Analytic Approaches for the Transient Temperature Distribution in a Single Cable for Smart Fuses and Ampacity Derating Calculation

To protect cables from damage by too high temperatures, classically fuses are used. Those often lead to over-dimensioned cables due to their melting behaviour or simple tripping strategies. Therefore, smart fuses can be advantageous. Here, a more powerful control circuit can estimate the cable temperature and operate as switch, when the temperature exceeds a given limit. The control circuit needs to run a thermal simulation of the cable to be protected. Critical temperatures can be detected this way. Thermal cable models can be very complex and computationally intensive, especially when numerical methods are used. In this contribution, a new analytic approach for the transient axial temperature distribution along a single cable is presented. Using this solution, a significant reduction of the time needed for calculation is achieved.