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Overhead ground wires installed on transmission lines have been proved to be effective to protect conductors from direct lightning strokes, but ground wire breakouts due to icing are frequently reported. In order to prevent electric failure accidents caused by ground wire breakouts under icing conditions, unshielded transmission lines equipped with metal oxide arresters (MOAs) whole line have been proposed in high mountainous areas. Compared with ordinary transmission lines, lightning stroke risk of unshielded lines is much higher. In order to improve the lightning performance of unshielded lines, it is necessary to obtain the essential lightning energy absorption ability of the MOAs installed on unshielded lines. In this article, simulation model of unshielded 220 kV transmission lines equipped with MOAs is built, the influences of lightning parameters, striking occurrence point and grounding resistance on the absorbed energy of MOAs are analyzed. Based on Monte Carlo method, lightning trip-out rate of unshielded transmission lines are calculated, and suggested energy absorption ability of MOAs is proposed, which can give references for the improvement of power supply reliability of transmission lines. [ABSTRACT FROM AUTHOR]

Lightning strikes and pollution could cause short circuits and tripping of the overhead distribution lines. To alleviate this, a 10-kV post insulator with concentric externally gapped line arrester (EGLA) has been proposed and its performance is studied in service. However, its pollution performance has to be established. This paper studies the AC pollution breakdown characteristics of the EGLA and broaden current knowledge of pollution flashover. Compared with the flashover of the normal insulator, three kinds of specificity of the EGLA were found. Firstly, the pollution flashover process can be divided into three categories. Secondly, the wet flashover voltage, Uf_wet, of the novel insulator is higher than the dry flashover voltage, Uf_dry. Thirdly, the piecewise fitting methods with a × ESDD^−b + d and a × ESDD^−b + c × ESDD^−d are more suitable for fitting the empirical formula of flashover voltage. Furthermore, to explain specificity, the electric potential and electric field distribution are calculated based on the finite element method. Calculated results indicate that when the EGLA is covered with a 0.5mm water film, the maximum electric field intensity decreased from 2.17 kV/cm to 1.99 kV/cm. Also, U_arrester (the withstand voltage of the insulation section) was obtained from the tests and it presents a discontinuous and random increasing trend until flashover occurs, which is considered to be one of the important reasons for the specificity. Besides, based on the Obenaus’ model and Hampton's criterion, we further analyzed the arc development process by a simplified plate model. [ABSTRACT FROM AUTHOR]

Presents a study which described the design of the Impulse computer memory system architecture. Software interface and operating system support of Impulse; Analysis of the sparse matrix-vector multiply; Performance impact of Impulse optimizations.

Convolutional neural network (CNN) is widely used in artificial intelligence for its excellent recognition accuracy. With its scale increasing rapidly and architecture becoming complicated, it is much difficult to implement CNN in hardware platform efficiently. Many FPGA-based CNN accelerators are proposed in previous work. However, when evaluating resource efficiency, their assessment methods are: 1) device related; 2) frequency related; or 3) they confuse resource efficiency with resource occupancy. There is an insistent demand for intuitive and fair assessment criteria. When implementing CNNs, they still have improvement room in computing resource efficiency, especially for layers with large feature size and few feature maps. In this work, we propose Rscore and Cscore, which compose a comprehensive and accurate resource efficiency assessment mechanism for evaluation and design guidance, respectively. Under the guidance, we introduce Cheetah, an FPGA-based high-throughput acceleration architecture. Its computing part can optimize the use of available resources in both time and space aspects, resulting in better throughput improvement. An auxiliary storage system and a pipeline stage compression method are designed for less storage overhead and shorter inference latency. We implement AlexNet and ResNet18 on KCU1500 at 230 and 240 MHz, respectively, with a throughput of 2411.01GOP/s and 2435.05GOP/s for 16-bit quantification. Cheetah achieves an excellent average Rscore of (0.9441, 0.9456) on different FPGA devices, while the others’ mainly distribute between 0.3 and 0.8. Finally, Cheetah has 6.78X speed improvement and 1.87X power-efficiency improvement than that of Nvidia Jetson TX2, which is the fastest, most power-efficient embedded AI computing device. [ABSTRACT FROM AUTHOR]

An 11 T superconducting magnet has been manufactured for a 45 T hybrid magnet, the superconducting magnet has a large room temperature bore of 800 mm, so it can provide an 11 T background field for performance test of cable in conduit conductors (CICC). A test facility for superconducting CICCs has been designed as an insert combined with the superconducting magnet, wherein an 80 kA superconducting transformer has been designed to provide high operating current for the CICC samples. The CICC sample was designed to be a bifilar non-inductive solenoid coil. This paper will describe the principle design of the test facility and the overview of the 80 kA superconducting transformer. [ABSTRACT FROM PUBLISHER]

Ice-covering characteristics are often researched in transportation, communication, and electric power industry. China Hunan Power Grid can easily suffer from ice disaster because of its geographical and climate environment. In particular, in the 2008 ice disaster, icing on overhead transmission lines and facilities caused outage in some cities and counties with a total population of about 30 million people. The ice-covering characteristics of the China Hunan Power Grid were analyzed in this paper. The recorded icing and frost climate data were investigated and analyzed. The model of overhead power line icing was proposed. The ice accretion mechanism was thus revealed. The icing impact factors such as geographical situation, climate characteristics, freezing weather characteristics, microterrain, and elevation were also presented in detail. The necessary conditions for ice-covering formation and the glaze frost distribution of Hunan Province were obtained. [ABSTRACT FROM AUTHOR]