Analysing the influence of geometry and pressure on corona discharges

Abstract

In this work, the authors propose an experiment aimed for undergraduate laboratories with the aim of introducing different novelties as a topic for practical sessions or student projects. The topics here investigated are appropriate for students with intermediate physics knowledge. Corona discharges are little studied in regular physics courses despite their practical importance in different areas, such as the distribution and transmission of electrical power, generation of ozone, particulate removal in air conditioning systems, improvement of wettability in polymeric materials, or the removal of electrostatic charges from the surface of airplanes among others. This work analyses the minimum voltage level leading to corona discharges and the influence of geometry and atmospheric pressure because these two factors are the most influential to determine the minimum voltage at which corona discharges appear.

Studying the breakdown electric field in uniform and non-uniform air gaps

“…Note that if the applied voltage ΔV is sufficiently high, a complete electrical breakdown will occur, i.e. an electrical spark or arc will be formed that spans the entire gap without prior corona activity, since corona is typical of non-uniform field gaps [14]. Although most practical gaps exhibit some degree of non-uniformity, uniform gaps have been widely used in the high voltage field because results with these gaps are easy to replicate.…”

“…Figure 7 shows the geometry of the non-uniform sphere-plane gap and the mesh used in the FEA simulations to determine the electric field strength at the lowest point of the sphere during corona breakdown conditions. Table 2 summarizes the experimental values of the corona extinction voltage for different spheres presented in [19], as well as the electric field at the lowest point of the spheres obtained by means of FEA simulations.…”

Application of Image Sensors to Detect and Locate Electrical Discharges: A Review

“…It is well-known that air molecules in the vicinity of a high-voltage electrode become ionized when the electric field exceeds the inception threshold value [ 69 ]. During the ionization process typical of an electrical discharge, the electrons released change their energy levels, thus emitting ultraviolet and visible photons, broadband electromagnetic waves, and acoustic emissions, as well as generating chemical components such as traces of nitric acid or ozone, among others [ 70 ]. In [ 13 , 71 , 72 , 73 ] the UV and visible spectra of electrical discharges have been presented, showing that they cover the 200–700 nm range.…”

Use of DSLR and Sonic Cameras to Detect and Locate High-Voltage Corona Discharges

“…When the electric field in the vicinity of an energized electrode that is surrounded by air exceeds an inception value, the air molecules become ionized [ 47 ], causing electrical discharges. Throughout the ionization process, the excited and released electrons change their energy levels, so that ultraviolet and visible photons are emitted, as well as broadband electromagnetic emissions, in addition to generating different chemicals including ozone (O 3 ) or traces of nitric acid [ 48 ]. The ionization process also generates broadband audible noise (AN) in the range from one to several kilohertz [ 49 ] due to the rapid moving electrons colliding with neutral air molecules, with a sudden transfer of kinetic energy, which is equivalent to small explosions that are occurring at the corona sites, thus generating AN [ 50 ].…”