Study On Temperature Field Distribution Simulation And On-line Monitoring System Of Power Cable

The service life of the cable is mainly decided by the aging degree of insulation material. The temperature of the insulating material is an important factor in determining the speed of aging. Ampacity is a fundamental parameter of the power cable, overload ampacity will cause overheat, whereas insufficient ampacity is a waste of cable ability. Meanwhile, real-time monitoring the running cables will be beneficial to the cable safety and reliable operation. Therefore, this paper presents detailed analysis of temperature field and ampacity of cables, and also discusses the cable joint temperature distribution. Then, it is helpful to develop an on-line monitor system for cable temperature to improve operational efficiency and safety of cables.Firstly, this paper introduces the XLPE power cable structures, clarifies the principle and position of cable heat generation. Heat transfer FEM analysis considers heat conduction, convection, radiation, which covers three basic principles of heat transfer and heat balance equation. The FEM solver works out a result with boundary condition added. In this paper, COMSOL Multiphysics finite element analysis software is used to calculate temperature distribution of four-loop cables in cable trench, and to calculate the cable Ampacity. Temperature field distribution figures out the hottest position of the cable trench and calculated ampacity of irregular cable trench laying is 22% lower than that of regular laying cable. Meanwhile, the more intensive layed cables are, the lower their ampacity is. Then, a thermal analysis of cable joints is performed. The results showed that core temperature of qualified cable joint is a little lower than those far from core. The result of cable joint temperature under the influence of contact resistance shows that the joint core temperature gradually increases as the contact resistance increases. Only if k?0.96, the cable joint can be safe and reliable running. By using finite element simulation to locate the overheated position of cable groups, it provides theoretical support for locating the temperature sensors' sites. Meanwhile, the simulation figured out the upper limit of the cable's skin temperature, it solves the problem to directly monitor the core temperature.Finally, this paper fabricates a cable trench multi-physics monitoring system. Temperature sensors are calibrated to insure the measurement accuracy. Zigbee and GPRS data transmission method are combined for data transfer, the master chip CC2530F256 is used for programming controlling, and system have the ability of real-time access through mobile phones with fault alarm. Equipment carried out a detailed simulation of laboratory experiments and demonstration package. Finally, the equipment has been installed in ZiShan cable trench line of Chongqing and run in a cable trench, detailed analysis of received data indicates that the system is working well to guarantee long-term stability and safety of power cable.