Abstract
Corona discharge characteristics are measured in a corona cage. The difference is found between the q–u curves under double exponential and damped oscillation surges. The behavior of the minor loops is revealed for the q–u curves under positive and negative damped oscillation surges. An extended improvement is made on the traditional approach for modeling of the q–u curves under damped oscillation surges. The extended approach has the capability of describing the complicated trajectory feature of the minor loops. On the basis of the extended approach, an efficient method is proposed for performing lightning surge analysis of overhead lines considering the corona effect. In the proposed method, an overhead line with corona is divided into a certain number of line segments. Each segment is converted into a circuit unit consisting of a non-linear branch and a linear circuit. With these circuit units connected in sequence, a complete equivalent circuit is constructed for the overhead line with corona. The transient responses can be obtained from the solution to the equivalent circuit. Then, the calculated results are compared with the field test results on a test overhead line.
Highlights
Analysis of the propagation behavior of lightning surges on overhead lines is essential for lightning overvoltage protection and insulation coordination of electric power apparatus
The q–u curves under double exponential surges descend monotonically, whereas those under damped oscillation surges behave as the minor loops
In order to characterize the complicated trajectory feature of the minor loops, an extended approach has been presented by considerably improving the traditional approach
Summary
Analysis of the propagation behavior of lightning surges on overhead lines is essential for lightning overvoltage protection and insulation coordination of electric power apparatus. In the calculation of lightning overvoltages, surge corona is taken into account by its charge-voltage characteristic, namely the q–u curve. The distortion and attenuation were always calculated according to the q–u curves under double exponential surges, no matter what the actual surge waveshapes are [3,11,12,13]. Some work suited to this need was reported in literature [16,17,18,19]; the systematic research results were still not reported in the previous work In view of this situation, an attempt is made in this paper to comprehensively investigate the corona effect on the distortion and attenuation of damped oscillation surges. The proposed method can effectively predict the distortion and attenuation of damped oscillation surges on overhead lines with corona. We further discuss the calculated results in the presence and absence of the minor loops to inquire into the influence of the minor loops on the distortion and attenuation of damped oscillation surges under positive and negative polarities
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