The Study Of Corona Onset Criterion Of HVDC Transmission Lines

With the rapid development of Ultra-High Voltage Direct Current (UHVDC), a series of electromagnetic environment problems are generated due to the corona discharge. In this paper an optimized charge simulation method based on the combination of optimization method and charge simulation method (CSM) is used, which is testified to be valid. The electric field distribution of the conductor surface and space is calculated, then the roughness coefficient of the Aluminium Conductors Steel Reinforced(ACSR) can be obtained. Based on the corona dicharge model, the positive and negative corona discharge mechanism is explained in detail. From different breakdown criteria, the general expressions of the corona discharge inception criteria are obtained. The electrons number Q of the electron avalanche head which is a quantitative measure of the corona onset criteria is discussed, which is proved to be valid by the classical formula. Based on the practice model of actual power transmission lines, the effect of avalanche space charge to the corona onset voltage and corona onset field is analyzed. Finally, corona onset condtions is analyzed under different operating modes of HVDC transmission lines, such as unipolar, bipolar and double-circuit transmission lines. The research results can provide some references to HVDC transmission line design.