Current Zero Point Research Articles

Analysis of Characteristics of Low Voltage Circuit Breaker by External Magnetic Field

Recently, as interest in eco-friendly distributed power has increased, studies on the improvement of the performance of breakers such as DC breakers and on the reliability of existing AC breakers have been actively conducted. To improve the performance and reliability of these breakers, this paper conducted the analysis of characteristics of a low voltage circuit breaker using an external magnetic field. In this experiment, before the current-zero point, the cut-off time to improve the breaker performance is shortened and after the current-zero point, re-ignition, which is associated with reliability, is suppressed. According to the experimental results, the short-circuit characteristics before current-zero show a significant difference of 0.13 ms in the t21 section, and the dielectric recovery strength after current-zero shows a 13.3% performance improvement in the latter half of the DRV (dielectric recovery voltage) V-t curve. This result has significant meaning because it can be easily improved under the control of the external magnetic field. Hence, it can be applied to the interruption performance improvement of breakers through detailed research in the future.

저압직류차단기의 소전류 영역 차단특성과 성능향상을 위한 연구

A low voltage direct current(DC) circuit breaker is an electrical protection device that interrupts the abnormal fault currents which result from the over-loads or short-circuits in a low voltage(less than 1,500Vdc) power distribution line. Recently, as interests in renewable energy fields(such as photovoltaic and energy storage systems) have increased, research on DC circuit breakers for system protection is also being actively conducted. However, breaking the fault current in DC system is considerably difficult even small current region since the DC does not have current zero point such as in AC. When a short circuit occurs, a fault current flows between contacts of a DC circuit breaker even though they are separated by the protective control system. Arc voltage between contacts of the circuit breaker should generate as high as possible during breaking phase. High arc voltage could lead the fault current of the circuit to zero so that arc plasma is eliminated. Based on this behavior, arc extinction system of a DC circuit breaker should be designed to effectively increase the arc voltage during current interruption period. In this paper, the characteristics of DC breaking specially in small current region were confirmed through several types of current breaking experiments and result analysis, and a method to improve performance of DC breaking in small current region was presented, and experiments were carried out to verify the validity of the method.

The Modeling of the LC Divergence Oscillation Circuit of a Superconducting DC Circuit Breaker Using PSCAD/EMTDC

We proposed a superconducting DC circuit breaker that can reliably cut off the fault currents in preparation for the DC system. It consists of a superconducting element and a mechanical DC circuit breaker. The mechanical DC circuit breaker is connected in parallel with a mechanical high-speed switch, an LC divergence oscillation circuit, and a surge arrester. This provides stable cutoff operation due to the fault-current-limiting operation of the superconducting element and the artificial current zero point of the mechanical DC circuit breaker. In this paper, the operating principle of the LC divergence oscillation circuit that creates an artificial current zero point was reviewed based on the theory. We used experimental data to model the time constant of the initial fault current, the arc model generated by the mechanical high-speed switch, and the experimental equipment. As a result, the LC divergence oscillation circuit was confirmed in the simulation, and simulation modeling was reviewed based on the theoretical principle of generation.

Operation Characteristics of Mechanical DC Circuit Breaker Combined with LC Divergence Oscillation Circuit for High Reliability of LVDC System

DC systems are modernly starting to come into the spotlight again due to the carbon-neutral policy, the development of semiconductor devices for power, and the increase in digital loads. We need to prepare in advance solutions to problems that may arise from fault currents due to transients for future DC power grid models. In the case of DC, there is no current zero-point because there is no frequency. Therefore, a large switching surge is generated when the circuit breaker cuts off the fault current. The possibility of insulation breakdown is greater than that of AC in severe cases. We consider power semiconductors or superconducting current limiters as an alternative. However, DC breaking cannot be safely achieved by itself. For reliable DC breaking, mechanical circuit breakers must be used with them. Among the mechanical shut-off methods, we adopted the divergence oscillation method. It has the biggest advantage compared to other methods in that it has a simple structure by composing passive elements and can artificially create zero current. In addition, it can be applied to a power semiconductor and a superconducting current limiter to perform a high-reliability cut-off operation. In this paper, we conducted simulation analysis by configuring the DC power grid and DC cut-off system through the PSCAD/EMTDC program. Results confirmed that the application of the LC divergence oscillation circuit can reduce the cut-off time and reduce the power burden of the mechanical DC circuit breaker (MCB).

Current Limiting Characterization by Winding Types in Superconducting DC Circuit Breaker

Currently, power semiconductors (IGBT, Thyristor, etc.) are used for the stability and high reliability of DC system operation. However, we have proposed a current limiting DC circuit breaker with superconducting winding to improve the stability of the DC system. This is superior in terms of fast cut-off speed and economy of power semiconductors, and is suitable for changes to the Point to Loads DC system that will be expanded in the future. A superconducting DC circuit breaker is a model in which a superconducting current limiter and a DC circuit breaker are combined. The superconducting fault current limiter uses a superconducting wire made of GdBCO material to limit the initial fault current to lower the current level of the fault current, and the DC circuit breaker blocks the reduced fault current from the superconducting fault current limiter by configuring a mechanical cutoff switch, passive elements L, C and SPD. In this paper, this superconducting DC circuit breaker model was designed and tested by giving two variables, and the operating characteristics were analyzed. The first is the superconducting wire connection method, and the second is the power supply voltage. In addition, the initial fault current, the time when the zero point of the fault current is generated, and the time when the shutdown is completed were compared and analyzed. As a result, it was confirmed that the helical type showed a higher current limiting rate than the spiral type, and the result of reaching a fast current zero point was confirmed.

직류 차단기에 대한 Black-box 아크 모델 적용성 평가 및 아크 특성 매개 변수 비교 분석

Analyzing the arc interruption phenomena of circuit breakers, physical arc model is generally used, but its analysis and applications is complex because it requires understanding a lot of physical parameters such as thermodynamics and mathematical equations which occur during arc interruption process. But the black box model which simulate the dynamic arc behaviour and its interaction with network could be conveniently used to extract essential parameters to determine the performance of the circuit breaker. Black box arc model could represent the non-linear characteristics of the arc using differential equations based on the conductivity of the arc. In order to develop reliable DC circuit breaker which don’t have a natural current zero point, a transient analysis of the non-linear arc characteristics occurring during interruption is needed. In previous studies, black box arc models have been used to analyze AC arc characteristics, and there are few study applying it to DC circuit breakers. This paper simulates the applicability evaluation for DC circuit breakers using KEMA and Habedank black box arc models based on the actual DC circuit breaker test data sheet. Parameters of the black box arc model were determined by performing Parameter Sweep for the main factors, such as interrupting time, arc voltage, and arc time constant. As a result, the applicability of the black box arc model to the DC circuit breaker was verified by predicting the DC arc behavior, and more suitable model for the DC circuit breaker was suggested by comparing the DC arc waveforms.

Study of the Arc Interruption Performance of CO2 Gas in High-Voltage Circuit Breaker

CO2 is a possible alternative to SF6 as the interruption medium in gas circuit breakers. The arc interruption performance of CO2 is investigated in this paper, by combining the computational fluid dynamics (CFD) analysis and the Mayr arc model. The interruption processes for a high-voltage circuit breaker filled with CO2 at 0.6, 0.8, and 1.0 MPa, as well as SF6 at 0.6 MPa, are investigated, and the influence of the filling pressure on the gas flow field characteristics is analyzed. It is found that the SF6 arc has a higher arc core temperature and a smaller arc radius than CO2 arc. The arc core temperature and arc radius both decrease with the increasing the filling pressure. The mass fluxes along the axial and radial directions and toward both the nozzle side and the hollow contact side are presented and analyzed. The time constant and arc cooling coefficient at the current-zero point are calculated based on the Mayr equation. Finally, the critical values of the rising rate of the recovery voltage (RRRV) and relative di/dt are obtained. The interruption capabilities of CO2 at 0.6, 0.8, and 1.0 MPa are estimated to be about 47%, 76%, and 95% compared with that of SF6 at 0.6 MPa, respectively, with the assumption that the Mayr equation is applicable to analyze the interruption capability of different gases.

High-Speed Observation of AC Arc Plasma Superimposed Pulse Current at Current Zero Point

The use of ac arc plasma involves a problem of instability of the arc plasma at current zero point. A method for stabilizing the transferred-type ac arc plasma has been developed by superimposing a pulse current on an ac current only at each current zero point. In this paper, a high-speed observation of the ac arc plasma is carried out in order to investigate on the stabilization of the ac arc plasma by superimposing a pulse current.

$V\!{-}t$ Characteristics of Vacuum Interrupter After Large Current Interruption

Because of the contact material's evaporation and ejection of some metal particles out of the contact gap during the flow of the vacuum arc, the contact surface may exhibit some erosion after each operation of vacuum circuit breakers. In this paper, the insulation properties were investigated for vacuum interrupters with the rated voltage of about 10-kV operating voltage after short-circuit current interruption of more than 10 kA of 50-Hz current. The vacuum interrupter contacts were opened at either a current-zero point or an ac current peak. The latter involves greater arc energy at the short gap length compared with the former. After such interrupting duty, the characteristics were measured with the lightning impulse and rectangular impulse voltages as a function of polarity relative to that of the interrupting current. When the contact was opened at the current peak, the insulation properties deteriorated substantially compared with those of the new interrupter, and the polarity of the applied impulse voltage relative to that of the interrupting current has considerable effect.

Measurement of Charged Particle Current Diffused from Vacuum Arc

Particles diffused from vacuum arc can be used for thin film formation. Diffusion of particles from vacuum arc influences current breaking properties of a vacuum interrupter. For these application it is essential to clarify the behavior of particles diffused from vacuum arc at around current zero point. In this paper dependence of diffused charged particles current on the crest value of arc current before current interruption point was shown with Faraday cup in case of oxygen-free copper electrodes and CuCr (Cu:Cr=50:50) electrodes. Experimental results were as follows. Ions and electrons diffused from vacuum arc entered into the Faraday cup with pulsive and intermittent states, when vacuum arc of DC 100 A∼150 A was generated in case of oxygen-free copper electrodes. This phenomenon corresponds to the behavior of cathode spots. Electron current value was about 100 times as large as ion current value. The pulse width is about 1∼10μs. When the crest value of arc current were 2,000 A∼10,000 A in case of oxygen-free copper electrodes and CuCr (Cu:Cr=50:50) electrodes, the amount of charged particle current for CuCr before the current interruption point was larger than those for Cu. The ratios of the ion current to the electron current diffused from vacuum arc were calculated by the waveforms of electron and ion currents. The current ratios of 0∼0.02 were taken when the crest value of arc current 2,000 A∼10,000 A.

Study of DC Circuit Breaker of H2-N2 Mixture Gas for High Voltage

Global warming caused by CO2 etc. is a field where the concern is very high. Especially, automobile emissions are problem for it. Therefore, the hybrid car is widely development and used recently. Hybrid car used electric power and gasoline. So, the car reduces CO2. Hybrid car has engine and motor. To rotate the motor, hybrid car has battery. This battery is large capacity. Therefore, the relay should interrupt high DC current for the switch of the motor and the engine. So, hybrid car used hydrogen gas filling relay We studied interruption test for the research of a basic characteristic of hydrogen gas. DC current has not current zero point. So, it is necessary to make the current zero by high arc voltage and forcible current zero point. The loss coefficient and arc voltage of hydrogen is high. Therefore, we studied interruption test for used high arc voltage. We studied interruption test and dielectric breakdown test of air, pure Hydrogen, and Hydrogen- nitrogen mixture gas. As a result, we realized H2-N2(80%-20%) is the best gas.

Effect on transferred ac arc plasma stability of increasing ambient temperature and superimposing pulse at current zero point

The use of alternating current (ac) arc plasma involves a problem of instability of the arc plasma at current zero point. This paper describes the effects of ambient temperature and of superimposing a pulse current on stability of the ac argon arc plasma; the pulse current (10 A) is superimposed on an ac current only at each current zero point. The ac arc plasma is generated between a tungsten electrode of a plasma torch and a copper counter electrode in a chamber. The ac current is 100-500 Arms and the arc plasma length is 40 mm. As the ambient temperature increases from 300 K to 900 K, the stored energy in the arc plasma increases and the required supply voltage to stabilize the arc plasma decreases by about 20% (from 270 to 220 Vrms). Additionally, superimposing a pulse current on an ac current causes the required supply voltage to decrease by about further 20% (from 220 to 180 Vrms).

電流零点パルス重畳法による移行形交流プラズマの安定化

電流零点パルス重畳法による移行形交流プラズマの安定化

Quantum mechanical effects of a nondissipative mesoscopic capacitance coupling circuit with source

The charge and current quantum zero-point fluctuations in a squeezed vacuum state of a nondissipative mesoscopic capacitance coupling circuit with source are given. The quantum noise of this circuit at absolute zero temperature is derived. It is found that there is a squeezing effect in this coupling circuit.

Quantum mechanical effects of a mesoscopic circuit

The charge and current quantum zero-point fluctuations of an active RLC circuit with squeezed vacuum state are given, and the quantum noise of this circuit at absolute zero temperature is derived.

Analyses of Axial Energy Distribution in Decaying Arc of SF6 Gas Circuit Breaker

Adopting a transient arc analyzing program, the authors analyzed the axial distribution of arc characteristics near the current-zero point, proving that while almost all portions of total arc resistance were shouldered in downstream arc, zero conductivity was achieved in the nozzle throat arc. It was also proved that in the presence of transient recovery voltage (TRV) with initial fluctuations, such as initial TRV (ITRV), an interruption was accomplished by combined effects of the downstream and the nozzle throat arc.

Stabilization of Bank Selection in No-Circulating Cycloconverter by Means of Reliable Current-Zero and Current-Polarity Detection

A new method is presented of detecting the output current zero-point and polarity in a no-circulating cycloconverter (NCC) of the continuous current type. Reverse polarity characteristics of series thyristor-diode networks are used for this purpose. This method, which assumes an inductive load, is based on the following principles. 1) When a reverse voltage is suddenly applied to the circuit, the voltage drop at the diode terminals becomes almost equal to the impressed voltage at that instant and then decays to zero gradually. (2) When the series circuit is reverse- biased and a positive polarity trigger pulse is applied to the thyristor gate, almost all of the biasing voltage appears across the diode terminals at the triggering instant before decaying to zero.

Current Zero Point Detection in Noncirculating Cycloconverter Based on Dynamic Characteristics of Thyristor-Diode Series Circuit

We have presented a new detection principle of output current zero point in noncirculating cycloconverter(NCC) on the assumption of induction or synchronous machine drives. It is based on difference of reverse recovery characteristics between thyristor and diode in series connection, and zero point is detected by means of reverse voltage impressed at diode terminals. This paper investigates the detection characteristics in more detail. Combinations of thyristor and diode affect the voltage in fairly large degree. When the voltage is impressed, thyristor connected to the diode in series has already been in off state. Snubber circuit removes the restriction imposed on the combinations.