7th Asia-Pacific Conference on Plasma Physics, 12-17 Nov, 2023 at Port Messe Nagoya

Vacuum arc erosion behavior in hybrid DC interruption
Yifei Wu, YiWu
School of Electrical Engineering, Xi'an Jiaotong University
e-mail: yifei208@xjtu.edu.cn

Vacuum arc erosion has an important impact on theperformance of hybrid DC circuit breaker. An inherent
property of the vacuum arc is the generation ofmicroparticles. This paper focused on the dynamics ofmicroparticle and erosion behavior in high-current
vacuum arc. The arc was sustained with AC 110 Hz
between two butt CuCr alloy contacts with a diameter of
10 mm. An in situ microparticle diagnostic system
suitable for vacuum arcs was developed.
Aiming at the problem of low signal-to-noise ratio of
microparticle images in high-current vacuum arcs, a highresolution analysis of microparticle images based on
Gaussian pyramid interpolation technology and nonsharpening masking method was proposed. On this basis,using the characteristic that the eigenvalues of the Hesse
matrix only respond to the spot-like structure, a spotenhanced filtering function suitable for 2D images isproposed, which can be used to obtain the boundary of
microparticles accurately. Finally, the Otsu algorithm wasused to complete the reconstruction of the microparticle
images. Besides, aiming at the problems existing in
microparticle volume statistical algorithm, a metal
particle matching strategy based on direction-oriented
cross-correlation algorithm was proposed, which reduces
the false matching between microparticles.
Based on the diagnostic system, three sources of
microparticles were observed and the corresponding
motion characteristics were obtained by our method. The
influence of current, Cr content, electrode gap andopening speed was investigated in this paper. The results
indicate that when the peak current is not greater than 5kA, the ability of CuCr alloy cathodes to produce
microparticles decreases with the increase of Cr content.
When the peak current is not less than 6 kA, the CuCr30
cathode has the strongest ability to suppress microparticle

Figure 1. Schematic diagram of the experimental setup
used for electrode erosion behavior in vacuum arcs.

production among the three tested materials.
High-voltage trigger equipment and specially designed
cathode structure were used to investigate the influence ofelectrode gap on vacuum arc erosion characteristics
quantitatively. The experimental results show that whenthe electrode gap is 3mm, the cathode microparticle
ablation is the most serious due to its highest cathodesurface temperature. By contrast, the influence ofelectrode gap on the cathode erosion characteristics wasobtained by using a specially designed anode structure
which was used to avoid the interaction between anodespot and cathode surface. The results indicate that theobserved cathode microparticles in this study are almost
entirely attributable to the interaction between the anodespot and cathode surface.
Besides, the influence of opening speed was investigatedwithin the range of 0.65m/s to 3.42m/s. The results showthat when the opening speed is 1.15m/s, the ablation of thecathode is the most serious. When the opening speed is notless than 1.88m/s, the opening speed has little effect in theablation of the cathode. In addition, the erosion
characteristics under the action of external transverse
magnetic field were also studied, revealing the effects ofmagnetic field strength on the erosion amount, as well as
the speed and diameter of the ablated microparticles.
The results presented add to the understanding of
microparticle behavior in high-current vacuum arcs. They
will assist in improving the design of vacuum arc
electrodes, particularly by allowing appropriate material
selection for specific short-circuit currents andappropriate opening speed for specific breaking condition,with the ultimate goal of minimizing the production ofmicroparticles.

Figure 2. (a) An image of microparticles in a vacuum arc.
(b) Sharpened image of (a) obtained by unsharp masking
algorithm. (c) Blob enhanced image of (b) obtained byimproved blob enhancement filter. (d) Binarized image ofimage (a).