Study On The Transient-State Temperature Field And Ampacity Real-Time Caculation Method Of Single Core Cable

Power cable is one of the key power transmission equipments. Cable rated current is based on conservative parameters, so we can not take full advantage of the power cable transmission capacity.In order to exploit the potential transmission capacity, power cable real-time ampacity monitoring is carried out. Power cable ampacity real-time monitoring system provides the information of utilization load ability, and helps staff to make more reasonable decisions scheduling the load distribution in the future.The system is conducive to optimize the allocation of power cable load. This paper has studied on the relationship among cable surface temperature, conductor temperature and the ampacity. Based on the ampacity calculation method summed up, single-core cable surface temperature monitoring system on-line has been designed. This paper analyzes the transient temperature field and promises the real-time calculation method of single-core cable ampacity.Single-core cable ampacity is real-time calculated with online temperature information and load datas. According to the functional requirements of temperature measurement, a cable surface temperature on-line monitoring system has been designed. The hardware circuit design and sub-station software design have been completed based on the general framework and practical application. Combined with cable surface temperature monitoring system, the experimental system has been designed to verify single core power cable ampacity calculation method on-line. Some measures related power and temperature sensor installation can reduce systematic errors.In response to the actual situation of ambient temperature and load greatly changing, real-time ampacity calculation should base on the transient temperature field. The finite element equation of single-core cable transient temperature field is stabled. The temperature distribution can be acquired any time (especially conductor temperature) with the equation; Refer to cable buried in the underground, overhead or conduit covered up, this paper has brought forward the real-time ampacity calculation method. By analysing equal thermal circuit, this paper indirectly identify external resistance, with surface temperature, ambient temperature and real-time load. The method overcomes the problem, which the external thermal resistance (soil conductivity) is difficult to accurately determine in the traditional calculation. The overhead cable ampacity experiment is carried out by changing the load and ambient temperature. Contrasting experimental datas with simulation results, the error in the calculation is within 5 percent. The results verify the validity and accuracy of the calculation method.