Finite Element Simulation of Moisture Transport in Cellulose Insulation Material of Power Transformers

Sammanfattning: Power Transformers are an important and complex part of the electrical transmission technology. One of the main producers of these transformers worldwide is Hitachi Energy, for which this work has been done.This work proposes to create a simulation model for the transport of moisture in transformer insulation material using Finite Element Method implemented in COMSOL 6.1. The transport of moisture in cellulose material is a complex process but the model assumes that diffusion is the dominant transport mechanism. For that, a model based on Fick’s second law is used. The value of the coefficient is defined experimentally at different temperatures. But some of the tools used for their measurements are inaccurate, for example at higher temperatures or because they only give an average moisture content at a given time. Then a difficulty is to assert the simulation’s validity by comparison with the experimental data. In the present work, care is given to validate the model by comparison with precedent works.Using experimental data coming from internal sources at the company (Hitachi Energy), curves are then drawn to see the process of ingress and egress of moisture in pressboard material under different boundary conditions to simulate several steps of the production process. Possible future research directions include the use of data from future experiments and the creation of a more complex model to simulate a more realistic geometry.