Post-arc current measurement and interruption performance of vacuum interrupter in DC interruption

In the DC grid, fault current rises very fast due to low impedance. Fast DC circuit breakers are needed to isolate faults and avoid a collapse of the common DC grid voltage. Based on the forced current zero (CZ) technology, the vacuum interrupter (VI) equipped with fast electromagnetic repulsion mechanism is a very promising solution of fast DC interruption. The experimental research on the DC interruption characteristics of a VI, namely by examining the post‑arc current (PAC) is presented in this paper. The dependence of the interruption capability on the PAC is analysed. What’s more, the failure modes of the VI under various experiment conditions are summarized. A former finding was that not all the arcing history which starts from the electrodes separating to the CZ has influence on the PAC but only a very short duration of several microseconds right before the CZ takes effects. New experiment results are added in this paper to support the former finding. Another former finding was that a longer electrode separation will bring about higher PAC. In this paper, both the influence of the arcing memory time and the electrodes separation are owed to a higher residual plasma density, which is verified by a model for calculating the residual plasma density and the continuous transient model (CTM) for calculating PAC.

Research on the detection of arc fault in series connection of landscape power supply

Aiming at the series fault arc phenomenon in landscape lighting and the hidden dangers of electrical fires, in this paper, a landscape power supply series fault arc model is constructed and its model is simulated. The simulation results show that when a fault occurs, the arc current becomes smaller (almost zero) due to the increase in the impedance of the lighting circuit; this phenomenon is called the “current zero off” phenomenon of the fault arc current. The current zero off phenomenon of the fault arc current is the main fault feature in the landscape lighting circuit. In this paper, the wavelet algorithm is used to detect the fault current waveform. According to the fault characteristics, by judging whether the modulus maximum value of the wavelet coefficient has periodic characteristics with an interval of 100±15 sampling points, it is analyzed whether a series-type arc fault occurs. The built physical model verifies the feasibility and correctness of the arc detection algorithm. The research results of this paper have certain reference value for the detection and application of fault arc.