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Phase-control technology, which is also called simultaneous interconnection technology, is one of the latest developments in intelligent interconnection. With the subsequent development of the short-circuit system, which increased significantly, the switching capacity of the switch is tested. Applying arc power to the contact holes during a short circuit also causes extensive damage to the switch contacts, which severely affects the operation and life of the switch. To solve this problem, this paper introduces the branch definition algorithm, describes different types of faults occurring in power systems, proposes a general scheme for fault current phase-controlled breaking, derives a fault occurrence detection method and a phase control method, and performs a simulation analysis of the proposed branch definition algorithm; a single-phase short-circuit current model is built; and the algorithm is tested using simulation data. The oscilloscope acquisition data were simulated and analyzed to obtain the characteristic parameters of the waveform, and the online simulation results obtained were analyzed with the oscilloscope data. The experimental results show that the system designed in this paper can accurately predict the zero value, and the zero values obtained from four experiments conducted are 34.52 ms, 34.46 ms, 29.9 ms, and 29.84 ms, respectively. [ABSTRACT FROM AUTHOR]

As a storage method for a distributed storage system, an erasure code can save storage space and repair the data of failed nodes. However, most studies that discuss the repair of fault nodes in the erasure code mode only focus on the condition that the bandwidth of heterogeneous links restricts the repair rate but ignore the condition that the storage node is heterogeneous, the cost of repair traffic in the repair process, and the influence of the failure of secondary nodes on the repair process. An optimal repair strategy based on the minimum storage regenerative (MSR) code and a hybrid genetic algorithm is proposed for single-node fault scenarios to solve the above problems. In this work, the single-node data repair problem is modeled as an optimization problem of an optimal Steiner tree with constraints considering heterogeneous link bandwidth and heterogeneous node processing capacity and takes repair traffic and repair delay as optimization objectives. After that, a hybrid genetic algorithm is designed to solve the problem. The experimental results show that under the same scales used in the MSR code cases, our approach has good robustness and its repair delay decreases by 10% and 55% compared with the conventional tree repair topology and star repair topology, respectively; the repair flow increases by 10% compared with the star topology, and the flow rate of the conventional tree repair topology decreases by 40%. [ABSTRACT FROM AUTHOR]

The hydrophilic surface of fumed nanosilica was modified to a hydrophobic surface by treating it with a trimethyl silane coupling agent, and epoxy nanocomposites were prepared by mixing the modified nanosilica (0 phr, 1 phr, 3 phr, 5 phr, and 7 phr) in an epoxy matrix, where the unit phr means the parts per one hundred grams of epoxy base resin. To apply the nanocomposites to heavy electrical equipment, the effects of the modified nanosilica on the long-term treeing phenomena and the partial discharge (PD) resistance were studied under high voltage alternating current (HVAC) conditions. The bonding of trimethyl silane on the nanosilica surface was confirmed by the appearance of new peaks for the CH2 and CH3 groups in Fourier-transform infrared spectroscopy analysis. To observe the even dispersion of the modified nanosilica particles in the epoxy matrix, a transmission electron microscope was employed, and it was found that 1 phr of the modified nanosilica was uniformly dispersed; however, as the nanosilica content was increased, its aggregation became somewhat severe. The longest HVAC treeing breakdown time was found in an epoxy nanocomposite with 1 phr of alkyl-modified nanosilica, and the time was 17,412 min, which was 143.9 times longer than the 121 min required for a neat epoxy system. In a nanocomposite with 5 phr of modified nanosilica, PD resistance was found to be 12.5 times higher than that of the neat epoxy system. [ABSTRACT FROM AUTHOR]

The calculation of an electric field distribution provides the basis for the structural design of the insulation, and an accurate characterization of conductivity as a function of temperature and electric field forms an important basis for the simulation of the electric field distribution in HVDC (high-voltage direct current) cables. However, the conductivity functions that describe the insulating materials used for HVDC cables in different studies are different, and very little has been reported regarding how to choose the most accurate function. In this work, the conductivity of insulating materials used for HVDC cables is characterized, and the effects of the conductivity characterization on the simulation of the electric field in HVDC cables are studied. First, eight common conductivity functions are compared qualitatively. Then, the conductivities of XLPE for different temperatures and electric fields are measured, and a data fitting technique is used to analyze the coincidence degree between different functions and the test results. Finally, the steady-state electric field distributions of HVDC cables for different temperature gradients are simulated in COMSOL Multiphysics. The results show that the sum of the square of the relative errors of the fitting when using the original functions is larger than that achieved when using the logarithmic form of the functions. The deviations in the electric field caused by taking the logarithm of different functions are smaller. [ABSTRACT FROM AUTHOR]

Based on the slice materials of 35 kV and 110 kV XLPE cables, an experimental platform is built to study the relationship between electrical tree and PDs in XLPE with different voltage levels. There are three significant statistical characteristics of the PDs during the growth of electrical trees. The analysis of the results shows that each growth stage has certain characteristics. Different features existed between the growth of the electrical trees and the PD in the insulation of the 35 and 110 kV cables. Evident characteristics such as large spans of time and frequency were present as the electrical trees grew violently in the equivalent time-frequency diagram at every stage. These results could provide criteria for the identification of the deterioration using PD to monitor cables in service at rated voltages. The results are important for the identification of defects in cable insulation in order to provide an early warning of insulation breakdown in the cables. [ABSTRACT FROM AUTHOR]

Electrical trees are characterized by a technique of fractal characteristics in pattern formation for decades. The geometrical patterns of dielectric breakdown such as lightning discharge, surface discharges, and electrical trees are known to be fractal in nature. It is well known that the electrical trees are frequently occurring in insulating materials. The present investigation deals mainly with the fractal properties of 2D (Dimension) patterns of real electrical tree obtained in insulating materials. The electrical tree patterns are generated experimentally under AC and DC of different voltage levels. The time of voltage application is noted, and the leakage current is measured using digital storage oscilloscope. A charge-coupled device (CCD) camera is used to record the propagation of electrical tree during the experiment. C++ is used to calculate the fractal dimension for experimentally obtained electrical trees by using box counting method. It is found that fractal dimension is a function of magnitude of the voltage, treeing time, and leakage current. Fractal analysis is a good and suitable tool for the analysis of electrical treeing. Copyright © 2014 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]