Process Analysis of Double Circuit Transmission Line Trip-out on the Same Tower Due to Lightning

In recent years,several failures of double circuit transmission line on the same tower due to lightning were happened in Beijing power grid.Although it can be reclosed successful,the lightning strike caused a grave threat to the power grid security.The cause of the accident and the accident process were studied for the sake of further understanding of the impact of lightning on power grid.As an example,110 kV double circuit transmission line(Xilong-line) was analyzed.At first,the system topology was given.Through the analysis on relay protection actions and the fault recorder data,over voltage on the insulator strings was calculated.Based on the analysis and the calculation,accident cause and the process were presented respectively.Secondly,it comes to the conclusion that the lightning failure was caused by counterattack.The wave of the lightning over voltage would spread to the not grounded neutral point of the transformers,and make the neutral protective gap breakdown,then cause freewheeling with the frequency of 50 Hz.As results of the relay protection,the double circuit transmission line all tripped out.Finally,the causes of the accident were proposed that included terrain features,large corner towers,strong thunderstorm weather and poor grounded contact of the tower.

Study of Lightning Damage Risk Assessment Method for Power Grid

Based on the idea of risk evaluation, the existing lightning damage risk assessment methods are reviewed and summarized in this paper. And the power grid lightning damage risk assessment system is established on the basis of lightning flashover risk evaluation methodology for transmission lines, and adopts the improved Analytic Hierarchy Process as the core algorithm. It can comprehensively evaluate the risk for transmission lines of regional grid, various sections of a line and each tower of the section, considering much more impact factors, including the running time of line, importance of grades, equipment damage, and the success rate of lightning stroke reclosing and so on. According to the calculation results of the risk assessment of the analytic hierarchy process and lightning flashover risk evaluation, the principles and methods of grade classification for power grid lightning damage risk map are studied, and give typical examples in the paper. It can describe the lightning withstanding ability much more scientifically and provide important references for the manage department of power system.

激活大麻素受体2可减轻实验性脓毒症大鼠的急性肺损伤

目的探讨激活大麻素受体2(CB2)对大鼠脓毒症急性肺损伤的保护作用及机制。方法将48只SD大鼠随机分为对照组、模型组、CB2激动剂组和P38 MAPK抑制剂组(12只/组)。对照组腹腔注射生理盐水,其余3组均腹腔注射脂多糖造模6 h;CB2激动剂组在注射脂多糖前30 min腹腔注射CB2激动剂JWH133(3 mg/kg),P38 MAPK抑制剂组在CB2激动剂组基础上提前30 min腹腔注射P38 MAPK抑制剂SB203580(5 mg/kg)。观察和检测肺组织病理学、含水率、液体清除率、炎症因子的变化情况,肺组织CB2、紧密连接的基因及蛋白表达情况以及P38 MAPK磷酸化情况。结果与对照组相比,模型组大鼠的肺泡结构破坏严重,液体清除率、肺组织中CB2、occludin和ZO-1蛋白的mRNA及蛋白表达降低,肺组织含水率、P38 MAPK的磷酸化程度、肺灌洗液中TNF-α、IL-1β均增加,差异有统计学意义(P<0.05)。与模型组相比,CB2激动剂组肺泡形态有所恢复,但仍有炎性浸润,肺组织含水率、P38 MAPK磷酸化程度、肺灌洗液中TNF-α、IL-1β降低,液体清除率、肺组织CB2、occludin和ZO-1蛋白的mRNA及蛋白表达增加,差异均有统计学意义(P<0.05)。与CB2激动剂组相比,P38 MAPK抑制剂组肺泡结构有所恢复,肺组织P38 MAPK磷酸化程度、肺灌洗液中TNF-α、IL-1β水平降低,occludin、ZO-1蛋白表达增加,差异均有统计学意义(P<0.05),而CB2的mRNA及蛋白表达无变化(P>0.05)。结论CB2激活后可通过抑制P38 MAPK信号通路,降低肺组织炎症因子释放,促进紧密连接蛋白表达,对实验性脓毒症大鼠急性肺损伤起到保护作用。

±500kV直流输电线路耐雷性能研究

直流架空输电线路的耐雷特性不同于交流系统,特高压直流输电线路杆塔高、跨度大,且工作电压幅值、极性不变,使得雷击直流高压输电线路的概率增大,有必要对直流架空输电线路耐雷性能进行研究。针对近年来葛南±500 kV直流输电线路多发的雷击故障,以葛南±500 kV直流单、双回架空输电线路为工程背景,采用ATP-EMTP和电气几何模型法分别对线路的反击和绕击耐雷性能进行了仿真计算研究,并与交流输电线路耐雷性能进行了分析比较。研究表明:±500 kV直流输电线路的雷电绕击跳闸率远高于反击跳闸率;工作电压对雷电先导发展、建弧率以及导线绕击距的影响比交流更大,使得直流输电线路正极性导线的雷击跳闸率高于负极性。