一则避雷器起火现象浅析

文中结合中国联通公司漯河分公司某基站避雷器起火引起的基站火灾,分析了避雷器起火的原因,并针对此类问题给出了解决方案。     

通信局站用电源避雷器标准中的几个重要技术问题

通信局站低压配电系统保护用电源避雷器(也可称电涌保护器,SPD)是保护通信电源设备及其他通信设备的重要防雷设备,在各种通信局站和机房及电源设备内得到了广泛应用。该产品的种类繁多、保护模式多种多样,致使电源避雷器的通信行业标准一直无法确定下来。在电源避雷器的生产制造和通信部门的使用过程中都已出现了一些混乱的局面,不但防雷保护效果差,甚至还出现很多电源避雷器起火自毁的严重安全事故。在信息产业部和电信运营商的共同关心下,广东省电信公司科学技术研究院(中国电信集团广州研发中心)会同其他相关单位,于2002年年底制定了信…     

通信局（站）用电源避雷器标准的一些重要技术问题的说明

通信局(站)低压配电系统保护用电源避雷器(也可称电涌保护器SPD)是保护通信电源设备及其他通信设备的重要防雷产品，在各种通信局(站)和机房及电源设备内得到了广泛应用。该产品的种类繁多，保护模式多种多样，使用过程中也出现了一些混乱的情况，不但防雷保护效果差，甚至还出现了很多电源避雷器起火焚毁的严重安全事故。     

通信局(站)用电源避雷器标准中一些重要技术问题的说明

1概述通信局(站)低压配电系统保护用电源避雷器(也可称电涌保护器SPD)是保护通信电源设备及其他通信设备的重要防雷产品,在各种通信局(站)和机房及电源设备内得到了广泛应用。该产品的种类繁多,保护模式多种多样,使用过程中也出现了一些混乱的情况,不但防雷保护效果差,甚至还出现了很多电源避雷器起火焚毁的严重安全事故。为了进一步规范电源避雷器的生产和使用,在信息产业部和电信运营公司的共同关心下,广东省电信公司科学技术研究院、中国电信集团广州研发中心会同相关单位,于2002年底制定了相关的中华人民共和国通信行业:《通信局(站)…     

网络安全隐患严重动力系统需防患于未然——艾默生网络能源"动力前线"专业呵护"网络心脏"

网络动力作为网络系统的心脏、网络持续稳定运行的生命线,在为网络提供澎湃动力保障的同时,也暗藏着可能造成网络中断的隐患.在几大通信运营商中,每年都会发生数次因动力系统故障引起的较大范围通信中断.基站、小区级的通信中断更是几乎天天有.因为动力设备起火而烧毁机房所有设备的恶性事件也时有发生.     

基于正样本学习的变电站避雷器破损识别方法

为解决变电站避雷器破损样本图片少,图像识别成功率低的问题,提出了一种基于正样本学习的变电站避雷器破损识别方法。对变电站避雷器图像数据进行噪声过滤,消除环境因素对识别的影响,检测识别避雷器的边缘,并提取避雷器图像区域数据。在此基础上,采用卷积神经网络对正常的避雷器图片进行学习,获得正样本重建数据。并将当前避雷器图像与正样本进行比较,从而对破损避雷器进行识别。将该方法应用于在某地区变电站,实际识别成功率为96.8%;其结果验证了文中所提方法的有效性。     

交流滤波器场内避雷底座绝缘缺陷分析与结构改进

我国高压输电线路建设经历时间长,跨度大,很多变电站、换流站和电厂采用分立式避雷器绝缘底座结构较多,绝缘缺陷问题时有发生。介绍了换流站交流滤波器场内避雷器特点;分析了避雷器绝缘底座缺陷问题;对避雷器绝缘底座提出了解决方法,实施了绝缘结构的改进措施。高压变电站安全运行,需要不断加强监测,保障监测数据的准确性,及时加强日常巡检,尤其是避雷器绝缘性能,确保避雷器的稳定性和安全性,降低因缺陷问题造成的事故。     

110kV氧化锌避雷器运行异常分析及对策

介绍了一起110kV氧化锌避雷器异常运行的隐患,并对此展开分析,进行避雷器解体试验发现异常的原因.针对问题症结,提出一系列防范氧化锌避雷器异常运行的措施,旨在为电力运行部门提供一些思路,确保110kV氧化锌避雷器的安全稳定运行.     

一起变电站220kV线路避雷器故障原因及其处理方法分析

本文通过对一组220kV线路故障避雷器进行解体,结合红外、紫外检测对该组避雷器进行故障原因分析,总结了避雷器故障分析的一些经验体会.     

浅析氧化锌避雷器

本文作者较详细地分析了氧化锌避雷器的工作原理、优点及主要功能,并提出了氧化锌避雷器在选用上和使用中需要注意的问题,利于电力工作者全面了解和使用氧化锌避雷器。     

Identification of the source of an interferer by comparison with known carriers using a single satellite

We describe a method for identifying the source of a satellite interferer using a single satellite. The technique relies on the fact that the strength of a carrier signal measured at the downlink station varies with time due to a number of factors, and we use a quantum‐inspired algorithm to compute a “signature” for a signal, which captures part of the pattern of variation that is a characteristic of the uplink antenna. We define a distance measure to numerically quantify the degree of similarity between two signatures, and by computing the distances between the signature for an interfering carrier and the signatures of the known carriers being relayed by the same satellite at the same time, we can identify the antenna that the interferer originated from, if a known carrier is being relayed from it. As a proof of concept, we evaluate the performance of the technique using a simple statistical model applied to measured carrier data.     

一种安全的纠错网络编码

该文利用消息空间的所有子空间上的一种度量,给出了一种安全的纠错网络编码。首先,此度量下的最小距离译码法可以纠正一定维数的错误。另外,在此编码方法下,当攻击者能窃听到的信道数目小于网络的最大流时,攻击者得不到关于信源的任何信息。最后,当攻击者能窃听网络中所有信道时,本文通过让信源和信宿共享一个随机数生成器和一个秘钥,进一步给出了能防此类强攻击者的安全纠错网络编码。     

多路径环境下电信流量模型研究

在下一代通信网络中,一个终端可同时拥有多个网络接口,在一对源、目的终端间存在多条可用路径。这为网络通信提供了一种全新的思路,即利用多条路径并发进行数据传输。针对多路径传输出现的问题,文章为多路径传输建立了流量模型,分析了多路径传输流媒体的优势,提出了＂流体带宽＂和＂流体调度＂的概念,并引入网络流理论计算了多路径环境下的目标流量。     

A quad-rotor system for driving and flying missions by tilting mechanism of rotors: From design to control

This article presents the hybrid design and control of a quad-rotor system called Flymobile. Flymobile is a combined system of a mobile robot and a quad-rotor system aimed to perform both flying and driving tasks. Flymobile performs flying tasks in the same way as conventional quad-rotor systems while the tilting mechanism of each rotor allows Flymobile to navigate in its terrain for a driving task. The body frame with rotors is implemented by a calibration process through a test-bed equipped with a force sensor. The triangular wheel frame is designed to mimic motions of a mobile robot with three passive wheels. Sensor data of a gyro and an accelerometer are filtered and used for controlling the attitude of the system. Focusing on a practical approach of implementing a hybrid system, a non model-based approach is applied to control Flymobile. Experimental studies are demonstrated to show the feasibility of performing both driving and flying missions.     

Virtual impedance control for a regional dynamic voltage restorer

A dynamic voltage restorer (DVR) can be installed in a middle-voltage (MV) power grid, to concurrently protect a cluster of sensitive loads from voltage sags. To further improve its efficiency and reduce the difficulty in its implementation, a novel control strategy for operating such a DVR as a virtual impedance in series with sensitive loads is proposed in this paper. In addition to its usual function of compensating for voltage sags, such a DVR can also operate as a virtual inductance, to function as a fault current limiter (FCL) during a downstream fault, or a virtual capacitance, to function as a series compensator (SC) to compensate the voltage loss along the feeder line during heavy load. Based on a dual-loop control design, strategies for operating a DVR as a series virtual inductance and a virtual capacitance are proposed, and methods for tuning the parameter values and a stability analysis of the whole system are presented. The feasibility and effectiveness of the proposed method are verified by simulations using the PSCAD software, and experimental results obtained using a prototype DVR are presented.     

Delay Analysis of All-Optical Packet-Switching Ring and Bus Communications Networks

We study the delay performance of all-optical packet communication networks configured as ring and bus topologies employing cross-connect switches (or wavelength routers). Under a cross-connect network implementation, a packet experiences no (or minimal) internal queueing delays. Thus, the network can be implemented by high speed all-optical components. We further assume a packet-switched network operation, such as that using a slotted ring or bus access methods. In this case, a packet's delay is known before it is fed into the network. This can be used to determine if a packet must be dropped (when its end-to-end delay requirement is not met) at the time it accesses the network. It also leads to better utilization of network capacity resources. We also derive the delay performance for networks under a store-and-forward network operation. We show these implementations to yield very close average end-to-end packet queueing delay performance. We note that a cross-connect network operation can yield a somewhat higher queueing delay variance levels. However, the mean queueing delay for all traffic flows are the same for a cross-connect network operation (under equal nodal traffic loading), while that in a store-and-forward network increases as the path length increases. For a ring network loaded by a uniform traffic matrix, the queueing delay incurred by 90% of the packets in a cross-connect network may be lower than that experienced in a store-and-forward network. We also study a store-and-forward network operation under a nodal round robin (fair queueing) scheduling policy. We show the variance performance of the packet queueing delay for such a network to be close to that exhibited by a cross-connect (all-optical) network.     

X波段GaN HEMT内匹配器件

自主研制的GaN HEMT,栅源泄漏电流从1E-4A量级减小到了1E-6A量级,有效提高了栅漏击穿电压,改善了器件工作特性. 采用MIS结构制作了2.5mm栅宽GaN HEMT,测试频率为8GHz,漏源电压为33V时,器件连续波输出功率为18.2W,功率增益为7.6dB,峰值功率附加效率为43.0%. 2.5mm×4 GaN HEMT内匹配器件,测试频率8GHz,连续波输出功率64.5W,功率增益7.2dB,功率附加效率39%.     

A library-based synthesis methodology for reversible logic

Synthesis of reversible logic has received significant attention in the recent years and many synthesis approaches for reversible circuits have been proposed so far. In this paper, a library-based synthesis methodology for reversible circuits is proposed where a reversible specification is considered as a permutation comprising a set of cycles. To this end, a pre-synthesis optimization step is introduced to construct a reversible specification from an irreversible function. In addition, a cycle-based representation model is presented to be used as an intermediate format in the proposed synthesis methodology. The selected intermediate format serves as a focal point for all potential representation models.In order to synthesize a given function, a library containing seven building blocks is used where each building block is a cycle of length less than 6. To synthesize large cycles, we also propose a decomposition algorithm which produces all possible minimal and inequivalent factorizations for a given cycle of length greater than 5. All decompositions contain the maximum number of disjoint cycles. The generated decompositions are used in conjunction with a novel cycle assignment algorithm which is proposed based on the graph matching problem to select the best possible cycle pairs. Then, each pair is synthesized by using the available components of the library. The decomposition algorithm together with the cycle assignment method are considered as a binding method which selects a building block from the library for each cycle. Finally, a post-synthesis optimization step is introduced to optimize the synthesis results in terms of different costs.To analyze the proposed methodology, various experiments are performed. Our analyses on the available reversible benchmark functions reveal that the proposed library-based synthesis methodology can produce low-cost circuits in some cases compared with the current approaches. The proposed methodology always converges and it typically synthesizes a give function fast. No garbage line is used for even permutations.     

Six d.o.f. displacement measuring device based on a modified Stewart platform

Acquisition of the displacements and deformations of a loaded component is generally a not easy operation. This is especially the case as the component often presents a complex geometry and the deformations involve more degrees of freedom or a combination of them.Measurement devices used for this kind of application often allow to obtain simplified measurements.This paper presents a novel measurement device, consisting of six displacement sensors mounted as a parallel mechanism, capable to measure the global deformation of a component in terms of translations and rotations. The deformations are obtained by applying the direct kinematic equations to convert the six displacements read from the six sensors into the three translations and rotations representing the deformation of the component.The geometry of the device leads to write simplified equations for the direct kinematic that can be solved with a semi-numerical procedure implemented in a program written in Matlab environment.The results given by this procedure have been validated with the positions obtained from a 3D CAD model of the device, showing perfect agreement between the results.A prototype has been made and tested on a workbench.     

New formulation of GNSS acquisition with CFAR detection

This paper deals with the analysis of the acquisition process performed by a global navigation satellite system (GNSS) receiver with a pilot and data channel or in case of GNSS hybrid receiver. Signal acquisition decides the presence or absence of GNSS signal by comparing signal under test with a fixed threshold and provides a code delay and a Doppler frequency estimation, but in low signal conditions or in a noisy environment; acquisition systems are vulnerable and can give a high false alarm and low detection probability. Firstly, we introduce a cell‐averaging‐constant false alarm rate (CFAR) then a data‐pilot cell‐averaging‐CFAR detector fusion based to deal with these situations. In this context, we use a new mathematical derivation to develop a closed‐form analytic expressions for the probabilities of detection and false alarm. The performances of the proposed detector are evaluated and compared with a non‐CFAR case through an analytical and numerical results validated by Mont Carlo simulations. Copyright © 2016 John Wiley & Sons, Ltd.