Post-arc Current Measurements Research Articles

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.

Experiment research of post-arc current and cathode spots distribution in medium-high frequency vacuum arc

In this paper, the breaking process of the vacuum circuit breakers is briefly described, and the main factors that influence the post-arc process are analyzed. Based on the detachable vacuum interrupter, the experimental platform of AC breaking is built, and the experiments of the post-arc current measurement and cathode spot observation are completed. The voltage and current during the period of current zero are measured, and the images of cathode spots during the arcing process are obtained. The experimental results show that at the same frequency, the post-arc current Ipac and the post-arc charge Qpac increase with the increase in didtcz(didt at current zero). Under the same conditions of didtcz, Ipac and Qpac decrease with the increase in frequency, but both are unchanged with frequency when the frequency is high enough. With the increase in current frequency, the distribution diameter of cathode spots decreases under the condition of the same didtcz value. According to the characteristics of cathode spot distribution, the metal vapor density under different conditions is calculated. Comparing the calculation results of metal vapor with the experimental results of post-arc current, the concept of metal vapor ionization is put forward. An ionization process of metal vapor after the current zero crossing occurs. The ionization of metal vapor will cause an increase in the number of electrons after the current zero crossing, which affects Ipac, Qpac, and sheath growth.

Characteristics of high frequency interruption for vacuum DC breakers

Post arc current can reflect the residual plasma in the electrode gap and the zero zone characteristics, so it has a great influence on the interruption of the breakers. In this paper, a permanent magnet-repulsive force hybrid actuator is designed, and the post arc current measurement system is established. Based on the forced current zero method, a series of high frequency DC interruption experiments are carried out in the synthetic test circuit with vacuum interrupters. The influence of the commutation frequency and recovery voltage on the vacuum DC interruption is investigated. The results show that a short lag phase about 80 ns exists between the post arc current and recovery voltage. High commutation frequency leads to the rise of the post arc current, which is disadvantageous for the vacuum DC interruption. The post arc current also rises with the increase in the recovery voltage. The interruption is not just affected by the di/dt and du/dt. In this study, failing interruption at the first current zero happens when the transient recovery voltage is near 2800 V. The current chopping occurs easily at high commutation frequency. And the chopping current value is proportional to the commutation frequency, which is up to 120 A at 4.0 kHz.

Post-arc current measurement based on current transfer characteristic

The paper proposes a novel post-arc current measuring equipment (PACME), which is composed of vacuum switch, transfer resistance, protective gap and high-precision current sensor. The principle of the measurement is based on current transfer characteristic between the vacuum switch and transfer resistance. The current-transfer model of the post-arc current measurement is established to gain the characteristic of vacuum arc conductance and the completion time of current transfer influenced by the transfer resistance, current of main circuit and the contacts opening time. The vacuum arc of PACME extinguished just before the main current approach zero while the main current is completely transferred to the transfer resistance. According to the simulation result, the PACME is designed, especially; the transfer resistance is non inductive and over current protection. The post-arc current of vacuum switch with axial magnetic field (AMF) and transverse magnetic field (TMF) contacts was measured in synthetic short-circuit test. The measuring result of post-arc current is accurate and small interference, which satisfied the post-arc current measurement of vacuum circuit breakers.

Post-arc Current Measurement in Mechanical Circuit Breakers for Hvdc Applications

Post-arc currents contain valuable information on the breaker’s performance. In this paper, the dimensioning procedure for a measurement system for such currents, based on a diode clamped shunt resistor is presented. Based on synthetic low and high power tests, the performance of a mock-up is evaluated. Finally, the post-arc current of a model gas circuit breaker, designed for use in DC applications, is measured.

Current Interruption in Low-Voltage Circuit Breakers

Low-voltage current interruption is studied in this paper in order to develop a suitable blackbox model for low-voltage circuit breakers. The electric arc will be modeled by means of electrical quantities. Accurate post-arc current measurements by a high sensitivity current probe and signal analysis techniques (Savitsky-Golay filtering) are adopted to extract information. A set of interrupting performance evaluators is proposed, and the best performing indicators are selected. Theoretical explanations provide insight in the physical processes of low-voltage interruption. The difference with the classical context of blackbox modeling in medium- and high-voltage circuit breakers is explained, based on the different relative weight of the arc voltage and voltage supply.

Reignition phenomena after high-frequency current interruption with short vacuum gaps

Based on a large number of measurements of high-frequency (HF) current interruptions in vacuum at small contact gaps (/spl les/600 /spl mu/m), the statistical reignition behavior of vacuum switching devices after a HF current zero is investigated. Three types of reignitions can be classified. Statistical evaluation of post-arc current measurements for different parameters at current zero and different HF current ignition processes gives information about the stress of the gap as a result of the transient recovery voltage after a HF current zero (HF-TRV) and the accumulated post-arc charge. Comparing post-arc current values at the beginning of the HF-TRV and at the moment of reignition reveals a production of charge carriers during the recovery interval. Possible reasons for the different types of reignitions are discussed.

Measurements and modeling in the current zero region of vacuum circuit breakers for high current interruption

Post-arc current and voltage measurements with high time resolution were carried out with industrial vacuum circuit breakers for investigating their current zero conditions and current interruption. Based on experimental results, plasma parameters were estimated by means of a modified "continuous transition model." Dielectric effects in the post-arc current zero region were detected and modeled. At lower current amplitudes (I/spl circ/<16 kA), typical post-arc currents were obtained. At higher current amplitudes, the probability of higher post-arc current charges increases without the occurrence of breakdowns. It has been shown that charge generation takes place in the post-arc current region.

Post-arc current measurement down to the ten milliamperes range

A novel post-arc current measuring shunt is described. This shunt employs parallel connected diodes to automatically insert and disconnect the measurement resistance, very close to the current zero. The realized precision and sensitivity allow reproducible measurements down to tens of milliamperes range, with about a 5 MHz bandwidth. Furthermore repetitive testing with main currents of up to 80 kA peak poses no problem with this configuration. Using this technique the authors have discovered a new type of post-arc current which can last many milliseconds without provoking circuit breaker failure. They call this the post-recovery current. >

Post-arc current in high voltage SF/sub 6/ circuit-breakers when breaking at up to 63 kA

Post-arc current measurements were made on a high-voltage SF/sub 6/ circuit breaker. A pyrotechnic device was used to protect the measurement shunt. The tests, performed at high current values between 40 and 63 kA, gave post-arc current levels of 0.5 to 2 A. Interpretation of the experimental results by the generalized Mayr model led to the determination of a set of parameters characteristic of the apparatus tested, thereby making it possible to find the test results and, in particular, to forecast cases of thermal failure.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

Post-Arc Current After High-Current Interruption in Vacuum

Detailed measurements of post-arc current in a vacuum were made. This investigation was particularly characterized by conducting post-arc current measurements following high arc currents (36 kA rms maximum). Postarc current increases with main arc current, and shows a sharp increase when the main arc current reaches certain value. The magnitude of post-arc current for each contact material differed; the descending order is Cu-Bi > Cu > Cu-W > Ag-W. Shield current was also measured to clarify the characteristics of the ion current. Cu-Bi > Cu > Cu-W > Ag-W was the descending order of measured shield current. The characteristics of post-arc current are explained by referring to those results.

Post Arc Current of Vacuum Interrupters

Detailed measurements of post arc current in a vacuum were made and the results were compared with theory. This comparative study was particularly characterized by conducting post arc current measurements following high arc current (36 kA rms maximum). Three kinds of electrode materials and two types of electrodes were used to elucidate effects of the electrode materials and the types on post arc current. Shield current was also measured to clarify the characteristics of the ion current. The characteristics of post arc current are explained by referring to those results.

Study of the effects of gas flow on the performance of gas-blast circuit breakers

Experiments were carried out at a Siemens laboratory with specially designed circuit breakers to investigate the relationship between gas flow and arc behavior for various shapes and arrangements of gas nozzles, as well as for different types of gas and pressure conditions. The current, post-arc current, and voltage measurements were supplemented by the employment of optical methods. By using a high-speed schlieren camera, it was possible to obtain valuable information on the flow characteristics and density of the gas surrounding the arc and to estimate the influence of these quantities on the arc-quenching capacity of a breaker. The interaction of the electric power system and the arc could also be taken into account by using a dynamic arc model.