Plasma fluorination on epoxy resin surface and its effect on flashover properties

Abstract

Epoxy resin is the main material of spacer in a gas insulated transmission line and other gas-insulated equipment. During long-term operation, the charge accumulates on the surface of the epoxy resin, which will distort the electric field and thus accelerate the failure of the insulation. In this paper, the surface of the epoxy resin was fluorinated by dielectric barrier discharge at different times. The surface physical, chemical, and flashover properties of the samples before and after modification were measured. The results show that the method used in this paper can graft fluorine on the surface of the sample, change the surface roughness, and make the electron trap shallower and the hole trap deeper. The appropriate modification time can reduce the charge accumulation on the surface, hinder the formation of flashover channels, and improve the surface flashover voltage, showing potential for use in the improvement of the insulating performance of insulating materials.

Surface flashover in 50 years: Theoretical models and competing mechanisms

“…In this case, surface conductance fails to affect the surface charge accumulation and dissipation [142]. To accelerate charge dissipation through the surface, various surface modifications, such as fluorination [143][144][145][146][147], ozone treatment [148,149], plasma deposition [150][151][152][153], and coating of non-linear conductivity materials [138,139,141,154,155], were adopted by many researchers to enhance the surface conductivity.…”

“…In region II, surface flashover exhibits a negative dependence on the energy depth of traps but depends positively on the density of shallow surface traps and surface conductivity. The surface modification methods in region II includes fluorination [143][144][145][146]176], plasma deposition [150-153, 168, 177], non-linear conductive material coating [138,139,141,154,155], ozone treatment [148,149], (III) Region dominated by leakage current. When surface conductivity exceeds a critical value, the leakage current through the surface increases rapidly, which degrades the insulation properties of materials and decreases surface flashover voltage.…”

“…(a) Schematic of the energy band structures of polymeric materials [77]. (b) Relationships between V f and surface trap parameters, that is, (b‐i) deep surface trap level [70, 71, 114, 167], (b‐ii) deep surface trap density [71, 95, 114, 167], (b‐iii) shallow surface trap level [71, 145, 152, 160, 168], and (b‐iv) shallow surface trap density [71, 145]. (c) ‘U‐shaped’ dependence of V f on surface trap level.…”

Improved DC surface insulation performance of epoxy resin by gradient plasma fluorination

“…Considering the effects of pre-charging, the samples are charged with ±5 kV, ±7 kV and ±9 kV for 2 min, and then the voltage is boosted or the voltage is directly boosted without pre-charging, respectively. In order to reduce the experimental error, samples under each condition are tested for ten times at a voltage boost speed of 0.1 kV s −1 and the Weibull model [22] is used for analysis. The flashover voltages of samples with uniform treatment for different duration and with gradient treatment after direct voltage boost or charging for 2 min at different voltages are shown in figure 11, where (a) and (b) are charged with positive and negative polarity voltages respectively.…”

“…At present, there are many methods to regulate the surface conductivity distribution of disc insulators, including the coating method [17], direct fluorination method [18], magnetron sputtering method [19], plasma treatment method [20,21], etc. Among them, plasma fluorination is considered to be a promising surface treatment method due to its advantages of high efficiency and economy [22,23].…”