Analysis of Induced Current and Voltage of GIL Enclosure Based on Equivalent Circuit Model and Finite Element Computation

Gas insulated transmission line (GIL) can have large induced current and induced voltage on the enclosure. Thus it is necessary to accurately calculate these values and study the influencing factors. Using Biot-Savart’s law, the self-impedance and mutual inductance of the metal part of the GIL system can be obtained. By establishing an equivalent circuit model and a finite element (FE) model corresponding to the 220 kV/4000A GIL, the magnitude of the induced current and voltage is calculated and compared. The error of the induced current calculation in both models is within 3%, and the error of induced voltage calculation is within 6%. The equivalent circuit model is used to analyze the induced voltage distribution along the axial enclosure under normal operating conditions, it is found that the value presents U-shaped distribution and it is much smaller than the safety critical value. Finally, it is analyzed that introducing three-phase interphase shunts to the enclosure will greatly reduce the current flowing into the earth and the potential to ground.