Numerical analysis of the cold start of a distribution transformer filled with biodegradable oil

Resumo

This work presents a numerical analysis of the cold start of a distribution transformer filled with
biodegradable oil in order to obtain a detailed description of temperatures and velocities distributions inside the
transformer. When the transformer is placed in very extreme conditions, like in a wind farm with very low ambient
temperature, and is filled with biodegradable oil the pour point of the oil can be reached. This type of analysis
has not been necessary since mineral oils have very low pour point temperatures, below −40 °C, but in the case
of conventional sunflower oil can be −18 °C. When the transformer is started from a temperature near the pour

point the fluidity and hence the natural convection phenomena, which is the principal mechanism of the heat trans-
portation inside the transformer, can be dramatically reduced. This reduction can lead to a local increase in the oil

temperature, principally in the windings oil channels. In this work, several working temperatures are analyzed for
a transformer with a rated power of 315 kVA and a voltage ratio of 13.2kV/0.4kV filled with biodegradable oil,
through three-dimensional thermo-fluid dynamics simulations using the multiphysics scientific code Code Saturne.
This work is carried out as part of the EU Horizon 2020 BIOTRAFO project.