The ultrasonic wave velocities of Japanese cedar columns were measured using a non-contact method. An air-coupled ultrasonic wave was propagated through the axial and lateral directions of wood. The velocities in the ...The ultrasonic wave velocities of Japanese cedar columns were measured using a non-contact method. An air-coupled ultrasonic wave was propagated through the axial and lateral directions of wood. The velocities in the axial direction (V<sub>L</sub>) showed the minimum values around the pith. The averaged V<sub>L</sub> increased from 3600 m/s towards the outside of measurement area and attained the maximum values (=4010 m/s). The velocities in the lateral direction (V<sub>RT </sub>) showed no tendency among measurement points. The averaged V<sub>RT </sub> was 1450 m/s. The velocities obtained using the non-contact method showed a significant positive relationship with those obtained using the contact method. The averaged ratio of V<sub>L</sub> to V<sub>RT </sub> was measured to be approximately 2.2 to 2.8. These ratios were in agreement with those from a contact method. These findings suggest that it is possible to measure the velocity in Japanese cedar columns with the non-contact method by using air-coupled ultrasonics.展开更多
特高压直流GIL运行可靠性取决于内绝缘设计的可靠性。此外,导电元件直流电流密度的取值、弹簧触头的定位设计、GIL各元件中的绝缘件与金具连接处的楔形气隙的处理以及母线中支撑件的结构设计细节,都会对产品运行可靠性产生重大影响,不...特高压直流GIL运行可靠性取决于内绝缘设计的可靠性。此外,导电元件直流电流密度的取值、弹簧触头的定位设计、GIL各元件中的绝缘件与金具连接处的楔形气隙的处理以及母线中支撑件的结构设计细节,都会对产品运行可靠性产生重大影响,不能忽视。对于运行环境十分严酷的UHV DC GIL为保证内绝缘工作可靠性和减少气体维护工作量,文中还提出了高气密性结构设计。为适应-50℃低温运行要求,产品选用了液化温度很低的N_(2)/SF_(6)混合气体,对两种气体的配比,压力特性和绝缘特性进行了讨论与计算。还有产品的局放、气体密度及微水含量的监视系统的可靠性设计,都会对产品运行可靠性产生直接影响。文中对上述问题的研究成果作了介绍,可供高压直流产品设计使用。对其中未解的新技术如基于冷镜露点测试原理、微机电技术制作的智能气体湿度和密度监测装置、高压直流复合绝缘套管伞面局放起始场强提出了研究方案。文中提出的诸多GIL运行可靠性设计要点,对于其他超/特高压直流气体绝缘电器可参考选用。展开更多
文摘The ultrasonic wave velocities of Japanese cedar columns were measured using a non-contact method. An air-coupled ultrasonic wave was propagated through the axial and lateral directions of wood. The velocities in the axial direction (V<sub>L</sub>) showed the minimum values around the pith. The averaged V<sub>L</sub> increased from 3600 m/s towards the outside of measurement area and attained the maximum values (=4010 m/s). The velocities in the lateral direction (V<sub>RT </sub>) showed no tendency among measurement points. The averaged V<sub>RT </sub> was 1450 m/s. The velocities obtained using the non-contact method showed a significant positive relationship with those obtained using the contact method. The averaged ratio of V<sub>L</sub> to V<sub>RT </sub> was measured to be approximately 2.2 to 2.8. These ratios were in agreement with those from a contact method. These findings suggest that it is possible to measure the velocity in Japanese cedar columns with the non-contact method by using air-coupled ultrasonics.
文摘特高压直流GIL运行可靠性取决于内绝缘设计的可靠性。此外,导电元件直流电流密度的取值、弹簧触头的定位设计、GIL各元件中的绝缘件与金具连接处的楔形气隙的处理以及母线中支撑件的结构设计细节,都会对产品运行可靠性产生重大影响,不能忽视。对于运行环境十分严酷的UHV DC GIL为保证内绝缘工作可靠性和减少气体维护工作量,文中还提出了高气密性结构设计。为适应-50℃低温运行要求,产品选用了液化温度很低的N_(2)/SF_(6)混合气体,对两种气体的配比,压力特性和绝缘特性进行了讨论与计算。还有产品的局放、气体密度及微水含量的监视系统的可靠性设计,都会对产品运行可靠性产生直接影响。文中对上述问题的研究成果作了介绍,可供高压直流产品设计使用。对其中未解的新技术如基于冷镜露点测试原理、微机电技术制作的智能气体湿度和密度监测装置、高压直流复合绝缘套管伞面局放起始场强提出了研究方案。文中提出的诸多GIL运行可靠性设计要点,对于其他超/特高压直流气体绝缘电器可参考选用。
