Studying On The On-line Temperature Monitoring System For Power Cable

Purpose of on-line monitoring system for power cable is to ensure that the cables are operated at a temperature range within their specified parameters and than they do not undergo excessive heating and premature aging. The system performs real-time calculations of conductor temperature based on cable installation, cable surface temperatures, load current measurements and a realistic knowledge of the thermal environment of a cable. The real-time monitoring will enable system operators to handle emergency situations much more effectively, to reduce the misoperation of local switches and to adjust ampacity of cable to allowable ampacity rating under reasonable allowed safety margins.Firstly, the structure of XLPE cable is studied to develop the formula of effective resistance, dielectric loss, metal sheathing loss, shield loss and the thermal resistance of cable. And then the paper analyses the calculation of the current-carrying capability, or ampacity, of electric power cables and the calculations of conductor temperature in real-time of steady state and transients based on a ladder thermal network of cable. Secondly, according to actual condition in tunnel, scheme of using wireless data communication system for the data acquisition system of the measured sheath or surface temperature of a cable is adopted and temperature sensing equipment is designed .Finally, software design of on-line temperature monitoring and predicting system for power cable based on the real-time algorithm is developed and system simulation is operated.According to the requirement of the function of on-line temperature monitoring system for power cable, the whole system design is divided into two function modules and modules are designed separately. Finally, each function module is integrated into the whole system.At the end of this thesis, the results of system simulation show that the percentage error of this device is less than 5%. Functions for real time monitoring, ampacity rating, temperature predicting is implemented and the expected requirement of the project is satisfied.