Dynamic thermal analysis for underground cables under continuously fluctuant load considering time-varying van wormer coefficient

Abstract With the extensive integration of renewable energy sources in power system, the fluctuation characteristics of transmission and distribution network load have been further strengthened. However, for the power cable widely used in power system, its dynamic thermal behavior under continuously fluctuant load cannot be well modeled by the IEC method. It has not been sufficiently addressed in the literatures either. In this paper, the variation of the time-dependent Van Wormer coefficient and the error cumulative phenomenon of adopting the constant Van Wormer coefficient in conventional methods (including the IEC 60853-2 and the classical thermo-electric equivalent method) under continuously fluctuant cable load are discussed. Moreover, several different modification ways on the lumped thermal model of cable insulation to mitigate the possible error cumulative phenomenon are presented. The superiority of the modified methods compared with the conventional methods is verified by the real cable experiments. The results show that the modified methods can better reflect the cable's real thermal behavior under continuously fluctuant load. The modified methods are instructive for maximizing cable utilization while still ensuring cable reliability, which can be easy to be integrated into the existing real-time cable thermal rating system.