Monitoring The Operation Of Distribution Cable And Forecasting Its Ampacity Based On Optical Fiber Temperature Measurement

In the process of urbanization, crosslinked polyethylene cables are widely used, however, the contradiction between increasing power load and adding more cable lines becomes increasingly prominent. As is well known, ampacity reflects the power supply capacity of cable, but it is difficult to have a clear understanding of the ampacity of distribution cables in urban area because of cluster laying, diverse way of laying and complex external factors. It is helpful to master the condition of a running distribution cable line by using optical fiber temperature measurement system monitor conductor temperature of it. And on this basis forecasting the ampacity of distribution cable, improving the ampacity of existing cable is the best way to resolve the conflicts.In this paper, real-time three-core cable conductor temperature calculation software is developed after studying the method of computing transient conductor temperature by using skin temperature. In test site, periodic load temperature rise experiments of distribution cables are carried out in their typical laying way. By comparing the calculated values and experimental values the correctness of the software is verified. After using the certified software and optic fiber temperature measurement system to monitor operating temperature of 10 k V clusters laying distribution cable at a station in Guangzhou for a long time, the running status of clusters laying distribution cable is mastered. Monitoring results show that the operation environment and the load character have an impact on cable carrying capacity. Some cables are not really overloaded in truth, their current-carrying capacity can be further enhanced. To provide a basis for operating personnel, this paper presents a method to forecast continuous ampacity and emergency ampacity of running distribution cables based on the current situation. By evaluating on running cable, the current carrying capacity can be further improved while it is overloaded at present. It is suggested to reappraise the cable which is overload based on monitoring temperature. Emergency ampacity forecasting shows that the shorter emergency time is, the higher emergency ampacity will be. The emergency ampacity which is much higher than continuous ampacity can be used in emergency power supply but it will not affect the working life of cables.Monitoring distribution cables based on optic fiber temperature measurement system can make a clear understanding of running status of cables and then forecast ampacity. Adjusting load current according to its running status is helpful to improve transmission capacity of existing cable lines.