A growing number of fires and explosions in energy storage plants have been triggered by the thermal runaway of lithium-ion batteries. Owing to the complex physicochemical properties of these batteries, their fire safety issues remain unresolved and constitute a major obstacle to the large-scale deployment of energy storage systems. Compared with conventional extinguishing media, liquid nitrogen (LN2) offers a dual suppression mechanism, i.e., rapid endothermic vaporization and oxygen displacement by inert nitrogen gas, making it highly suitable for lithium-ion battery fire control. However, the key operational parameters governing its suppression efficiency remain unclear, leading to excessive or insufficient LN2 use in practice. This study established a dedicated experimental platform and designed 10 experimental conditions, each repeated three times, to investigate the propagation of thermal runaway between adjacent batteries and to quantify the suppression performance of LN2 under varying nozzle diameters and injection strategies. Results demonstrate that under identical injection pressures, larger nozzle diameters significantly outperform smaller ones in cooling and suppression efficiency. The optimal nozzle diameter was found to be 14 mm, achieving a cooling efficiency of 40%. Furthermore, intermittent LN2 injection of equal total mass outperformed continuous injection, with a 45 s intermittent duration achieving a cooling efficiency of 63%, 23% higher than continuous injection. These findings provide quantitative guidance for the design of LN2-based suppression systems in large-scale lithium-ion battery energy storage modules.

In recent years, there have been multiple incidents of fracture faults caused by the deterioration of composite insulators in China, seriously threatening the safe operation of the power system. This article takes a 500 kV decay-like composite insulator collected from the operation site as the research object, conducts visual inspection and analysis of its shed and core rod degradation status, and tests its infrared temperature rise and ultraviolet discharge distribution under power frequency operating voltage and related electrical parameters. Finally, an electric thermal coupling finite element model is established to analyze its discharge and tem-perature rise mechanism. The research results found that the infrared temperature rise characteristics and ultraviolet discharge characteristics of decay-like composite insulators can reflect their degradation status. As the testing distance increases, the measured infrared temperature rise gradually decreases. The distortion of dielectric parameters and the decrease in insulation resistance have caused partial discharge and abnormal temperature rise of decay-like insulators. In addition, compared to ultraviolet imaging detection, infrared temperature measurement can better reflect the internal defects of decay-like composite insulators and is less susceptible to interference from unrelated discharges around them.

At present, the identification of icing status of transmission line conductors is mainly manual. Although the mainstream method based on intelligent vision and UAV can solve the manual problem, the specific situation of conductor icing cannot be further mastered. Based on the information fusion of optical fiber sensor and continuous wavelet decomposition, the online sensing method of transmission line icing is studied. This method uses the transmission line conductor vibration and stress signal acquisition method based on distributed optical sensing technology. After the transmission line conductor vibration and stress signals are collected online by multiple optical fiber sensors, the fusion model based on Elman neural network is used to fuse the multiple optical fiber sensing information, and then the spectrum feature extraction method of optical fiber sensing signal based on continuous wavelet decomposition is used. The spectral characteristics of fused optical fiber sensing signals are extracted as diagnostic samples of the online perception method of conductor icing based on improved logical regression, and the binary classification method is used to identify whether there is icing problem on transmission line conductors online. In the experiment, this method can accurately perceive the online perception results of rime type icing, mixed rime type icing, wet snow type icing, and has the function of accurately sensing the icing status of transmission line conductors.

In order to solve the problem of frequent disconnection of carbon fiber conductors for large-capacity and long-distance transmission due to undetectable hidden defects,a detection method for hidden defects in multi-strand carbon fiber composite core conductors based on optical fiber sensing technology was proposed.The operating environment of the wire was established and the operating conditions were simulated.The time-domain reflection technology based on distributed fiber Brillouin scattering was adopted to detect the temperature and strain distribution of carbon fiber wires,and the optical time-domain reflection technology was combined to detect the loss of optical fibers in carbon fiber wires.Comprehensive comparative analysis was conducted to obtain signal feature quantities such as fiber temperature,strain and loss that could characterize hidden defects in multi-strand carbon fibers,and a neural network model was constructed with each signal feature quantity as input to the model.Through model training,the various weight coefficients within the model were determined,enabling it to effectively detect hidden defects in multi-strand carbon fiber composite core wires.The experimental results show that this method can effectively obtain signal feature quantities of various types of fiber optic and can accurately detect various hidden defects in wires,which has important practical application values.

In an effort to overcome the shortcomings of transmittal line heat mutation detection, such as the need for long-term preset external power supply and susceptibility to electromagnetic interference, we study the online detection of heat mutation of dispersed transmittal conductor based on staple optic sensing technique and correction of sensor prediction bias, which solves the issue of cross allergy between heat and damage. Based on the staple optic sensing technique, the staple optic transducer is designed and the Brillouin rate divert of the dispersed transmittal line is calculated; on the basis of the relationship between the Brillouin rate divert and the heat, the heat measurement result of the dispersed transmittal line is obtained; in the radial basis function meshwork, the heat measurement result is inputted, the heat measurement deviation of the staple optic transducer is predicted, and the prediction deviation is corrected to get the corrected heat measurement result; by comparing the current heat measurement result with the historical heat data, the heat measurement result of the staple optic transducer is predicted. By comparing the current heat measurement outcome with the historical heat data, the heat of the dispersed transmittal line is detected online, and an alarm is issued when the heat morph exceeds the preset threshold value. Experiments have proved that: the method can availably calculate the Brillouin rate divert of dispersed transmittal conductors and complete the heat measurement of transmittal conductors; the method can availably correct the prediction deviation of transmittal conductor heat and improve the exact of heat measurement; the method can availably detect the heat mutation of dispersed transmittal conductors online, and the detection exact is high.

The existing long-distance transmission line perception mainly focuses on the measurement and analysis of electrical parameters. When the line is subject to wind vibration, icing or galloping, the changes of electrical parameters are not obvious and difficult to capture, resulting in poor performance of long-distance transmission line fault state perception. In this regard, the long-distance transmission line condition sensing based on distributed optical fiber sensing technology is studied. This method designs corresponding sensing methods for four working conditions: using the back Brillouin scattering sensor and phase sensitive Rayleigh scattering sensor in the optical fiber sensing technology to form a multi parameter distributed optical fiber sensing device, which is used to sense the surface temperature, vibration, strain and other data of the long-distance transmission line; By analyzing the linear relationship between fiber Brillouin frequency shift and Brillouin power and fiber strain and temperature, the sensing results of icing thickness of long-distance transmission lines are obtained; By calculating the amplitude and phase information of the detection signal, the sensing results of long-distance transmission line vibration are obtained; By calculating the time difference of polarization mutation signal at both ends of long-distance transmission line, combined with the propagation speed of optical signal and the length of long-distance transmission line, the perception result of lightning fault location of long-distance transmission line can be obtained. The experimental results show that this method can more accurately collect the real-time operation data of long-distance transmission lines, and can effectively perceive the galloping, wind vibration and lightning fault location of long-distance transmission lines.

As the mainstream congestion control in Named Data Networking (NDN), the hybrid control mechanism integrates the advantages of consumer and router control mechanisms. However, The concurrent control by both consumers and routers may results in degraded data transmission performance. Therefore, we propose a novel hybrid congestion control scheme for NDN, called ndnSieve. By using the characteristics of Software Defined Network (SDN) that can achieve global network information acquisition as well as global resource scheduling, ndnSieve manages to invoke consumer and router control mechanisms based on different congestion states in the network respectively and achieves the synergy between two kinds of mechanisms. The results of experiment demonstrate that, compared with existing works, ndnSieve has the lowest average round-trip time, relatively high level of throughput and fairness, effectively improving the Quality of Service (QoS) of the network.

A method for identifying and measuring the hidden defects of optical cables based on Brillouin optic time domain reflectometer(BOTDR)distributed detection technology and demodulated signals was proposed to identify and measure the hidden defects of optical cables and ensure the safe operation of multi-strand carbon fiber optic cables used in projects such as capacity expansion and large span.In the production stage,the optical fiber was embedded in the composite core of multi-strand carbon fiber cable as a sensor.According to the principle of BOTDR technology and optic time domain reflectometer(OTDR)technology,a distributed sensing system for the detection of the hidden defects of carbon fiber cable was constructed.The hidden defects and position distribution of carbon fiber cable were analyzed in a multi-dimensional way by using the high-precision sensing of the optical fiber on temperature,stress and propagation loss,which realized hidden defect identification of optical cable.The Morlet wavelet was used to demodulate Brillouin scattering signal,extract envelope information and remove signal noise.Levenberg-Marquardt algorithm was used to fit Brillouin scattering spectrum data,accurately estimate the optimal Brillouin frequency shift parameter,and improve the overall defect recognition accuracy.The experimental results show that this method can accurately characterize the hidden defects of optical cable,realize the fast and effective identification of hidden defects of multi-strand carbon fiber cable,and promote the better application of carbon fiber cable in capacity expansion,large span and other projects.

Low-pressure water mist fire extinguishing systems are a cost-effective and highly reliable option for fire protection. However, they have not yet seen widespread use in urban underground utility tunnels. To validate the fire extinguishing effectiveness of the system in cable fires within urban utility tunnels and to identify the key factors influencing its efficiency, a scaled-down test platform for low-pressure water mist fire extinguishing in utility tunnels was constructed, and a series of fire extinguishing tests was conducted. The test results demonstrate that low-pressure water mist can rapidly and effectively extinguish cable fires in utility tunnels, with the quickest fire extinguishing time of 7 s. Within 50 s of activating the system, the internal temperature of the tunnel can be reduced from 650 °C to 40 °C. Among the influencing factors, the pressure and nozzle flow coefficient have a significant impact on the fire extinguishing efficiency, while nozzle spacing has a relatively smaller effect. Thus, when the nozzle spacing meets the requirement of “no dead zones”, priority should be given to increasing the pressure and nozzle flow coefficient.

The overhead conductors prepared by the traditional composite overhead conductor preparation method have low strength and poor arc sag characteristics, so we propose the preparation and nondestructive inspection method for the overhead conductors with multi-core rod thermoplastic carbon fiber composites. The composition of the overhead conductor is planned and designed, and the experimental equipment is used to prepare the overhead conductor, and the static mechanical properties and apparent quality of the prepared conductor are tested. In the experiments, the proposed method was verified for the preparation effect. The analysis of the experimental results shows that the composite overhead conductor prepared by the proposed method has a smooth thermal expansion curve and excellent arc sag characteristics.

为了研究射流水柱与低温氮气对由穿刺引发的锂离子电池热失控火灾的防控效果,开展了不同灭火剂种类(射流水柱与低温氮气)及不同灭火剂作用时间下的锂离子电池火灾灭火试验.研究结果表明:射流水柱灭火剂可用作扑灭锂离子电池火灾,但无法彻底阻断内部反应的进行,需较长时间持续释放作用以免发生复燃.相同作用时间内低温氮气无法持续有效地对电池进行降温,且作用期间电池存在较大复燃风险,针对锂离子电池火灾适用性较差.

Carbon fiber composite core wire in the carbon fiber core rod bending strength is low, easy to break, and thus affects the detection effect. In this regard, it is proposed to consider the bending performance of carbon fiber composite core overhead wire intrinsic defects fiber detection method. The overhead wire is X-ray scanned, and the image is bent compensated by the filtering algorithm. The image is reconstructed using an iterative reconstruction algorithm, and the Tamura texture feature operator is used to extract the roughness feature parameters in the texture feature enhancement map of each conductor to achieve the identification of defects. In the experiments, the proposed method is verified for detection accuracy. The analysis of the experimental results shows that the proposed method has a high correct defect recognition rate and has a more excellent detection accuracy when the proposed method is used to detect the inherent defects of overhead conductors.

The metal vapor arc plasma composition generated in the vacuum interrupter during the high current fault breaking process of vacuum circuit breakers is closely related to the characteristics of electrode materials. For analyzing the effect of electrode material on transport behavior of the metal vapor particle, the CuCr electrode of vacuum circuit breakers is taken as the research object. By establishing a microscopic NLTE Eindhoven model, the variation of particle composition and transport parameters of the arc plasma for CuCr alloy at different ratios are obtained and illustrated.

针对系统接线方式和线路分布电容影响导致柔性直流配电网故障辨识困难的问题,在对传统电流差动保护在柔性直流配电网中的适用性分析基础上,利用线路贝瑞隆模型推得故障点电流与直流线路两端差电流之间的关系.进一步地,提出具有线路分布电容电流补偿的新型电流差动保护方案,解决对称单极接线方式下故障特征微弱、分布电容电流影响大带来的故障辨识难题.最后,基于PSCAD/EMTDC仿真平台,建立柔性直流配电网模型,通过仿真分析验证所提出的电流差动保护方案的可行性和适用性.

The bolt connection looseness fault seriously affects the normal operation of the iron tower.It is very necessary to detect the bolt connection looseness fault of the iron tower.In this paper, a complete loosening detection method of tower bolts based on wavelet packet energy spectrum is proposed.Firstly, the vibration signals of the transmission tower before and after the bolt is completely loosened are measured by the pulse excitation method, and the vibration signals of the tower component where the excitation point is locatedand the vibration signals of the tower componentwhich was connected by bolt are obtained respectively.Then the wavelet packet is used to decompose the initial signal, the energy spectrum of each frequency band is found out by using the method of energy feature extraction.Finally, the change rule of wavelet packet energy spectrum of the two connected tower materials after the bolts are loosened is given, and the complete looseness detection rules of tower bolts based on wavelet packet energy spectrum is gotten.

Abstract Smart Grid, as a promising future architecture of Power Grid, its server mobility management is one of the important research contents in communication. Once the server moves, the routing table of some nodes will be invalid. As a result, the mobile server cannot be routed, which interrupts the requests of users and reduces the quality of network service. To solve the above problems, a mobility support mechanism based on the dynamic forwarding is pro-posed to ensure the stability of network. This mechanism updates the for-warding state on the router content plane by dynamically tracking the server’s location to reduce the unreachability of content during server movement. The simulation results show that DoM-FP can fully support server mobility. In the speed range of 0–30 m/s, the average packet loss rate caused by the mobile server is 8.1%, and the average retrieval delay is stable at 287.3ms. Addition-ally, the average additional consumption required to support server mobility is 0.35 packet/s.

为了解决锂离子电池在储存、运输中的失火难题,提出采用低温控制预防锂离子电池热失控的方法,并开展了低温冷却作用下三元锂离子电池热失控试验.研究结果表明:低温冷却能够通过降低锂离子电池内部反应活性,削弱锂离子电池热失控后的能量释放,进而阻断电池组间的热失控链式传播;锂离子电池的温度越低,电池越难发生热失控,当温度降至-30 ℃以下时,被直接穿刺的电池也不会发生热失控;由于低温的影响,电池内部材料活性降低,电池内部的化学反应受到限制,电池在试验后的质量损失和释放的CO气体体积分数显著降低.

阀控式铅酸蓄电池(VRLA)作为变电站备用直流电源时,其大部分运行时间处于浮充备用状态.大量数据显示,在变电站中做备用电源使用的一部分VRLA浮充寿命为6年左右,远低于10～12年的设计寿命.VRLA的提前失效,严重影响着变电站的正常安全运行.从变电站工况下VRLA运行状态和运行特性出发,探究VRLA浮充寿命衰减机制;根据阿伦尼乌斯公式推演VRLA高温加速浮充耐久性试验内在机理,以此为基础拓展VRLA高温加速浮充耐久性试验方案;进行VRLA高温加速浮充耐久性试验,定义质量损失率、24 h开路电压(OCV)损失倍率和内阻增长倍率,探究质量、开路电压和内阻与VRLA浮充寿命衰减的关系.

为解决高铁无线网络的通信干扰问题,提升高铁通信的吞吐量和能量效率,提出了一种基于博弈论的双目标优化干扰算法.首先,通过获取非理想信道的相应预编码矩阵和干扰抑制矩阵,计算包括延迟和衰落的非理想信道状态信息,实现干扰信号的空间对齐.其次,基于系统总功率、信干噪比,建立了功率分配双目标最佳博弈模型,实现吞吐量和能效的双重优化,并采用最大信噪比的干扰对齐算法,通过迭代计算实现干扰管理优化.最后,基于Matlab仿真平台与传统的干扰优化算法进行对比分析.实验结果表明,当信干噪比为30 dB、列车运行速度为300 km/h时,所提算法的吞吐量增加48.95％,能量效率增加53.02％,误码率减少14.37％;当信干噪比为30 dB、轨旁设备数量为5时,所提算法的吞吐量达到88.03％,能量效率达到71.58％;与其他算法相比,所提算法在系统吞吐量、能量效率和传输可靠性方面均具有显著优势.

为了提高双酚A环氧树脂(DGEBA)的综合性能,采用脂环族环氧树脂共混改性双酚A环氧树脂,并对共混体系的热、力学和电气性能进行综合分析.结果表明:当脂环族环氧树脂2021P的质量分数为10％时,共混体系的热-力-电综合性能较好,相比于纯双酚A环氧树脂,此时共混体系的玻璃化转变温度升高了3.18％,弯曲强度和拉伸强度分别提高了3.95％和4.65％,泄漏电流降低了6.03％,介质损耗因数减小了24.25％,工频电气强度提高了7.16％.