FRSG sticking performance and quality with application of mechanical properties measurements. [ABSTRACT FROM AUTHOR]

Electrical connectors are widely used in electrical devices as an interconnect element and their reliability is a critical factor in device performance. However, there are multiple factors that may lead to poor reliability. These include contact failure induced by temperature and humidity, vibration, and atmospheric contamination, which may induce deterioration of the transmitted signal and leakage of electromagnetic energy. In the current work, the contact failure characteristics of a specific connector are investigated through measurement and analysis of high frequency parameters and spectrums. Based on transmission line theory and electrical contact theory, an equivalent model was developed to explore the effect of contact failure on high frequency parameters. Experiments were conducted using a network analyzer, signal generator, signal analyzer, and H‐field probe. The high frequency parameters were measured and compared with the calculated values, with consistent results. The leakage spectrums were measured with an H‐field probe for a variety of input signal amplitudes and frequencies and loose contact conditions. The results indicate that leakage increases with higher frequency and greater input signal amplitude. [ABSTRACT FROM AUTHOR]

Overheating faults of gas-insulated bus (GIB) plug-in connectors induced by contact degradation seriously threaten the safe operation of equipment and power system. Multiphysics coupled numerical simulations and physical experiments were conducted in this article to reveal contact degradation processes of the GIB plug-in connector. First, electromagnetic-thermal-mechanical coupled finite-element (FE) model was built. Relative motion between contact interfaces was considered by low-velocity Stribeck friction model. FE model was verified by physical experiment. Second, influences of operation current, spring stiffness, and conductor insert depth on contact temperature rise were analyzed. Results show that insufficient conductor could induce overheating on several contact spots then accelerate the degradation process. Third, thermal and motion characteristics under cyclic operation currents and short-circuit (SC) current impact were analyzed. Results show that conductor insert depth could be changed by relative motion between contact elements. Relative motion accumulates gradually under cyclic thermal loading by operation current. Significant relative motion and temperature rise could be induced by SC current impact. Finally, progressive and sudden failure mechanisms of the GIB plug-in connector were discussed. Research result may guide optimal design and field maintenance of GIB equipment, and thus improves its reliability. [ABSTRACT FROM AUTHOR]

In order to provide an effective detection method for internal contact fault of gas insulated bus (GIB), mechanical and magnetic field behaviors of GIB plug-in connector under different assembly conditions are analyzed by finite element (FEM) method in this paper. Contact forces on individual contact spots are obtained by mechanical field analysis then simulated by imperfect contact bridge models during electromagnetic field analysis. Magnetic field distributions around GIB plug-in connector under the various contact statuses (conductor insert depth and docking angle) are studied through numerical modeling and field testing. Results show that the mechanical contact parameters (contact forces and radiuses) of individual contact fingers vary from each other under the action of holding spring deformation and conductor gravity, and the surrounding magnetic field has strong relationship with the internal mechanical contact status. The magnetic field strength distributes uniformly around the GIB plug-in connector under well assembly condition. However, the magnetic field distorts since mechanical contact status is changed by the contact degradation or contact failure. [ABSTRACT FROM AUTHOR]

Serious environmental pollution degraded the reliability of gold-plated connectors in many-handed terminals. It was found that gold-plated contacts disassembled from failed mobile phones were tarnished and worn out. The main compositions of the contaminants on the failed contacts were dust particles, organic compounds, and worn contact materials with their oxide. The micromotion between contacts abrasively wore the contacts with the dust particles and organic compounds. Contact resistance on the tarnished contacts increased with the thickness of contaminants on the contacts. The combined effects of dust particles, organic compounds, and micromotion on the electrical behaviors of the gold-plated contacts were simulated and studied by adapting a fretting simulation system. The hard particles caused seriously abrasive wear of gold plating and quickly formed fretting corrosion to shorten the contact life. Tiny content of organic compounds supplied certain adhesion function of dust particles, which made it easy for the dust particles to insert the contact interfaces. The contaminants and wear debris with their oxide formed complexly tarnished morphology under micromotion conditions, which finally caused contact failure. [ABSTRACT FROM AUTHOR]

To explain contact failure phenomena and their development in the gas-insulated switchgear (GIS), tests wee conducted by stimulating abnormal current-carrying conditions using an actual 300-kV, 2000-A GIS. This paper describes the process observed, ranging from contact failures to ground faults, deteriorative phenomena and some detection methods for initial contact failure conditions. A summary of this study is as follows: (1) The contact resistances are greatly dependent on the materials and construction of contacts. (2) The relation between the initial contact resistance and the carried current resulting in arching is derived with approximately constant Joule-heat generation. (3) Ground faults result from sagging of a shield melted by arching or a combination of two causes: (i) scattering of molten metal caused by arcing; and (ii) sagging of conductor caused by bolt melt down. (4) To detect initial contact failures, it is recommended to observe the contact resistance, the temperature rise on the tank surface, or the electrical partial discharges. [ABSTRACT FROM AUTHOR]

Due to their high isolation, low insertion loss, high linearity, and low power consumption, microelectromechanical systems (MEMS) switches have drawn much attention from researchers in recent years. In this paper, we introduce the research status of MEMS switches in different bands and several reliability issues, such as dielectric charging, contact failure, and temperature instability. In this paper, some of the following methods to improve the performance of MEMS switches in high frequency are summarized: (1) utilizing combinations of several switches in series; (2) covering a float metal layer on the dielectric layer; (3) using dielectric layer materials with high dielectric constants and conductor materials with low resistance; (4) developing MEMS switches using T-match and π-match; (5) designing MEMS switches based on bipolar complementary metal–oxide–semiconductor (BiCMOS) technology and reconfigurable MEMS’ surfaces; (6) employing thermal compensation structures, circularly symmetric structures, thermal buckle-beam actuators, molybdenum membrane, and thin-film packaging; (7) selecting Ultra-NanoCrystalline diamond or aluminum nitride dielectric materials and applying a bipolar driving voltage, stoppers, and a double-dielectric-layer structure; and (8) adopting gold alloying with carbon nanotubes (CNTs), hermetic and reliable packaging, and mN-level contact. [ABSTRACT FROM AUTHOR]