Background. Various types of sensors, including inductive ones, are used for partial discharge diagnostics in the insulation of high-voltage equipment. Conventional approaches do not allow a comprehensive analysis of transient processes occurring in an electrical circuit with an inductive partial discharge sensor, as they fail to account for the sensor actual characteristics. Therefore, to obtain any reliable results, calibration of the measurement channel is required, which is not always feasible under real operating conditions. At the same time, accurate modeling of an inductive sensor that considers all physical phenomena occurring during the passage of a partial discharge impulse current, enables not only to determine its characteristics but also to calculate the apparent charge, which is the key parameter to assess insulation condition. Thus, it is relevant to develop a model that eliminates the need for calibration of the measuring channel and directly links the measured signal with the physical parameters of the discharge.
Materials and methods. A hybrid simulation model has been developed based on combination of the numerical solution of Maxwell’s equations using the finite element method with the analysis of an equivalent electrical circuit. The model accounts for the magnetic field, displacement currents through inter-turn capacitances, and interaction with the external circuit. Discrete Fourier transform and harmonic superposition method are employed for impulse signal analysis. The apparent charge is calculated by integrating the current over a quarter of the period.
Results. The author has developed the hybrid simulation model that allows us to calculate the sensor inductance with an error of 3,1 % compared to the analytical solution, determine the resonant frequency and quality factor (Q-factor), reconstruct the partial discharge impulse waveform using the first and third harmonics with an error of 1,84 %, and calculate the apparent charge value.
Conclusions. The proposed model allows for the design and analysis of inductive partial discharge sensors without requiring measurement channel calibration, directly correlating the registered signal with the physical parameters of the discharge. The model is universal and can be applied both for conventional measuring transducers and systems based on sensors without a ferromagnetic core. The results have been validated through comparison with analytical calculations and can be used for automated insulation diagnostics.