Time-domain Characteristics Of Corona Current Pulses Under High Voltage Hybrid AC-DC Conductors

Running HVAC and HVDC transmission lines in same corridor is an effective way for improving the transmission capability of existing corridor and saving land resources.However,the new electromagnetic enviromental problems also come along,and one important aspect of them is the radio interference caused by corona discharge from high voltage transmission lines.This paper focuses on the source of radio interference from transmissino line,namely the corona current pulse,investigating the time domain characteristcs of corona current pulses under the influence of ajacent AC-DC conductors.Meanwhile,the measuring method of corona current pulse,the characteristics of quansi peak response from radio interence receiver,the relationship between corona current pulse and ion current waveforms are also systematically studied.The work of this dissertation can provide references for the prediction and analysis of radio interference from hybrid AC-DC high voltage transmission lines.Firstly,a comparative study about two low potentail side measuring methods for corona current pulse is carried out.Based on indoor small corona cage,the corona current pulses are obtained respectively from conductor side and cage side,and the waveforms of the corona current pulses are systematically compared including the influence of sampling resistors.The circuit model and transmission line model are proposed repstively for two different measuring mehtods,and the simulation results are in good agreement with measurement results which verifies the validity of proposed models.At last,the relationship between both methods are theoretically analysied based on the proposed models.Secondly,the detailed time domain characteristics of AC and DC corona current pulse from high voltage hybrid AC-DC conductors are systematically investigated based on corona cage platfrom.The distribution pattern,waveform parameters,repetition frequency,starting characteristics,time interval between secondary pulses,distribution of pulse amplitude and so on about the corona current pulse are analized,obtaining the influence of ajacent AC and DC conductors on the characteristics of corona current pulse.Meanwhile,by applying a simplified ion cloud model,the modulation effect produced by ajacent AC conductor on negative corona current pulse time intervals are derived and analized.At last,given the obvious change of distribution pattern and repetition of corona current pulse caused by the hybrid conductors,an EMI receiver model in quasi-peak detection mode is established and the influence of pulse amplitude,distribution pattern and repetition frequency on the quasi-peak response of EMI receiver are investigated.At the same time,to find out the relationship between corona current pulse and ion current waveform,the experiment about synchronous measuremt of corona current pulse and ion current wavefrom is carried out.The relationship between them is thus revealed,and one method to calculate the ground level ion current waveform based on corona current pulse is proposed.