Abstract
The observation of the air gap discharge process is the basis of revealing the physical mechanism of gas discharge and establishing the accurate numerical simulation model. In order to obtain the variation characteristics at different development stages during the air gap discharge processes under positive and negative lightning impulses in this paper, repetitive discharge tests of 1 m rod-plate air gap under standard lightning impulse were carried out in the National Engineering Laboratory (Kunming) for Ultrahigh-voltage Engineering Technology. An improved discharge observation method, using electron-multiplying intensified charge-coupled device (EMICCD) camera, was adopted in the test. A series of discharge spatial-temporal distribution images with nanosecond exposure time and interval time were captured by changing the shooting time delay of the EMICCD in repetitive discharges. The complete discharge development process was reproduced by the image stitching. The development process and the characteristics of the air gap discharge under lightning impulse were analyzed qualitatively. The characteristics of the measured discharge current under the positive lightning impulse were discussed. The testing results and the analysis show that the shape and the development process of the ionization region of the streamer are quite different under different lightning impulses. There are spherical and fan-shaped streamer regions under the positive and negative lightning impulse, respectively. After the streamer runs through the entire gap, the leader develops from the rod electrode to the plate electrode (under the positive impulse) or from both the rod and the plate electrode to the middle area (under the negative impulse). Then the final jump occurs and the gap is broken down. If the streamer still cannot penetrate the entire gap when the applied impulse voltage exceeds the peak, the gap will not be broken down finally.
Highlights
Research on the discharge mechanism, the experimental observation and the numerical simulation of long air gap is the basis of external insulation design in the power system [1]–[7]
The second part focuses on initial corona and streamer discharges with weak light intensity, and the third part focuses on leader and final jump discharges with intense light intensity
The shooting time (T), time delay (Td), maximum light intensity (I) of the discharge channel, and morphological parameters of the ionization area are indicated in each image
Summary
Research on the discharge mechanism, the experimental observation and the numerical simulation of long air gap is the basis of external insulation design in the power system [1]–[7]. Observation of discharge development process is the foundation of discharge mechanism and numerical simulation. The Les Renardieres research group had carried out a systematic and comprehensive experimental study on 1.5-10 m air gap discharges under the positive and negative switching impulse [8]–[11]. They established a relatively complete set of observation and measurement methods. Personal use is permitted, but republication/redistribution requires IEEE permission
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