Calibration method of radio interference measurement result in high-voltage side of corona cage

Corona cage is one of the key measures for researching the radio interference (RI) of transmission lines. However, calibration is needed when the measurement result at the high-voltage side is used to calculate the excitation function. Hence we have studied the calibration methods. Firstly, a formula of the calibration factor is developed based on the excitation function theory and the transmission line theory, and some simplifications of the formula are made for different situations. Then, we propose two calibration methods, and one determines the parameters in the calibration factor formula through numerical calculation and then calculates the calibration factor, the other determines the calibration factor based on the measured calibration curves. Taking the 6×LGJ-720/50 conductor as example, its calculated calibration factor is 1.7 dB and the result gained by the calibration curve is 2.2 dB. The two results are close to each other. In addition, the impact of the conductor parameters on the calibration factor is analyzed, and the result indicates that this impact can be ignored in the HVDC corona cage in China.