Numerical study of transient flow dynamics in a core-type transformer windings

摘要

The transient hydraulic behaviour in a given pass of a low voltage Core-type power transformer winding was simulated using Computational Fluid Dynamics in order to study and characterize the dynamic response of oil flow to a sinusoidal type perturbation on the oil inlet velocity. Different parameters were tested, namely the oil temperature, the oil inlet velocity and the duration of the sinusoidal perturbation.The dynamic friction factor was calculated as a function of the Reynolds number. For fast perturbations, the discrepancies between the calculated dynamic and the steady-state friction factor are observed only during the short-term period of the perturbation. For smooth and longer perturbations, the system slowly redistributes the oil flow through the radial channels and differences to initial steady-state are not as noticeable. Overall, the curve fit obtained for steady-state conditions is valid for transient conditions. Furthermore, the results show that, in order to develop a new Thermal Hydraulic Network Model (THNM) Dynamic simulator, only the hydraulic resistance needs to be considered.