Direct Current Interruption Research Articles

A comparison of two piezoelectric actuator concepts for fast mechanical switching in DC hybrid circuit breakers.

Amplified piezoelectric actuators have gained considerable attention due to their inherent advantages, including rapid response, reliability, and efficiency, making them promising candidates for Direct Current (DC) switching applications. They can operate in two distinct operational modes: Block-Free (B-F) and Free-Free (F-F) configurations. These two modes offer diverse mechanical constraints and are chosen based on the application's specific requirements. This study aims to present a comparative assessment between the two modes to evaluate each configuration's applicability in DC fast switching. Accordingly, the principle behind each actuation scheme was illustrated, and both designs were modeled and analyzed by the finite element method. Subsequently, two prototypes were assembled, each resembling a different operational mode. The established prototypes were then subjected to actuation and interruption tests to investigate their travel and switching performances. Comparative results revealed that while block-free could deliver a higher apparent stroke, the accumulated gap for each configuration is almost the same. Both actuators demonstrated high capability when utilized as actuation units for fast vacuum mechanical switches integrated into a hybrid circuit breaker for DC interruption. However, the free-free operation excelled in terms of fast response, as it managed to clear the mimicked fault current faster than the block-free configuration.

Experimental investigation on magnetically controlled air arc oscillation characteristics for DC interruption

With the development of the direct current (DC) power grid, the research of the forced current zero techniques in DC circuit breakers is of vital importance. Through applying an external alternating transverse magnetic field to an air arc confined by insulating walls, the arc can oscillate in a specific pattern, which is defined as ‘magnetically controlled arc oscillation’ in this article. The air arc oscillation characteristics are investigated through arc voltage spectrum analysis and arc motion captured by a high-speed camera. It can be found that the arc motion can be divided into a gliding process and a stretching process. The arc voltage oscillates at a particular frequency, which is nearly twice the magnetic field frequency. The basic arc oscillation pattern can be described from the aspects of arc voltage, arc column length and arc root velocity. Furthermore, this article proposes a DC breaking scheme based on the investigated magnetically controlled air arc oscillation characteristics. The forced current zero crossing point can be created in the resonant process between the oscillated air arc and the parallel-connected inductance-capacitance (LC) commutation path. Based on the proposed DC breaking scheme, interruption experiments are carried out, and it is observed that a current of 4.2 kA can be interrupted within several milliseconds. The feasibility of DC interruption based on magnetically controlled arc oscillation has been proved.

A mixture of Si3N4 powder and SiO2 sand as a novel DC arc quenching medium for improvement of the current-limiting performance of a model electric fuse

A current-limiting and consequent direct current (DC) arc interruption requires an increase in arc resistance rarc for a DC fuse. Flattery silica (SiO2) sand has been used as an arc quenching medium in fuses for decades. However, there are few reports about a novel arc quenching medium which enables more rarc increases compared to flattery SiO2 sand. This paper uniquely selected a novel arc quenching medium based on the following material properties: (1) electrical resistivity and thermal conductivity in the solid phase, (2) the possibility of rarc increasing in the gas phase, (3) the possibility of electrical insulation after re-solidification, and (4) the cost of materials. As a result, we originally selected a powder mixture of silicon-nitride (Si3N4) and flattery SiO2 sand as a promising novel arc quenching medium. Therefore, DC interruption experiments were performed using a Si3N4/flattery SiO2 sand powder mixture under different Si3N4 concentration conditions. As a result of 1000 A DC arc quenching experiments, the utilization of Si3N4 powder with the flattery SiO2 sand successfully increased the arc resistance rarc during the arc quenching process. The increasing Si3N4 concentration exhibited a further increase in rarc during the arc quenching process. As a result of the rarc increase, the arc quenching time was significantly shortened to 30 ms for 30 wt.% Si3N4 conditions from 54 ms for the SiO2 sand conditions. In addition, utilization of Si3N4 powder achieved high insulation resistance over few MΩ after DC arc interruption. The above results clearly indicate that utilization of Si3N4 powder with flattery SiO2 sand can increase the DC interruption performance of the fuse.

Contribution of the Liquid Phase on Direct Current Interruption by a Forced Fluid Flow

The rising amount of medium voltage direct-current systems requires novel solutions for DC switching. The interruption of direct-currents is accomplished by enforcing a current zero, which can only be achieved when the arc voltage of the switching device raises above the grid voltage. On way to achieve this, is to force the arc into narrow channels by an imposed fluid flow. The increasing arc voltage than not only depends on increased cooling due to phase change but also on the mechanical elongation of the arc enforced by the fluid stream. Hence, the interaction of the fluid flow and the arc should be studied in more detail. For this, the switching characteristic of selected dielectric liquids are examined. Using a self developed setup, direct-current interruptions at a constant voltage of 10kV were carried out. Our results indicate, that the process of enforcing a current decay strongly depends on the mechanical resistance of the liquids to deform under the pressure of the electric arc.

Thermal FEM Analysis of Surge Arresters During HVdc Current Interruption Validated by Experiments

This paper deals with the development of an accurate finite-element model of an arrester to investigate the electrothermal and mechanical stress during dc current interruption. The comprehensive analysis performed on a ZnO surge arrester is supported by experiments during high-voltage dc circuit breaker current interruption. The performed experimental analysis comprises three sequential 26 kV/10 kA direct current interruption tests carried out within a period of one hour. The dynamic temperature and current distribution of the surge arrester columns during current interruption are measured. The finite-element simulation results are in good agreement with the test results. The influence of the surge arrester temperature on the current distribution among the surge arrester columns is analyzed. The impact of the surge arrester temperature on ZnO electrical characteristics and mechanical stress inside the surge arrester are also investigated. The surge arrester finite-element model can be used with full success for parameter optimization of the surge arresters to prevent possible failures when dc circuit breakers performed multiple interruptions in short period of time.

Recovery of Withstanding Voltage After Direct Current Interruption Using Vacuum Circuit Breakers

The recovery characteristics of the withstanding voltage of a vacuum gap are crucial for the development of direct circuit breakers with mechanical switches. In the active-current-injection-type dc circuit breakers, a negative voltage, i.e., a voltage of polarity opposite to that of the interrupting current, is initially applied after current zero caused by the energy stored in the active-current-injection branch. Subsequently, the recovery voltage obtains the same polarity as the interrupting current, namely, it becomes positive as the capacitance around the mechanical switch is charged. In this study, the recovery characteristics of the withstanding voltage for the negative and positive polarity are measured by applying impulse voltage after the current zero of dc interruption simulating current. The recovery of the withstanding voltage for a positive impulse takes a longer time than that of the negative impulse. The recovery of the positive withstanding voltage is determined by the decrease in the temperature of the microprojections on the cathode spot edges. The postarc current analysis shows that the postarc plasma decays with time according to the power law in the time range of 1–50 <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\mu \text{s}$ </tex-math></inline-formula> after current zero. Under the dc interruptions, where the current decreasing ratio increases, the residual plasma density after current zero tends to be higher than that under ac interruptions.

Two-Dimensional Observation of Copper Atoms After Forced Extinction of Vacuum Arcs by Laser-Induced Fluorescence

The distribution and dissipation of neutral atoms are crucial for understanding the dielectric recovery process after interrupting direct current (DC) vacuum arcs. This article aims to investigate the dissipation of copper atoms after a forced extinction of the vacuum arc experimentally, adopting the plane laser-induced fluorescence method. The change in the 2-D distribution of copper atoms with time is presented. The results show that the magnetic fields, the axial magnetic field (AMF), and the transverse magnetic field (TMF) have a limited effect on the initial density of copper atoms. For both the AMF and the TMF, the copper atom densities at current zero (CZ) vary in the range (6– $8) \times 10^{17}\,\,\text{m}^{-3}$ when 3-kA vacuum arcs are forced to 0 in 0.2 ms. Contrary to the TMF case, in the AMF case, the evaporation on the anode after the CZ results in long-existing atoms near it. Consequently, the atom density of the TMF decays faster than that of the AMF, which indicates that a vacuum interrupter with the TMF contacts has a better performance when interrupting a DC load. The difference between the two magnetic fields originates from the arc control patterns. Namely, the AMF tends to keep vacuum arcs in a stable mode, which is unfavorable for a DC interruption; on the contrary, the TMF drives the vacuum arcs to move at high velocities resulting in faster dissipation of copper atoms after the CZ. In addition, the composition proportion of CuCr contacts has a limited effect on the diffusion of copper atoms when a low-vacuum arc is interrupted.

RETRACTED: Short-term dielectric recovery property of breaking for artificial zero current-limiting vacuum circuit breaker

In order to research influences of di/dt on breaking capacity of vacuum switch in the process of direct-current interruption at the time of clearance between open contacts, arc time, and current ze...

Direct current interruption with R L C circuit-convoluted arc interaction

Investigations are reported into the use of an electromagnetically convoluted arc, external to a magnetic field (B-field) producing coil, in combination with a parallel R, L, C resonant circuit for interrupting quasi-steady currents. In order to elucidate the complex interactions between the arc, B-field and R, L, C circuit, the B-field producing coil is energised independently from the current to be interrupted and the R, L, C circuit. Experimental results are presented for the time variation of the currents flowing through the arc gap, the B-field coil and the parallel R, L, C circuit, along with the voltage across the arc gap. An insight is gained into the role of various effects, which are produced by the complex interactions and which might be used to advantage for direct current interruption.(5 refs)

Switching of the vacuum-arc discharge direct current

Interruption of the direct current of a vacuum-arc discharge (VAD) is analyzed with three methods: the connection of a shunt circuit with a capacitor to the discharge chamber, the overlaying of a pulse nonhomogeneous axisymmetric magnetic field upon the discharge, and the combined action of the magnetic field and the shunt circuit. The probability of interruption of the current I = 500 A as a function of the magnetic field induction is obtained for various shunt capacitances within the range 25 ≤ C ≤ 2500 microfarad (μF). It is shown that the probability of interruption for a given magnetic field induction increases as the capacitance is raised and for the given capacitance it increases as the induction is increased. The magnitude of the magnetic system current Im to ensure the current interruption with the probability P = 1 is obtained as a function of the shunt capacitance. The impact of the shunt circuit parameters upon the arc current is analyzed. The time-domain plot of the arc current for the shunt capacitor C = 2500 μF was estimated. Its results agree with the experiment. It is shown that the combined use of the magnetic field and the capacitive shunt circuit is an effective method of VAD direct current interruption.

A fundamental approach to applying an insulated-gate bipolar transistor to current interruption in a low-voltage direct current delivery system

Summary A fundamental approach to apply an insulated gate bipolar transistor to a current interruption technique in a low-voltage direct current (DC) power delivery system is described. By considering the dependence of collector–emitter resistance on the gate–emitter voltage, a circuit configuration of circuit-breaker components was contrived to operate a DC interruption. Based on this design, a model DC circuit breaker composed of an insulated gate bipolar transistor was constructed to verify the interrupting performance of various DCs IDC under different source voltages EDC. The experimental results demonstrate that the model circuit breaker successfully decreased the instantaneous current to zero over an elapsed time and then interrupted the current. In addition, the results show that the current-interrupting time was almost constant against higher IDC and EDC. The results also verify that by adjusting the time constant of the gate–emitter voltage, the current-interrupting time could be controlled. Copyright © 2014 John Wiley & Sons, Ltd.

Current sharing between two vacuum circuit breakers in parallel operation for large direct current interruption

Current sharing between two vacuum circuit breakers in parallel operation for large direct current interruption

The Nature of Metal-Electrodes/SF6 Reactions in SF6 Decomposition Due to Direct-Current Interruption under Simulated Circuit-Breaker Conditions

The nature of metal/SF6 reactions under direct-current(dc) simulated circuit-breaker conditions has been examined in orderto explore: 1) the identity of the process(es) responsible for the differentmagnitudes of electrode consumption for various pure metals; 2)the factors determining the different rates of reaction with SF6observed for different metals. It is concluded that high-current arcerosion, which would be expected to consume the metal in the absence ofSF6, is also the primary mode of weight loss of electrodes in thepresence of SF6. The rates of reaction of the evaporated metals seem to berelated to their tendencies to attack SF6 at the sulphur "site" and not,as is generally assumed, at the fluorine "sites." Rather good correlationsare observed between the reaction rates and the heats of formationper equivalent for metal sulphides or the electrode potentials formetal/metal sulphide electrodes.