Study on the Calculation of Cable Emergency Current Capacity Based on Real-time Measurement Data

In actual operation, the cable may bear extra load due to other line faults within a certain time. This load is called the emergency Current Capacity, and this time period is called the emergency time. There are two main ways to solve the emergency Current Capacity using the thermal circuit. One is to take the surface temperature of the cable outer sheath as the boundary of the transient thermal circuit, without considering the influence of laying environment. The other is to use the environmental thermal parameters recommended by IEC standard. Since the actual environment along the cable is complex and changeable, and the environmental thermal parameters are time-varying, both methods will cause errors. In this paper, the environmental thermal parameters are calculated by using the data obtained from the real-time measurement, which is then substituted into the derived formula to obtain the emergency Current Capacity algorithm. The correctness of the algorithm is verified by comparing the results with the ones of FEA simulation and IEC. The results show that: the algorithm proposed in this paper is safe and more accurate. The effects of initial load and emergency time are also be analysed at the same time.