Studying the Frequency Characteristics of Inductive Sensors Used in Partial Discharge Measurement Circuits
Anton ZHUYKOV, Polina KOLPAKOVA, Daniil MATVEEV, Mihail FROLOV, Sergey HRENOV · Elektrichestvo · 2023
The results obtained from measuring the characteristics of partial discharges (PD) inside of electrical equipment insulation using the electrical method should be analyzed with taking into account the frequency responses of both the test facility and measurement circuit components, especially the sensors that produce the response to PD signals. The article sets out methodical principles of the approach to determining these frequency responses, which minimizes the measurement errors. The frequency responses of inductive sensors of two kinds – based on the principles of current and voltage transformer – are given and analyzed, which opens the possibility to design sensors for particular measurement objectives. For sensors based on the current transformer principle it is shown that the decreasing pattern of the phase-frequency response limits their operation frequency range. For sensors based on the voltage transformer principle the influence of the type of ferrite core and the measuring device input impedance on the frequency responses is analyzed. It is shown that by selecting the core material it is possible to control the response duration and provide separate recording of frequently repeating discharges. The condition for ensuring an oscillatory pattern of the response from an inductive sensor connected to the measuring device low-impedance input is determined. Recommendations on the sensors design to reduce distortion and attenuation of signals are given.