Abstract ：

Intrusion detection is a crucial task in power grid surveillance system by providing early warning for power grid security. Construction machinery and engineering vehicles, as the most common intrusion objects, have become the major concern for preventing external damages in power grid maintenance. In this paper, by considering the diversity of scales of intrusion objects and complexity of application scenarios under power grid surveillance, we compiled a dataset which contains 8177 images captured by 653 different power grid surveillance cameras. Based on this dataset, we proposed an improved context-aware mask region-based convolutional neural network (Mask R-CNN) model, namely ID-Net, for intrusion object detection. A modulated deformable convolutional operation is integrated into the backbone network for learning robust feature representations from geometric variations in engineering vehicles. By considering the correlation between objects and their context, a self-attention-based module is leveraged for long-range context relation modeling. For small objects detection, a feature integration module is applied for multi-scale feature fusion under a pyramid hierarchy. Then, a cascaded coarse-to-fine region proposal network is incorporated for progressively refining the bounding box location regression. Experimental results have demonstrated that our model can achieve competitive performance in comparison with state-of-the-art object detection methods.

Keyword ：

Construction machinery detection Engineering vehicle detection Intrusion detection Power grid surveillance

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Abstract ：

我国自主研发生产的植物绝缘油目前只应用在最高电压等级为35 kV的变压器中,缺乏国产植物绝缘油大间隙下击穿特性的试验数据支撑是限制其应用于更高电压等级变压器中的重要原因。本研究对比了进口、国产植物绝缘油和国产矿物绝缘油在雷电冲击电压和直流电压下的击穿特性。结果表明:国产植物绝缘油与进口植物绝缘油具有相似的雷电冲击和直流击穿特性。正极性下,植物绝缘油小间隙下(<25 mm)的击穿电压与矿物绝缘油相当甚至优于矿物绝缘油,但大间隙下矿物绝缘油的击穿电压优势更明显,此外,绝缘油在直流和雷电冲击电压下的击穿电压没有明显差异。负极性下,矿物绝缘油的击穿电压始终高于植物绝缘油,并且绝缘油的直流冲击击穿电压明显高于雷电击穿电压。

Keyword ：

大间隙 非均匀电场 雷电冲击击穿 植物绝缘油 直流击穿

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Abstract ：

我国自主研发生产的植物绝缘油目前只应用在最高电压等级为35 kV的变压器中,缺乏国产植物绝缘油大间隙下击穿特性的试验数据支撑是限制其应用于更高电压等级变压器中的重要原因。本研究对比了进口、国产植物绝缘油和国产矿物绝缘油在雷电冲击电压和直流电压下的击穿特性。结果表明:国产植物绝缘油与进口植物绝缘油具有相似的雷电冲击和直流击穿特性。正极性下,植物绝缘油小间隙下(<25 mm)的击穿电压与矿物绝缘油相当甚至优于矿物绝缘油,但大间隙下矿物绝缘油的击穿电压优势更明显,此外,绝缘油在直流和雷电冲击电压下的击穿电压没有明显差异。负极性下,矿物绝缘油的击穿电压始终高于植物绝缘油,并且绝缘油的直流冲击击穿电压明...

Keyword ：

大间隙 非均匀电场 雷电冲击击穿 植物绝缘油 直流击穿

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Abstract ：

Conductive particles are one of the most important defects which can greatly degrade the performance of gas-insulated metal-enclosed switchgear (GIS). Many efforts have been made to clarify the influence on the withstand voltage, understand the flashover mechanism, and build a comprehensive model to describe the particle-initiated flashover. In this study, a partial discharge (PD) signal detected through a photomultiplier (PMT) and recorded by a high-speed data acquisition (DAQ) system was used to analyze the discharge development of a conductive particlecontaminated GIS insulator under constant high AC voltage. An additional PMT was used as a reference to eliminate the dark count of the PMT and the data collection method of a DAQ system was optimized to capture the pulse waveform of each PD to obtain detailed physical information. Spectra of the PD pulse amplitude over pulse width, PD counts within various amplitude ranges over time and phase resolved partial discharge (PRPD) patterns of the PDs in different stages are obtained through the captured PD waveforms. Characteristics of the PDs from the application of the high AC voltage up to the flashover of the insulator were then analyzed, and it was found that the features of the PDs in the near-flashover stage were significantly different to the previous stages. © 2020 MDPI AG. All rights reserved.

Keyword ：

Data acquisition Flashover Partial discharges

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Abstract ：

以圆形引线最小绝缘距离表中的10 kV引线结构为研究对象,采用COMSOL软件进行三维有限元电场仿真,并使用实物模型进行不同结构的绝缘距离试验验证,最终得到10 kV引线的最小绝缘距离,引线绝缘距离均比原有的标准有至少60%以上的降低,提出了适合当代变压器的新的圆形引线最小绝缘距离,为制定新的制造标准提供了参考依据。

Keyword ：

变压器 仿真优化 绝缘距离 圆形引线

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Abstract ：

A practical numerical approach to the analysis of the effects of tolerances fabrication on the performance of a planar 0.35 THz extended interaction oscillator (EIO) is presented. The planar EIO is to be driven by pseudospark-sourced sheet electron beam. The influence of tolerance on the Q-value, resonance frequency, characteristic impedance is demonstrated using an effective value of conductivity of 1.1 × 107 S/m to take into account the skin depth and surface roughness. The method of Wire Electrical Discharge Machining (WEDM) is proposed to manufacture the 0.35 THz EIO because of its precision and moderate cost compared with other manufacturing methods such as high speed micro machining, Deep Reactive Ion Etching (DRIE) or Ultra Violet Lithographie, Galvanik, and Abformung (UV LIGA). © 2019 IEEE.

Keyword ：

Electric discharge machining Electric discharges Electron beams Fabrication Micromachining Millimeter waves Surface roughness Terahertz waves

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Abstract ：

A new design for a power supply module for IGBT driver is presented in this paper. The design, here referred to electric isolation, is based on a flyback converter and a front-end power factor correction (PFC). The power supply module eliminates the effects of voltage difference between emitters of two IGBTs in series. To set up the module, L6561 chip is used to control the MOSFET in the flyback circuit. Besides, a series connected IGBT switch with a maximum blocking voltage of 40kV is implemented based on the proposed module. Finally, the switch is used to generate the damped AC (DAC) voltage on a 10kV power cable connected with a reactor and a HVDC generator. The results indicate that the power supply module can stably generate 18V voltage and the IGBT can work normally to generate predetermined DAC voltage on the cable.

Keyword ：

DAC electric isolated power supply high voltage switch

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Abstract ：

选取国产植物绝缘油RAPO、进口植物绝缘油FR3以及传统矿物绝缘油25#为研究对象,研究了工频交流电压下绝缘油种类、间隙距离对绝缘油击穿特性和油纸沿面闪络特性的影响,分析了工频交流电压下绝缘油击穿电压和油纸沿面闪络电压之间的差异,并通过电场仿真探究了绝缘油击穿电压和油纸沿面闪络电压之间产生差异的原因。结果表明:当间隙距离较小(<15 mm)时,植物绝缘油的击穿电压高于矿物绝缘油,但随着间隙距离的增大,矿物绝缘油的击穿电压逐渐超过植物绝缘油;3种绝缘油的油纸沿面闪络电压没有体现出明显的大小关系;绝缘油击穿电压始终明显高于油纸沿面闪络电压。

Keyword ：

大间隙 放电特性 油浸绝缘纸板沿面 植物绝缘油

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Abstract ：

以圆形引线最小绝缘距离表中的10 kV引线结构为研究对象,采用COMSOL软件进行三维有限元电场仿真,并使用实物模型进行不同结构的绝缘距离试验验证,最终得到10 kV引线的最小绝缘距离,引线绝缘距离均比原有的标准有至少60%以上的降低,提出了适合当代变压器的新的圆形引线最小绝缘距离,为制定新的制造标准提供了参考依据。

Keyword ：

变压器 仿真优化 绝缘距离 圆形引线

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Large currents are injected into the earth from grounding poles of HVDC systems under monopole ground return mode. The currents change the earth surface potential and result in DC currents in AC systems. This paper proposes a computationally efficient decoupled circuital calculation method for assessing the unwanted DC currents in AC grids. Firstly, the earth resistive network is acquired by simulating the DC grounding current distribution using Finite Element Method (FEM). Secondly, the earth resistive network and AC grid are combined to develop a decoupled circuital model of the overall system. The acquired model is used to calculate the DC currents in AC grids by solving a set of linear equations. The proposed method is computationally more efficient as compared to field-circuit coupled methods. In addition, its accuracy is proved by showing a close agreement between our results and field-circuit coupled model as well as the actual measurements. Finally, in Shanghai area power grid the DC currents are calculated using the proposed technique. Based on these calculations, remedial measures for reducing the DC currents in AC grid are suggested. Our research results indicate that DC currents in AC systems can be reduced by operating the two HVDC projects with opposite polarities.

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