Improvement of the electric field distribution in the medium voltage gas insulated inductive voltage transformers

Var, Melih
IVoltage transformers are commonly used in medium voltage systems for both protection and measurement purposes. These transformers are designed to satisfy the mandatory IEC requirements at the lowest possible cost. The average life expectancy of such transformer is about 20 years, reliability and robustness are of the utmost importance. The main cause of failure during rated operation is the deterioration of the solid insulation by partial discharges. Partial discharges, unless there is a manufacturing error, develops in the highest electric field zones in the transformer which means the expected life and reliability are limited by that zone. The purpose of this thesis is to improve the winding design of a problematic transformer such that the electric field distribution within the transformer will be as homogeneous as possible. The finite elements models of the winding layers and epoxy resin envelopment will be constructed and the fields will be inspected by 2D and 3D simulations. By utilizing the data gained from the simulations and considering the real life limitations prototypes will be constructed and tested with respect to according standards. The designs will be iteratively corrected to find the spot where the electric field is safely within the withstood limits of the respective insulating materials Moreover the feedbacks from the manufacturing process and the real life tests will be used to evaluate the tradeoffs between the different vi designs. The final coil design will be smaller in size due to the more uniform distribution of the electric field thus lowering the production cost. The reliability will increase and the routine test success rates will be improved. Additionally, it will be compatible with the IEC 61869-3 standard. 
Citation Formats
M. Var, “Improvement of the electric field distribution in the medium voltage gas insulated inductive voltage transformers,” M.S. - Master of Science, Middle East Technical University, 2017.