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Multi-chamber arc-extinguishing has been widely researched and used to protect transmission and distribution lines from lightning. Its principle is to divide a long-gap arc into multiple short-gap arcs using multiple semi-enclosed arc-extinguishing chambers. To study the dynamic evolution of arc plasma in an arc-extinguishing chamber, we establish a three-dimensional simulation model of arc plasma in a semi-enclosed arc-extinguishing chamber by solving the Navier–Stokes and Maxwell equations. We analyze the dynamic evolution of an arc from the inside of the chamber to the outside. An impact current test platform is built and the arc motion is photographed by a high-speed camera, revealing the acceleration of the arc in the semi-enclosed chamber. Finally, the influence of chamber dimensions on key arc parameters is analyzed. In the simulation, the time when the arc completely moves out of the chamber and is extinguished is consistent with the experimental images, which verifies the accuracy of the simulation model. The arc temperature, chamber pressure, and airflow velocity first increase in an oscillating manner and then slowly decrease with time. The change of the opening diameter will lead to the obvious change of the arc temperature maximum. The opening diameter is the main chamber dimension that affects the arc temperature. The electrode spacings have the most obvious effect on the maximum pressure in the chamber. The minimum pressure in different chamber dimensions is lower than the atmospheric pressure. The influence of opening diameter, distance from central axis to closed side, and opening wall length on the maximum airflow velocity is the same, and the maximum airflow velocity decreases with the increase in these dimensions. The influence of electrode spacing on the maximum airflow velocity is opposite to them. [ABSTRACT FROM AUTHOR]

Under DC voltage, charge accumulates on the break insulation of mechanical DC circuit breakers, distorting the local electric field, which increases the risk of break insulation failure. Glass-fiber vacuum-impregnated epoxy resin can be used as an insulation material for DC circuit breakers owing to its excellent mechanical and electrical properties. We have created a system to measure the surface potential of an epoxy resin in different gases. The accumulation and dissipation of the surface charge in air and SF6 are determined, and the effects of air and SF6 are compared. The results show that the polarity of the surface charge is the same as that of the applied DC voltage, and that the main source of the charge is from Schottky charge injection. In SF6, the charge density is higher than that in air, and its decay rate is slower. The decay law of the surface potential in SF6 can be characterized by two exponential superposition formulas. In the early stage, surface charge is attenuated mainly by being transferred along the surface of the insulator and neutralized by gas ions. In the late stage, surface charge is attenuated mainly by transferring through the volume of the insulator. [ABSTRACT FROM AUTHOR]

Amorphous alloy is increasingly widely used in the iron core of power transformer due to its excellent low loss performance. However, its potential harm to the power system is not fully studied during the electromagnetic transients of the transformer. This study develops a simulation model to analyze the effect of transformer iron core materials on ferroresonance. The model is based on the transformer π equivalent circuit. The flux linkage–current (ψ–i) Jiles–Atherton reactor is developed in an Electromagnetic Transients Program-Alternative Transients Program and is used to represent the magnetizing branches of the transformer model. Two ferroresonance cases are studied to compare the performance of grain-oriented Si-steel and amorphous alloy cores. The ferroresonance overvoltage and overcurrent are discussed under different system parameters. Results show that amorphous alloy transformer generates higher voltage and current than those of grain-oriented Si-steel transformer and significantly harms the power system safety. [ABSTRACT FROM AUTHOR]

We prepared nano-C60 based insulating oil, which has the potential to overcome the application barriers of nanomodified insulating oil. We find that nano-C60 based insulating oil has an excellent stability. Its electrical performance increases by 17.9%, 9.3%, and 8.3% for AC and positive/negative lightning impulse voltage, respectively. We believe that C60 molecules have a strong capacity to absorb electrons and can capture photons in a streamer, which may weaken photoionization in the streamer and thereby improve the electrical performance of insulating oil. [ABSTRACT FROM AUTHOR]