[en] Highlights: • An innovative TENG superimposed electrode layers is presented. • Utilizing the edge effect of two charged parallel plates. • One with part of the Al electrode extended as the contact point is proposed. • The I_sc for TENG stacked with four layer electrodes can enhanced remarkably. • The volume can be reduced by 50–80% compared to the traditional TENG. Traditional methods enhancing the output performance of triboelectric nanogenerator (TENG) are mainly by increasing the number of single TENGs mechanically after controlling the materials surface structures and/or chemical modifications. We present an innovative TENG superimposed electrode layers by utilizing the edge effect of two charged parallel plates with poly-l-lactide (PLLA) slice and silicone sheet as the triboelectric materials and the extended part of Al electrode as the connection. When the gap distance (d) between the upper and lower friction surfaces is 1.5 cm, the d/L (L is the lateral size of TENG) is greater than 0.4, the short-circuit current (I_sc) of TENG stacked with four layer electrodes was 3 times larger than that of TENG with one layer electrode. The I_sc reaches a saturation when the number of superimposed electrode layers was beyond eight, corresponding to 3–5 times larger than that with one layer electrode. While the obtained I_sc was 2–5 times larger than that with one layer electrode, the volume of TENG based on superimposed electrode layers can be reduced by 50–80% compared to the traditional TENGs stacked the number of single TENGs. This simple, novel method paves a way for enhancing output current, more miniaturization of the TENG.

[en] With the wide application of the internet and rapid development of the information technology, the scale of the internet data center power network is growing larger and larger. Some of the troubles in the internet data center (IDC) power network may cause extensive service out of service or even collapse. However, without considering the characteristics of the IDC power network, the important node identification methods for the IDC power network based on graph mainly focus on the graph structure itself. Since a large number of automatic switching equipment such as ATS, STS and loop switch have been used in IDC, when the electrical fault occurs, the load will be automatically migrated to the adjacent electrical equipment, which may lead to overloading or even tripping. So the failure is extended. So how can we efficiently and effectively capture the fault evolution mechanism of the IDC power network? How do we go about identifying the vulnerable nodes causing the collapse of the IDC power network.

In this article, we propose DCPNFEM, a novel fault evolution model for the IDC power networks, as well as a fitting algorithm, BCBL, which can solve the proposed problems. Our algorithms have the following properties: (a) Intuitively: it detects fault evolution mechanism, such as power load migration, electrical equipment tripping, and so on; (b) Timely: our method is based on the real-time power loads; (c) General: our algorithms are general and practical, which can be used in various power network topologies, including data center infrastructures from tier1 to tier4.

Extensive experiments on a real IDC power network demonstrate that some particular nodes’ failure can lead to the power network crash under DCPNFEM. And BCBL algorithm outperforms better accuracy and speed than many other algorithms. (paper)

[en] Methods are proposed for measuring the resistance and impedance of the welding circuit in contact machines; the machine may be switched on in short-circuit mode. Methods are outlined for measuring and calculating the basic electrical parameters.

[en] A method of increasing the sensitivity of protection from single-phase short-circuits to ground by acting on the signal with brief dummy grounding of the neutral is described. After determining the damage, the neutral is again grounded through a high resistance and an arc-quenching reactor. An increase in the protection sensitivity is thereby obtained, the damage detection time is shortened, and the probability of the single-phase short-circuit to ground converting into double and multipoint earth faults is reduced.

[en] Dry-type air-core reactor has frequent faults due to insulation aging in long-term operation, among which the inter-turn short circuit fault rate is the highest. Firstly, the equivalent circuit model of reactor inter-turn short-circuit fault is established, and the characteristics of reactor power angle change caused by inter-turn short-circuit fault are analyzed. Based on this, an on-line monitoring technology of dry air-core reactor inter-turn short-circuit based on impedance micro-incremental identification is proposed. The power factor angle of the reactor is obtained by impedance micro-incremental analysis. The test results show that the proposed technology can effectively monitor the short circuit fault of the reactor with less turn-to-turn insulation. (paper)

[en] We report on the key role of the acoustical impedance ratio between the solid and the host fluid in the transmission properties of slit arrays. Numerical calculations predict huge sound screening effects up to 60 dB for low impedance ratio values. The screening band appears over a broad frequency region and is very robust against dissipative losses of the material as well as against the sound incident angle. This counterintuitive result is discussed in terms of the hydrodynamic short circuit, where the fluid and the solid at the radiating interface vibrate out of phase, resulting in a huge sound blocking effect.

[en] Long-lasting problems concerning peculiar statistical behaviour of high populated electron avalanches have been analysed. These avalanches are precursors of streamer breakdown in gases. The present streamer theory fails in explaining severe systematic deviations from the Furry statistics that is believed to be a governing statistical law. Such a deviated behaviour of high populated avalanches seems to be a consequence of a special pre-breakdown mechanism that is rather different from that known so far in discharge physics. This analysis tends towards formulating a modified theoretical concept supplementing the streamer theory by a new statistical view of pre-streamer states. The correctness of the concept is corroborated by a series of experiments

[en] Magnetic tunnel junctions may experience failure due to local shortcuts in the insulating layers of such devices. The quality of the insulating layers of these devices must be analyzed. We use electrodeposition to decorate pinholes and analyze the density of pinholes and pinhole precursors. Electrical breakdown measurements can also be performed on magnetic tunnel junctions to predict the probability of such devices failing. We discuss both experimental methods and compare the results obtained. It is observed that the two methods yield the same results for the areal defect density. [copyright] 2001 American Institute of Physics

[en] A current-limiting coil with a core made of superconducting high-Tc material is tested with a view to application as a short-circuit current limiter in a three-phase network. According to the current limiter concept, the coil core is a superconductor during rated current operation, and thus keeps the coil inductance low by means of the screening effects. Under overload conditions, the magnetic field of the core winding reduces the core to normal conductivity, which eliminates the screening effects, increases the inductance, and thus results in current limitation. (orig.)

[en] This paper presents some experimental results obtained with the plasma focus PFMA-1 operated at about 20.5 kV, corresponding to a total capacitor bank energy of about 70 kJ, with ⁴He as working gas and pressure ranging between 50 and 3000 Pa. The aim of the study is the assessment of the differences in pinch performance with and without the adoption of a cathodic knife edge with the role of improving the electrical breakdown and the formation of the initial plasma layer. The pinch performance is estimated with the introduction of a voltage quality factor, which is related to the overvoltage intensity during the pinch, and of a current dip factor, correlated with the sudden total current reduction. More than 1500 shots have been analyzed with a semiautomated numerical special procedure. It is found that the improvement in the pinch efficiency with the use of a cathodic knife edge in these experiments can be even higher than a factor of 2.