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

Electrical arc behavior, controlling and their applications in switchgearYiWu, Hao Sun
the State Key Laboratory of Electrical Insulation and Power Equipment, School of ElectricEngineering, Xi'an Jiaotong University
e-mal: wuyic51@xjtu.edu.cn
experimental installation is shown as Fig.2. The tested
degradation rate in our lab is above 99%. Compared withother methods, SF6 degradation with arc plasma canobtain a higher degradation rate.

Arc Voltage(V)Fig.1 The arc erosion to the Tungsten electrode in N2

Arc Current(A)Switchgear is the vital equipment widely used in theelectrical power system, to protect the whole systemfrom fault damage. Electrical arc plasma is a normal
phenomenon appeared during the switchgear interrupting
the current. Understanding and controlling of arc plasma
is very important to improve switchgear performance,
propose new scheme for current interruption andgreenhouse gas SF6 processing. This talk presents arc
behavior and controlling for switchgear, including arc
erosion measurement, arc oscillation controlling inDCCB and arc processing SF6 gas for environmental
protection. Research results are used and support greatly
the development of the equipment.
Firstly, the arc erosion behavior is described here
based on the measurement. Electric arc with hightemperature up to several tens thousand K, leads toserious erosion to surroundings, especially to electrode.
Measurement of arc erosion is a challenging work due tothe high temperature of the arc and quick action between
arc and electrode. The special high-speed visualization
technique is proposed. The arc erosion behavior isachieved by a high-speed camera coupled with thenarrow band-pass filter. ICCD is used to capture thethermal image of the electrode coupled with the beam
splitter equipment and optic filter. Based on this method,
the total mass and trajectories of droplets splashed fromthe electrode surface under different current, arc medium
and electrode materials are recorded and analyzed.
Secondly, arc control is helpful to propose new current
interruption principle. DC current interruption is much
more difficult compared with AC interruption, especiallyin medium or high voltage area. The exiting HV DCCB,
such as hybrid circuit breaker is very expensive, which is
not favorable to be extended in real system. This talkproposed one new method for DC interruption. Throughthe external magnetic field excited by AC source, it
makes the arc voltage oscillation and achieves thecurrent zero of mechanical switch. Fig.3 shows the arc
voltage oscillation influenced by a magnetic field. The
frequency and amplitude of oscillation is controlled bymagnetic field. Based on the arc oscillation, the DC
current flowing through the mechanical electrode candecrease to zero.
Finally, the degradation of SF6 gas for switchgear
based on arc plasma is presented here. SF6 gas is widely
applied as the insulation and current interruption medium
in the high voltage switchgear. However, SF6 gas used inexisting equipment will exit the application due to its
greenhouse gas effect. Arc plasma torch with hightemperature is adopted to decompose SF6 and form
nontoxic products. The setup of SF6 degradation

Time (ms)Fig.2 Arc voltage oscillation affected by magnetic field
Input1

CathodeWatercoolingsystem
AC[-]

[+]

[+]

[+]

[+]

input 2SF6H2ArN2PowerDCexit

Arc plasma torch
absorberFig.3 Setup of SF6 degradation experimental installation

References[1] Yufei Cui, Yi Wu, Chunping Niu, et al. Evolution ofanodic erosion components and heat transfer efficiency
for W and W80Ag20 in atmospheric-pressure arcs. [J]Journal of Physics D: Applied Physics 53(47), 2020.
[2]Hao Sun, Hu Long, Yi Wu, Simulation andexperimental study on the degradation of the greenhousegas SF6 by thermal plasma, Environmental Research,216,114411,2023.