Based on a lot of measurement and analysis,this paper find that the unbalanced nature of 35 kV grids due to unsymmetrical capacitance values gives difficulty in neutral point operation in mountainous area.Improving co...Based on a lot of measurement and analysis,this paper find that the unbalanced nature of 35 kV grids due to unsymmetrical capacitance values gives difficulty in neutral point operation in mountainous area.Improving compensation of Petersen coil can rectify imbalance of voltage but bring up new problem that Petersen coil can not extinguish grounding arc effectively in fault.To put down contradiction mentioned above,this paper proposes a combination operation for neutral point of 35 kV grids as neutral point insulated in routine operation and grounding through Petersen coil in fault,then EMTP simulation is carried out.Simulation indicates that new neutral operation method can improve lightning withstand level and decrease trip-out rate of grids.展开更多
采用扫描叶片并结合Photoshop程序的数字图像处理技术测定油梨(Persea Americana Mill)叶面积,与传统的称重法和方格法进行比较。结果表明,称重法、方格法测得的叶面积与数字图像处理法测得的叶面积之间构成一元线性回归方程,相关系数r...采用扫描叶片并结合Photoshop程序的数字图像处理技术测定油梨(Persea Americana Mill)叶面积,与传统的称重法和方格法进行比较。结果表明,称重法、方格法测得的叶面积与数字图像处理法测得的叶面积之间构成一元线性回归方程,相关系数r分别为0.9984、0.9992,均达到极显著相关。这说明了数字图像处理技术测定油梨叶面积是可行的。与传统2种方法比较,数字图像处理技术具有速度快、精度高、非破坏性测量等的优点,尤其适合测量残缺不全的叶片。展开更多
基金Project Supported by Natural Science Foundation of CQ CSTC （ 2005BA6021 ）.
文摘Based on a lot of measurement and analysis,this paper find that the unbalanced nature of 35 kV grids due to unsymmetrical capacitance values gives difficulty in neutral point operation in mountainous area.Improving compensation of Petersen coil can rectify imbalance of voltage but bring up new problem that Petersen coil can not extinguish grounding arc effectively in fault.To put down contradiction mentioned above,this paper proposes a combination operation for neutral point of 35 kV grids as neutral point insulated in routine operation and grounding through Petersen coil in fault,then EMTP simulation is carried out.Simulation indicates that new neutral operation method can improve lightning withstand level and decrease trip-out rate of grids.
文摘采用扫描叶片并结合Photoshop程序的数字图像处理技术测定油梨(Persea Americana Mill)叶面积,与传统的称重法和方格法进行比较。结果表明,称重法、方格法测得的叶面积与数字图像处理法测得的叶面积之间构成一元线性回归方程,相关系数r分别为0.9984、0.9992,均达到极显著相关。这说明了数字图像处理技术测定油梨叶面积是可行的。与传统2种方法比较,数字图像处理技术具有速度快、精度高、非破坏性测量等的优点,尤其适合测量残缺不全的叶片。
