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同频同相交流耐压试验技术因无需母线全停,现已在220 kV GIS设备检修或扩建后的绝缘性能试验中得到了广泛应用。然而,110 kV变电站普遍采用三相共筒式GIS设备,由于相间紧凑布置,在对三工位隔离开关进行耐压试验时,隔离开关断口击穿风险较大,这将给系统供电可靠性带来极大影响。使用EMTP-ATP仿真软件搭建了同频同相交流耐压试验中110 kV GIS设备隔离断口击穿仿真模型,获得了同相击穿和异相击穿的故障电压及电流特性,分析了加装保护电阻对击穿特性的影响规律,给出了击穿特性抑制措施建议,为同频同相技术在110 kV GIS设备交流耐压试验中的应用提供了指导。 相似文献
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基于灰度级模糊C均值图像分割算法具有分割速度快的优势。由于无损检测图像中背景类和目标类差异较大,该算法不能有效地将目标分割出来,故提出改进的基于灰度级的模糊C均值算法。构建了一种与类大小反向相关的类贡献抑制因子表达式,将之融入目标函数后能够降低较大类对目标函数的贡献,这可避免较小类的聚类中心受较大类的影响而靠近较大类的聚类中心。最小化新的目标函数可得新形式的隶属度和聚类中心表征形式。采用类大小差异较大的无损检测图像进行试验,结果显示本文算法得到的分割图像视觉效果良好,而且指标G_mean也更高,进一步提升了基于灰度级模糊C均值算法适应能力。 相似文献
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The thermal properties of photonic crystal fiber(PCF) laser with 18 circularly distributed cores are investigated by using full-vector finite element method(FEM).The results show that the 18-core PCF has a more effective thermal dispersion construction compared with the single core PCF and 19-core PCF.In addition,the temperature distribution of 18-core PCF laser with different thermal loads is simulated.The results show that the core temperature approaches the fiber drawing value of 1800 K approximately when the thermal load is above 80 W/m which corresponds to the pumping power of 600 W approximately,while the coating temperature approaches the damage value of about 550 K when the thermal load is above 15 W/m which corresponds to the pumping power of 110 W approximately.Therefore the fiber cooling is necessary to achieve power scaling.Compared with other different cooling systems,the copper cooling scheme is found to be an effective method to reduce the thermal effects. 相似文献
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Research on the transverse mode competition in a Yb-doped 18-core photonic crystal fiber laser 下载免费PDF全文
A model based on propagation rate equations is built up for analyzing the multicore transverse mode gain distribution in an 18-core photonic crystal fiber(PCF)laser.The two kinds of feedback cavities are used for the fiber laser,which are the butt-contact mirror and the Talbot cavity.According to the model,the transverse mode competitions in different feedback cavities are simulated numerically.The results show that the Talbot cavity can improve in-phase supermode gain,while suppress other supermodes. 相似文献
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为掌握电缆水树老化程度对电缆主绝缘介电特性的影响规律,对交联聚乙烯(cross-linked polyethylene,XLPE)开展加速水树老化试验,以低密度聚乙烯为对照组,测量不同老化程度试样的介电常数(ε)、介质损耗因数(tanδ)、结晶度以及熔点等特征参量,并利用显微技术观测XLPE水树的生长特性。结果表明:XLPE材料的ε和低频下tanδ随水树老化程度加深而呈现增大的趋势。水树在发展过程中呈现放射状,且密集度不断增加。建立XLPE材料的tanδ宏观参量与微观水树老化发展的对应关系,可通过低频下电缆主绝缘材料XLPE的tanδ值评估电缆水树老化的严重程度。 相似文献