Research Of Composite Submarine Cable Online Monitoring System

In recent years, with the growth of the number of offshore drilling platforms, the number of submarine cable quantity is increasing. In 2012, the area of Bohai sea has 77 submarine cables whose length are about 447 km. With the needs of oil field's development and the power plant grid work, more submarine cable will be applied. Oil platform connected to grid by submarine cable grid, the stable operation of the cable not only relates to the production of wellhead platforms, but also is related to the reliable operation of the power grid. Due to the special operation environment of submarine cables, regular checkingmanagement cannot be implemented and saftymanagement measures are insufficient. Once the accident happens, the losses will be huge. So it is significant tomonitor the increasing submarine power cables online for guaranteeing the normal operation of the oil platform.When producing the submarine cable, manufacturers retain more than 20% of the redundant fiber at least. So by using redundant optical fiber and the principle of fiber Brillouin scattering, the temperature and stress changes of submarine cable can be monitored. This use of the optical fiber in the composite submarine cable, without changing the structure of the existing submarine cable and without increasing sensors, achieves continuous real-time monitoring online, which make us in advance find the fault hidden trouble and trend of the submarine cable and then prevent the passive impact caused by sudden accidents.The paper will first propose an overall scheme of composite submarine cable online monitoring system and introduce the parameter's performance of the system's hardware, and then put forward design requirements and thoughts of PC software. After that, the paper will elaborate the theory of Brillouin scattering which is applied to the submarine cable temperature monitoring and the deformation monitoring. Next, by using the theory of finite element, submarine cable temperature field and stress field models are established in ANSYS environment. In the end, the paper will calculate each phase and threshold of the system by correcting the parameters in the operation environment of simulated experiment.On this basic, the paper provides the overall design of the software according to system's requirements with the development and implementation. The software is developed on the basis of Lab Windows/CVI to complete the functions of data acquisition, processing, storage, display and so on. In the data acquisition and processing module, multi-threading technology based on thread pools and data protection mechanisms based on thread safe queues with thread lock are used to improve response speed and meet real-time requirements. A custom data transmission format and Modbus TCP communication protocol are used to ensure the reliability of data transmission, which effectively solve the problem of data transmission. A quick query to achieve the mapping from optical fiber temperature data to the cable conductor temperature is designed with database technology. The analysis algorithm of submarine cable security status is studied and implemented in this paper, while some key problems such as data storage and history inquiries are solved.At present, the system has been put into operation in Suizhong36-1 APP to Lvda5-2 platforms and the monitoring data has been continuously obtained. The paper will analyze the measured data of the monitoring system to prove the feasibility of the project.