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An arc extinguishing lightning protection device with a multi-arc extinguishing chamber structure has been gradually applied to the overhead line lightning protection, but the process and key factors of the arc building of the internal multi-phase flow suppression arc still need to be studied. In this paper, based on the theory of arc magnetohydrodynamics and Euler’s high velocity flow field model, a simplified model of arc coupled polyphase longitudinal air flow in a multi-pipe structure is established, the approximate solution of the model is made, and the development process of polyphase air flow and the extinction mechanism of the arc are obtained. At the same time, the arc quenching process of polyphase longitudinal air flow is also studied experimentally. The experimental results show that the continuous arc of power frequency can be stopped quickly and will not be reignited under the condition of polyphase air flow.

The process of arc suppression with a super-strong arc-extinguishing gas (AEG) includes arc truncation and reburning suppression. In this paper, the plasma mechanics, the mechanics of the super-strong AEG, and the arc-reburning suppression by the AEG are all modeled. Combined with test data, the characteristics of arc truncation, pressure characteristics, and time characteristics of the AEG are analyzed, and the law of medium recovery and reignition suppression of arc fracture under the action of the super-strong AEG are discussed. The test results show that with a super-strong AEG, the arc-extinguishing threshold and time are 40 kA and less than 0.5 ms, respectively.

A dual-jet arc-extinguishing method is proposed in order to improve the performance of jet-extinguishing gaps for extinguishing large currents and reducing the lightning trip-out rate of power lines. Meanwhile, we studied the arc-extinguishing effect of the dual-jet non-equilibrium field gas flow. Based on this, a Double Jet Arc Extinguishing Gap (DJAEG) is developed. First of all, the jet field arc extinction modeling analysis is carried out by coupling the typical MAYR arc model with the jet field. Then, the COMSOL MUTIPHSICS simulation software is used to simulate the arc extinction of the DJAEG in the balanced flow field and the non-balanced flow field. Finally, the DJAEG extinguishment arc test is carried out through the construction of the power frequency continuous flow interruption test. The simulation results show that the velocity of the high-speed jet emitted by the DJAEG can reach 3000 m/s, and the arc can be extinguished within 4 ms. These results also verified that the dual jet non-equilibrium flow field has the characteristics of long jet sustaining time. The test results show that the DJAEG successfully extinguished the arc within 4 ms, and there was no reignition. This means that the dual-jet non-equilibrium field has an obvious arc extinction effect.

Due to the multi-phase tectonic movements in Chengbei Fault Zone, a superimposed pattern of Paleozoic buried hill and Cenozoic fault-step slope was developed on the North China platform. The fault–unconformity composite transport played a vital role in the oil and gas supply for the underlying buried hill and the distal high slope, resulting in the accumulation forming of multi-layer multi-type oil and gas. On the basis of seismic and well logging data, the characteristics of fault–unconformity composite transport in Chenghai buried hill and southern high slope were determined. And the reservoir-controlling mechanisms of fault–unconformity composite transport were revealed through oil and gas filling simulation experiments under different transport conditions. The results showed that the composite transport of fault and unconformity in buried hill zone was beneficial to the forming of large-scale reservoirs, and the dominant thick reservoirs or even negative tectonics under unconformity with abundant oil source were the main hydrocarbon accumulation area. As to the forming of reservoirs in the high slope, the key was the lithology configurations around the unconformity of “upper sand and lower mud” and “upper gravel and lower mudstone”. With the help of fault, the composite transport enables long-distance migration of oil and gas from the northern source rocks in Shahejie Formation, leading to hydrocarbon accumulation above the unconformity of Guantao Formation and even in the structural trough of southern high slope. These results revealed that fault–unconformity composite transport was helpful to hydrocarbon accumulation on a large scale, and even negative tectonics in buried hill below unconformity or structural troughs in high slope above unconformity are potential to form reservoirs. This provides a useful reference for theoretical research on reservoir forming in fault basins and a beneficial guidance for oil exploration in similar areas to a certain extent.

Hydrocarbon accumulates in multiple layers of the high, middle and low parts of Chengbei fault zone, in vicinity of Qikou Sag and Qinan Subsag, which represents a breakthrough for large-scale hydrocarbon exploration in recent years. Based on the size, abundance, and attitute of hydrocarbon inclusions, as well as their microscopic polarization and fluorescence characteristics, the hydrocarbon occurrence and the charging difference in the high, middle and low faulted terraces were analyzed systematically in this paper. There are two types of occurrence in the intergranular pores and fractures in the reservoirs, namely, the medium to light oil that shows green fluorescent light, and the solid bitumen charged with a certain amount of hydrocarbon that does not show any fluorescent light. This indicates that the zone has experienced at least two stages of hydrocarbon migration and accumulation, and that diversified forms of hydrocarbon exist in the reservoirs of the zone. The characteristics of hydrocarbon inclusions show that two stages of inclusions were found in the tectonic positions of different faulted terrace. The first-stage inclusions were developed in the early secondary enlargement of quartz grains, with a low degree of development abundance; while the second-stage inclusions were developed after the secondary enlargement of quartz grains, with a high degree of development abundance. The second-stage hydrocarbon inclusions of the reservoir samples obtained at tectonic positions of the high, middle and low fault terrace represent the main filling stage of the present-day reservoirs. Their fluorescence characteristics demonstrate the oil charging difference, which is the maturity of the hydrocarbon decreases as the terraces lift up along the slope. Identifying the hydrocarbon occurrence and charging differences from the perspective of inclusions is conducive to recognizing the regularity of hydrocarbon charging and migration and the distribution patterns in fault terrace zones, and lay the foundation for hydrocarbon exploration of slopes in the future.

To study the process by which an explosive high-speed airflow extinguishes an arc and the characteristics of arc dielectric recovery in a semienclosed space, this study investigates the principles and processes of the formation, development, and extinction of an arc under the action of a high-speed airflow. When the impact arc occurs in a semienclosed arc-extinguishing chamber, the high-speed air suppresses arc development. Due to the high-speed airflow, the arc cools at an accelerated rate; the arc energy weakens, breakpoints occur, and the continuity of the arc energy channel is broken, preventing the arc from forming in the arc-extinguishing chamber and extinguishing it. This article employs AUTODYN software to establish a model for high-speed airflow arc extinguishing in a semienclosed space and then reveals a process by which a high-speed airflow extinguishes an arc in such a space. To verify whether a high-speed airflow can extinguish an arc, we conduct experiments in which high-speed airflow extinguishes a large impact arc and a power frequency arc. We recorded the arc extinguishing process with high-speed and ordinary cameras. The time taken to extinguish the arc is approximately 7 ms, and the arc does not regenerate.

To reduce the damage from the power frequency follow current of distribution lines, a multi-fracture compression airflow arc-extinguishing structure is studied. The structure is mainly composed of a compression tube, a metal electrode, and metal connection fittings, and the multi-fracture compression airflow arc-extinguishing body is formed by the combination of packaging and insulation fittings. The body and the air gap are parallel to both ends of the insulator. When lightning strikes, the internal short gap of the main body and the air gap break down, and the lightning arc enters the arc-extinguishing body through the breakdown channel. In the structure, the arc is compressed by force to form internal and external gradients of temperature and to produce jet airflow. The jet airflow acts on the subsequent power frequency follow current arc, which is suppressed and extinguished. In this paper, a model coupling an arc and a compressed jet airflow in a multi-fracture compression airflow arc-extinguishing structure is established theoretically and simulated by simulation software. Finally, a power frequency follow current interruption test is carried out. The simulation results show that a high-speed airflow of 600 m/s is formed around the fracture at approximately 0.99 ms, and the airflow is proportional to the rate of temperature variation. The test results show that the power frequency follow current of 1.289 kA is cut off within approximately 3 ms without a reburning phenomenon. The effect of power frequency follow current interruption is obvious in the structure.

To avoid the restriction of the arc energy on the energy quenching of an arc and rapidly quench the arc to restore the insulation characteristics of the gas, the process of arc quenching by an explosion air shock wave is studied in this paper. The interaction between an explosion air shock wave and an arc is considered inside a cylinder structure so that concentrated pressure and airflow velocity can be produced. First, a coupling model of the explosion air shock wave and arc is developed theoretically. Second, according to the model, the explosion air shock wave and arc are simulated by finite element simulation software. It is found that the interaction between the explosion air shock wave and arc is most intense at 0.04 ms, the arc is driven out of the cylinder at 0.087 ms, and then, the arc is gradually quenched. Finally, the test results show that the arc is completely quenched at approximately 0.80 ms, and the value of the peak current is 1 kA. Although there is error between the simulation and test results, the effectiveness of the explosion air shock wave in quenching the arc is still verified, and the arc is quenched over a time scale of milliseconds.

In order to reduce the lightning trip-out rate of grid power lines, a kind of impulse quenching based multichamber arc quenching structure (IQBMAS) is developed by the authors. This kind of MAS can attract the lightning impulse arc into its arc quenching channel and truncate the impulse arc into multiple parts rapidly. In this case, the impulse arc will not develop into steady power frequency current, so the lightning trip-out can be avoided. In this paper, simulations and experiments are conducted to verify the arc-quenching effect of IQBMAS on the basis of expounding the operating principle of IQBMAS, establishing the arc model in the channel as well as deriving the relevant numerical equations. The test result shows that IQBMAS can extinguish the power frequency arc of 10 kV lines within 1.5 ms with no reignition.