Experimental Study on Impulse Corona Characteristics of HVDC Conductors With Space Charges

Impulse corona characteristics are very important for the analysis of overvoltage along overhead transmission lines. For DC line, the space charge due to normal corona may affect the impulse corona characteristics. The paper develops a circuit for combined application of DC and impulse voltage to measure the effect of space charges on impulse corona characteristics along DC conductor. Based on the circuit, a test platform with a corona cage was established. By measuring the q-u curve, the impulse corona onset voltages under different DC pre-voltages were obtained. It was proposed that the space charges would affect the corona onset voltage. The space charges of the opposite polarity would weaken the corona and reduce the impulse corona loss, which is beneficial to the overvoltage wave propagation. While the space charges of the same polarity would enhance the corona and increase the impulse corona loss, which is not conducive to the overvoltage wave propagation. In addition, the influence of wave front time and conductor radius on the impulse corona characteristics was measured. The test results are important references for the transient overvoltage protection of overhead HVDC lines.