Internal solitary waves(ISWs) contain great energy and have the characteristics of emergency and concealment. To avoid their damage to offshore engineering, a new generation of monitoring and early warning system for ...Internal solitary waves(ISWs) contain great energy and have the characteristics of emergency and concealment. To avoid their damage to offshore engineering, a new generation of monitoring and early warning system for ISWs was developed using technologies of double buoys monitoring, intelligent realtime data transmission, and automatic software identification. The system was applied to the second natural gas hydrates(NGHs) production test in the Shenhu Area, South China Sea(SCS) and successfully provided the early warning of ISWs for 173 days(from October 2019 to April 2020). The abrupt changes in the thrust force of the drilling platform under the attack of ISWs were consistent with the early warning information, proving the reliability of this system. A total of 93 ISWs were detected around the drilling platform. Most of them occurred during the spring tides in October–December 2019 and April 2020, while few of them occurred in winter. As suggested by the theoretical model, the full-depth structure of ISWs was a typical current profile of mode-1, and the velocities of wave-induced currents can reach 80 cm/s and30 cm/s, respectively, in the upper ocean and near the seabed. The ISWs may be primarily generated from the interactions between the topography and semidiurnal tides in the Luzon Strait, and then propagate westward to the drilling platform. This study could serve as an important reference for the early warning of ISWs for offshore engineering construction in the future.展开更多
正弦波调制全光纤电流互感器(fiber optical current transformer,FOCT)因具备动态范围大、不与一次主回路连接、绝缘性能好、无铁磁饱和等优点,成为特高压换流站重要的测量设备。但在实际运行过程中,FOCT故障率远高于电磁互感器,而光...正弦波调制全光纤电流互感器(fiber optical current transformer,FOCT)因具备动态范围大、不与一次主回路连接、绝缘性能好、无铁磁饱和等优点,成为特高压换流站重要的测量设备。但在实际运行过程中,FOCT故障率远高于电磁互感器,而光回路故障是最为常见的故障类型。针对此,首先建立FOCT数学模型,提出二次谐波、光强峰值、平均光强应作为重要监测量;在此基础上分析光回路故障对探测器输出信号的影响,提出基于驱动电流及探测器输出信号变化的光回路故障预警方法,通过阈值设置及平均光强趋势判断等辨识真实的光回路故障。最后开展现场试验验证,证明该预警方法的有效性。展开更多
基金funded by the Key Special Project for Introduced Talents Team of Southern Marine Science and Engineering Guangdong Laboratory (Guangzhou) (GML2019ZD0307)the Marine Geological Survey Program of China Geological Survey (DD20190218, DD20221706)+1 种基金the Key Program of Marine Economy Development Special Foundation of Department of Natural Resources of Guangdong Province (GDNRC [2020] 043)the National Natural Science Foundation of China (41806074, 41730528)。
文摘Internal solitary waves(ISWs) contain great energy and have the characteristics of emergency and concealment. To avoid their damage to offshore engineering, a new generation of monitoring and early warning system for ISWs was developed using technologies of double buoys monitoring, intelligent realtime data transmission, and automatic software identification. The system was applied to the second natural gas hydrates(NGHs) production test in the Shenhu Area, South China Sea(SCS) and successfully provided the early warning of ISWs for 173 days(from October 2019 to April 2020). The abrupt changes in the thrust force of the drilling platform under the attack of ISWs were consistent with the early warning information, proving the reliability of this system. A total of 93 ISWs were detected around the drilling platform. Most of them occurred during the spring tides in October–December 2019 and April 2020, while few of them occurred in winter. As suggested by the theoretical model, the full-depth structure of ISWs was a typical current profile of mode-1, and the velocities of wave-induced currents can reach 80 cm/s and30 cm/s, respectively, in the upper ocean and near the seabed. The ISWs may be primarily generated from the interactions between the topography and semidiurnal tides in the Luzon Strait, and then propagate westward to the drilling platform. This study could serve as an important reference for the early warning of ISWs for offshore engineering construction in the future.
文摘正弦波调制全光纤电流互感器(fiber optical current transformer,FOCT)因具备动态范围大、不与一次主回路连接、绝缘性能好、无铁磁饱和等优点,成为特高压换流站重要的测量设备。但在实际运行过程中,FOCT故障率远高于电磁互感器,而光回路故障是最为常见的故障类型。针对此,首先建立FOCT数学模型,提出二次谐波、光强峰值、平均光强应作为重要监测量;在此基础上分析光回路故障对探测器输出信号的影响,提出基于驱动电流及探测器输出信号变化的光回路故障预警方法,通过阈值设置及平均光强趋势判断等辨识真实的光回路故障。最后开展现场试验验证,证明该预警方法的有效性。
