769 / 2022-03-31 21:47:44

Breakdown evolution characteristics under repetitive pulse voltage in BOPP films

Polyproplene film,Breakdown,Trap,Repetitive pulse

Purpose/Aim

When BOPP film capacitors work in electric power systems and pulse power systems, they are often subjected to multiple microsecond pulse voltage shocks, which cause the capacitors to exit operation prematurely. In order to improve the service life and working stability of capacitors, it is urgent to study the breakdown failure mechanism and discharge evolution process of BOPP films under repetitive microsecond pulse voltage (RMPV).

Experimental/Modeling methods

In this paper, the breakdown evolution characteristics of BOPP under RMPV in atmospheric environment are systematically studied. Firstly, we use the camera to record the time evolution images that shows each stage of BOPP discharge breakdown. Secondly, the mesoscopic morphology after BOPP breakdown was observed with super depth of field microscope. Subsequently, the potential distribution and evolution of BOPP surface under high pressure were monitored by non-contact probe, and the trap distribution was calculated by isothermal surface potential decay method. Finally, from the perspective of energy injection and charge transport, the breakdown failure evolution mechanism of BOPP under RMPV is revealed.

Results/discussion

In an atmospheric environment, the breakdown of the repetition rate microsecond pulse begins with a number of filament channels diverging from the center of the high voltage electrode, and then the discharge channel shrinks into a bright spark channel. As a result, the spark channel gradually dies out and shrinks to the direction that is close to the center of the high voltage electrode. Observation by ultra-depth of field microscope, the BOPP film was ablated and vaporized where the spark passage passed, and significant trees were also left in other positions. The surface potential distribution was in good agreement with the experimental phenomenon that the maximum potential appeared near the high-voltage electrode, and the potential decreased rapidly with the test point away from the center. In addition, the energy injection of excitation source and the trap parameters determine the BOPP discharge evolution process.

Conclusions

BOPP insulation failure under repetitive pulse is an electrical and thermal accumulation process. Due to the long-time of repetitive pulse, the damage process of BOPP discharge is not only related to the voltage amplitude of excitation source, but also depends on the effect of excitation source energy injection and trap distribution on the charge transport process.