Influences of surface tips of a shield ball on the discharge characteristics of a long sphere‐plane air gap under positive switching impulses

Influence of protrusions on the positive switching impulse breakdown voltage of sphere‐plane air gaps in high‐altitude areas

“…It can be seen from Fig. 10 that increasing altitude can decrease the switching impulse discharge voltage U 50 of the sphere-plane air gap: U 50 of the smooth shield ball at an altitude of 4300 m is 1883 kV, decreased by about 28.68% compared with that at an altitude of 50 m. The value of U 50 with burrs with lengths of 1-5 mm also decreased by 25.6-29.8% at the high altitude [23].…”

“…To compare with previous test data obtained in low-altitude areas [21,23], the lengths of burrs were separately set as 1, 2 and 5 mm. In practice, burrs appear on the surface of the shield ball at random positions, so it is necessary to study the influence of burr position on the discharge characteristics of air gaps.…”

“…The measurement methods are specified in [23]. The test procedure is still carried out in accordance with GB/T 16927.…”

“…It was pointed out in previous research [19][20][21] that it is inevitable that there are defects such as burrs and pits on the surface of the shield balls in the valve hall, which affect air gap discharge characteristics. Existing research [22][23][24] also simulated the electrical field intensity in the presence of tiny defects on shield balls and conducted switching impulse discharge tests thereon. The results show that the surface defects of the electrode will reduce the air gap breakdown voltage, and the test results have certain guiding significance.…”

Relaxation characteristics of ion jet formed across the short air gap in the cone–sphere electrode under positive polarity DC voltage

“…The repetition frequency and the amplitude of the corona current pulses changed with the gap voltage [15][16][17]. There was a corresponding relationship between the corona noise amplitude and the intensity of discharge development [18][19][20][21]. Therefore, the optical, corona current and corona noise were measured in this work to analyse the discharge process.…”