The Behavior of Polyurethane Foam-Filled Glass-Fiber-Reinforced Polymer Crossarm Subjected to Lightning Transient Voltage

The demand for composite materials in high-voltage electrical insulation is escalating over the last decades. In the power system, the composite glass-fiber-reinforced polymer has been used as an alternative to wood and steel crossarm structures due to its superior properties. As a composite, the material is susceptible to multi-aging factors, one of which is the electrical stress caused by continuous and temporary overvoltage. In order to achieve a better insulation performance and higher life expectancy, the distribution of the stresses should firstly be studied and understood. This paper focuses on the simulation work to better understand the stress distribution of the polyurethane foam-filled glass-fiber-reinforced polymer crossarm due to the lightning transient injection. A finite-element-based simulation was carried out to investigate the behavior of the electric field and voltage distribution across the sample using an Ansys Maxwell 3D. Electrical stresses at both outer and inner surfaces of the crossarm during the peak of lightning were analyzed. Analyses on the electric field and potential distribution were performed at different parts of the crossarm and correlated to the physical characteristics and common discharge location observed during the experiment. The results of the electric field on the crossarm indicate that both the outer and internal parts of the crossarm were prone to high field stress.     

Lightning Does Strike Twice: A Fulminology Primer for Nurse Practitioners

Lightning strikes cause more fatalities in the United States than floods, tornadoes, or hurricanes, although 90% of victims survive. Lightning strikes can cause diverse and major health consequences for every organ system, resulting in cardiovascular, neurological, and mental health sequelae. Misinformation and a lack of understanding about lightning and the associated health risks are commonplace. Therefore, nurse practitioners have the opportunity to apply evidence-based knowledge in the care of lightning-strike victims, as well as educate all their patients on preventive measures.     

信息网络建设审的雷电防护对策

通过雷电损害的表现形式,分析了雷电损害入侵信息网络系统的途径,提出了信息网络系统建设在雷电防护工作中可能疏忽的问题,并给出对雷电损害的防护原则和解决方案。     

Case report of a 13-year-old struck by lightning

Lightning strikes kill 1,000 people per year worldwide. Cardiac arrests resulting from lightning strikes have good survival rates but there is a significant degree of morbidity amongst the survivors. This is the case report of a 13-year-old boy who had a cardiac arrest following a direct lightning strike, and his subsequent management.     

雷电击致小儿烧伤的探讨

目的探讨雷电击致小儿烧伤的原因。方法回顾分析我科近二十年来收治的8例雷电击致小儿烧伤的情况。结果小儿在野外突然遭雷击,逃脱能力太差。结论雷电击致小儿烧伤严重,完全可以预防,避免发生。     

Finite Element Analysis of Lightning Damage Factors Based on Carbon Fiber Reinforced Polymer

While carbon-fiber-reinforced polymers (CFRPs) are widely used in the aerospace industry, they are not able to disperse current from lightning strikes because their conductivity is relatively low compared to metallic materials. As such, the undispersed current can cause the vaporization or delamination of the composites, threatening aircraft safety. In this paper, finite element models of lightning damage to CFRPs were established using commercial finite element analysis software, Abaqus, with the user-defined subroutines USDFLD and HEAVEL. The influences of factors such as the structural geometry, laminate sequence, and intrinsic properties of CFRPs on the degree of damage to the composites are further discussed. The results showed that when a current from lightning is applied to the CFRP surface, it mainly disperses along the fiber direction in the outermost layer. As the length of the CFRP increases, the injected current has a longer residence time in the material due to the increased current exporting distance. Consequently, larger amounts of current accumulate on the surface, eventually leading to more severe damage to the CFRP. This damage can be alleviated by increasing the thickness of the CFRP, as the greater overall resistance makes the CFRP a better insulator against the imposed current. This study also found that the damaged area increased as the angle between the first two layers increased, whereas the depth of the damage decreased due to the current dispersion between the first two layers. The analysis of the electrical conductivity of the composite suggested that damage in the fiber direction will be markedly reduced if the conductivity in the vertical fiber direction increases approximately up to the conductivity of the fiber direction. Moreover, increasing the thermal conductivity along the fiber direction will accelerate the heat dissipation process after the lightning strike, but the influence of the improved thermal conductivity on the extent of the lightning damage is less significant than that of the electrical conductivity.     

Electrical Performance of Polymer-Insulated Rail Brackets of DC Transit Subjected to Lightning Induced Overvoltage

The fourth rail transit is an interesting topic to be shared and accessed by the community within that area of expertise. Several ongoing works are currently being conducted especially in the aspects of system technical performances including the rail bracket component and the sensitivity analyses on the various rail designs. Furthermore, the lightning surge study on railway electrification is significant due to the fact that only a handful of publications are available in this regard, especially on the fourth rail transit. For this reason, this paper presents a study on the electrical performance of a fourth rail Direct Current (DC) urban transit affected by an indirect lightning strike. The indirect lightning strike was modelled by means of the Rusck model and the sum of two Heidler functions. The simulations were carried out using the EMTP-RV software which included the performance comparison of polymer-insulated rail brackets, namely the Cast Epoxy (CE), the Cycloaliphatic Epoxy A (CEA), and the Glass Reinforced Plastic (GRP) together with the station arresters when subjected by 30 kA (5/80 µs) and 90 kA (9/200 µs) lightning currents. The results obtained demonstrated that the GRP material has been able to slightly lower its induced overvoltage as compared to other materials, especially for the case of 90 kA (9/200 µs), and thus serves better coordination with the station arresters. This improvement has also reflected on the recorded residual voltage and energy absorption capacity of the arrester, respectively.     

应用交腿皮瓣修复足踝关节严重损伤

目的　观察应用交腿腓肠肌肌皮瓣修复足、踝关节严重损伤的效果。方法　选取 2 0 0 2年 8月— 2 0 0 3年 11月我院 5例足严重损伤病人 ,均为男性 ,年龄 2 6～ 47岁。高压电伤 1例 ,为接触 3 5万V高压电致伤 ;热压伤 3例 ;重物砸伤 1例。设计对侧小腿腓肠肌内侧头肌皮瓣 ,皮瓣基部位于小腿后上方 ,后缘位于小腿后正中线 ,前缘位于大隐静脉内侧 ,皮瓣大小为 3 0cm× 11 5cm～ 18cm× 7cm。保护小隐静脉及腓肠神经 ,找到腓肠动脉进入腓肠肌的点 ,并分出腓肠肌外侧皮瓣的营养动脉 ,加以保护 ,切取皮瓣。行创面清创 ,尽量清除坏死组织 ,保留间生态组织 ,对于大血管周围坏死组织可予以适当保留 ,以过氧化氢溶液及 0 1%苯扎溴铵溶液反复清洗创面 ,彻底止血 ,将皮瓣移植缝合于创面 ,皮瓣下放置橡皮引流条 ,双下肢行石膏托固定。结果　所作 5个腓肠肌内侧头肌皮瓣及 1个腓肠肌外侧头肌皮瓣均顺利成活 ,创面修复满意。结论　腓肠肌肌皮瓣作为交腿应用具有可供切取的皮瓣面积大 ,应用灵活、有足够长的蒂 ,可再利用、抗感染能力强、容易固定、操作简便 ,成功率高、供区功能不受影响的优点