Effect of Voltage and Insulation Layer Thickness on the Temperature Rise Process of Polyester Film-Wrapped Coil in Instrument Transformers

The overheating phenomenon of instrument transformers may threaten their safe and stable operation in power grid. Through finite element (FEM) simulation, the temperature rising process of instrument transformers can be predicted, providing scientific basis for optimizing design and improving work reliability. A two-dimensional axisymmetric polyester film wrapped coil geometric model was established, and the electromagnetic and solid heat transfer equations were used in the Electrothermal coupling computation. The effect of voltage variation (500V-2000V) of coil on instrument transformer heating was investigated. Under normal conditions, the Temperature of the coil increased approximately linearly in the first 2 days and reached their highest values, then became stable. The maximum temperature of a coil with a voltage of 2000V was 108.5K higher than that of a coil with a voltage of 500V. The Electrothermal coupling model could well predicate the temperature raising process of coils in instrument transformers under different voltages. The higher voltage significantly increases the highest temperature of the coil under different operation conditions. The highest temperature of the instrument transformer was at the terminal of the coil.