Vacuum Breaker Research Articles

EM simulation of vacuum breaker circuit by ANSYS

EM simulation of vacuum breaker circuit by ANSYS

Restrike characteristics of vacuum circuit breaker in its opening process under DC voltage

AbstractThe restrike of vacuum circuit breaker during the breaking process causes overvoltage and intensifies the insulation deterioration of high‐voltage equipment. To solve this problem, the vacuum breaker aging test method and the restrike characteristics are researched. A withstand voltage test platform of 40.5‐kV vacuum circuit breaker was established to obtain the effects of the contact spacing and loop and inrush currents of vacuum circuit breaker on the number of restrike, the wavefront steepness of the breakdown voltage, and the breakdown duration. The number of restrike during the breaking of vacuum circuit breaker decreased and the duration of the repeated‐breakdown arc increased with the increased contact spacing of vacuum circuit breaker. As the loop current of the test system increased, the number of restrike during the breaking of vacuum circuit breaker, the wavefront steepness of the breakdown voltage, and the duration of the restrike arc increased. As the inrush current amplitude increased during the closing of vacuum circuit breaker, the number of restrike and the duration of the repeated‐breakdown arc during the breaking of vacuum circuit breaker increased. The results provide a theoretical basis and data support for the preventive test of 40.5‐kV vacuum circuit breaker and the optimization of the withstand voltage test.

Increasing the energy of the initiating spark discharge in order to reduce and stabilize the delay time in a compact vacuum breaker

The similarity of the switching mechanisms of compact vacuum spark breakers and spark breakers with laser ignition is established at a comparable level of energy flux density in the ignition node–ionization of the residual gas by a stream of short-wave radiation and fast electrons from the cathode spot plasma or laser plasma. This mechanism allows you to effectively reduce the delay in triggering the spark gap by increasing the ignition energy. An experimental study of the advantages of using an ignition circuit with increased energy for controlling small-sized vacuum spark breakers is carried out. There is a steady decrease in the delay time of the spark gap and an increase in the level
 of delay stability. From the point of view of minimization and stability of the delay time of the spark gap, the energy investment in the formation of the initiating plasma occurs most effectively at the spark stage of the auxiliary discharge along the surface of the dielectric in the ignition node.

Minimization of the delay time and its spread in a compact vacuum breaker

The similarity of the switching mechanisms of compact vacuum spark breakers and spark breakers with laser ignition is established at a comparable level of energy flux density in the ignition node–ionization of the residual gas by a stream of short-wave radiation and fast electrons from the cathode spot plasma or laser plasma. This mechanism allows you to effectively 
 reduce the delay in triggering the spark gap by increasing the ignition energy. An experimental study of the advantages of using an ignition circuit with increased energy for controlling 
 small-sized vacuum spark breakers is carried out. There is a steady decrease in the delay time of the spark gap and an increase in the level of delay stability. From the point of view of minimization and stability of the delay time of the spark gap, the energy investment in the formation of the initiating plasma occurs most effectively at the spark stage of the auxiliary discharge along the surface of the dielectric in the ignition node.

Melting Pattern of Vacuum Interrupter Contacts Subjected to High Inrush Currents at High Frequencies

One important aspect in capacitor switching concerns the high inrush current during the energizing of the capacitor. For vacuum interrupters, it is assumed that the modification of the contact surface due to high inrush currents has the highest impact on the current breaking performance. One peculiarity of capacitor switching is the high rate of switching operations easily achieving 1000 operations in a couple of years. Two vacuum breakers were therefore operated up to 1000 times in a simple test circuit simulating the making of high inrush currents. According to standards, peak and frequency of inrush currents are 20 kA and 4250 Hz for back-to-back capacitor switching, or around 5 kA and 400 Hz for single bank switching. The range of inrush currents was extended here to peak currents up to 60 kA and frequencies up to 24 kHz. Peak current and frequency have an important impact on radius and current density of the inrush current arc, and thus on the energy deposited under the arc roots. Under the conditions prevailing here, the whole surface of the contacts exhibits a uniform melting pattern with the depth of the solidified melt being less than 1 mm after 1000 operations. It is assumed that the arc moves on the contact surface driven by the radial magnetic forces generated by this kind of contact and distributes the arc energy all over the contact surface. The inrush current integral ( <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">ICI</i> ) might be a measure of the available energy for contact melting or erosion. However, since the <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">ICI</i> has no relation to the arc current density, it is only representative for a particular melting pattern of the contact surface if frequency and peak inrush currents are varied in a limited range.

Diagnosis of Post-Arc Residual Plasma in Vacuum Breaker

The residual plasma in the gap between the anode and cathode has an important influence on the recovery characteristics of the medium after the arc current zero in the vacuum arc extinguishing chamber. A diagnostic system for post-arc residual plasma is proposed and designed to diagnose the density of residual plasma during sheath expansion. The experimental platform is built on the basis of the synthetic circuit and detachable vacuum chamber. The diagnostic system uses Langmuir probe array to diagnose the post-arc plasma density change in vacuum interrupter, which reflects the dynamic process of sheath expansion in the gap. The effect of different current sizes and contact spacing on residual plasma is discussed in this paper. The plasma densities diagnosed by different position probes are used to analyze the post-arc characteristics of vacuum circuit breakers from a micro-level. The accuracy and reliability of the diagnostic system are verified by comparing with the previous studies, which provides some reference value for the future research on the post-arc micro-characteristics of vacuum breaker.

Transient flow simulation, analysis and protection of pipeline systems

This paper investigated the problems and impacts of transient flow in pipeline systems due to pump power failure. The impact of different protection devices was presented to assure surge protection for the pipeline system. A model via Bent-ley HAMMER V8.0 Edition was employed to analyse and simulate hydraulic transients in the pipeline system, and protec-tion alternatives were studied. Surge protection included using only an air vessel, using an air vessel and two surge tanks, and employing five air ves-sels and vacuum breaker. The obtained results for pressures, heads, and cavitation along the pipeline system were graph-ically presented for various operating conditions. Using five air vessels with vacuum breaker valve as surge protection proved to be more effective and economical against pump power failure. Changing the flow density did not have a significant impact on the pressures. For protection with an air vessel; it was concluded that the value 40% of the original diameter for inlet pipe diameter of air vessel, and the value of 2/3 of original pipe diameter were critical values for the transient pressures. Cast iron pipes proved to be the best pipe material for all studied volumes of the air vessel. For protection with an air vessel and two surge tanks; as the inlet pipe diameters increased the maximum pressures in-creased and the minimum pressures decreased. Regression analyses were performed obtaining equations to predict the pressures according to the inlet pipe diameter, the area of surge tank, and the pipe diameter.

The question of specific features of overvoltages when switching parallel-connected vacuum breakers

The paper presents the results of analyzing switching overvoltages occurring with simultaneous shedding of active inductive load by vacuum breakers jointly connected to one bus. It is established that with the available spread in current choppings of vacuum breakers, the maximum overvoltage occurs on the contacts of a vacuum breaker out of the number of parallel connected ones, in which the gap is de-ionized last. It is recommended to damp any occurring overvoltages by arresters located in parallel to separate groups of breakers connected to one bus.

Study on the Mathematical Model of Vacuum Breaker Valve for Large Air Mass Conditions

The mathematical model of vacuum breaker valve is significant to the protection scheme. The more accurate the vacuum breaker valve model, the more reliable the calculation results. In this study, the application conditions of the air valve model are analyzed according to the assumptions used in the derivation, and the contradictions between these assumptions are proposed. Then, according to the different working characteristics between the vacuum breaker valve on the siphon outlet pipe and the air valve, the vacuum breaker valve model is deduced based on the modified assumptions. In the derivation process, the thermodynamic change of the gas in the vacuum breaker valve is assumed to follow the isentropic process rather than an isothermal process, and the water level in the vacuum breaker valve is considered to be changeable. An engineering case is introduced, and the results calculated according to the vacuum breaker valve model are compared with those resulting from the air valve model. The results indicate that the vacuum breaker valve model is suitable for large air mass conditions and can provide a theoretical basis for the numerical simulation and settings of vacuum breaker valves.

A Superconducting Fault Current Limiter with a Power of 16 MV A

The results of tests of a short-circuit resistive switching superconducting fault current limiter (SFCL) for dc mains with maximum voltage of 4.1 kV and rated current of 4 kA have been considered. The superconducting unit and automatic high-speed vacuum breaker are key components of the SFCL. The superconducting unit consists of eight series-parallel connected modules, each of which contains four parallel high-temperature superconducting (HTSC) tapes. The tests of the SFCL have been carried out under simulations of short-circuit current with maximum current of 20 kA (maximum rate of current rise is 2500 A/ms) at a voltage of 4 kV. The tests have shown the ability of SFCL to limit the current up to 4 kA and turn it off 5 ms after the starting the mode of current limitation. The mean temperature of a HTSC tape reached up to 190 K at a duration of current limitation of 5 ms, which is in the range of allowed temperatures (lower than 290 K). The time to restore superconductivity of SFCL after turning off the current was no higher than 0.3 s.

Investigation of cathode spot characteristics in vacuum under transverse magnetic field (TMF) contacts

With the continuous improvement of current levels in power systems, the demands on the breaking capacity requirements of vacuum circuit breakers are getting higher and higher. The breaking capacity of vacuum breakers is determined by cathode spots, which provide electrons and metal vapor to maintain the arc. In this paper, experiments were carried out on two kinds of transverse magnetic field (TMF) contacts in a demountable vacuum chamber, the behavior of the cathode spots was recorded by a high-speed charge-coupled device (CCD) video camera, and the characteristics of the cathode spots were analyzed through the image processing method. The phenomenon of cathode spot groups and the star-shaped pattern of the spots were both discovered in the experiment. The experimental results show that with the condition of TMF contacts the initial expansion speed of cathode spots is influenced by some parameters, such as the tested current, contact gap, the structure of the contact, the contact diameter, the number of slots, etc. In addition, the influence of the magnetic field on the formation of the cathode spot groups, the distribution, and the dynamic characteristics of the cathode spots were analyzed. It is concluded that the characteristics of the cathode spots are due to the effect of the magnetic field on the near-cathode plasma. The study of the characteristics of cathode spots in this paper would be helpful in the exploration of the physical process of vacuum arcs, and would be of guiding significance in optimizing the design of vacuum circuit breakers.

Nanošenje olova na ugljenični konstrukcioni čelik - poolovljavanje (homogeno)

With the development of chemical industry after the Second World War, new poly-plastics have been developed and they have changed the application of lead in various chemical processes, but there still are the elements and plants where lead is irreplaceable. Since the use of lead has been significantly reduced, the number of workers who worked with lead has been considerably reduced, so the lead processors have become the craftsmen who are disappearing, and the literature about the work with lead is very deficient, it hardly exists. In this article, it is given the practical use of lead application for the purpose of vacuum breaker pump protection by the method of homogenizationlead coating for the purpose of protection from the effects of diluted sulfuric acid. A special part of working with lead would be related to welding i.e. welding leads, but this article will not deal with this subject.

A-38 バキュームブレーカの歴史とHASS 211(大気圧式バキュームブレーカ)およびHASS 215(圧力式バキュームブレーカ)の改定

A-38 バキュームブレーカの歴史とHASS 211(大気圧式バキュームブレーカ)およびHASS 215(圧力式バキュームブレーカ)の改定

Vacuum Circuit-Breaker Parameter Calculation and Modelling for Power System Transient Studies

In this paper, a black-box vacuum circuit-breaker model is developed and its parameters are calculated. The developed model is deterministic and does not include the stochastic behavior of arc interruption. The phenomena, such as the current chopping, high-frequency current quenching capability, and rate of rise of dielectric strength are treated as deterministic and calculated using mean values. The vacuum breaker model is verified using a laboratory test setup, and simulation results show good agreement with the obtained measurements. The withstand voltage of the breaker during appearance of the voltage restrikes shows good agreement with the measurements. Moreover, the magnitude and repetitiveness of the high-frequency transients obtained in simulations are within a 10% margin when compared with measurements.

A model-based measurement method for intelligent circuit breaker with data communication

In this paper, an object-oriented information model of an intelligent vacuum circuit breaker based on its physical structure and function (service) was established to integrate the measuring information flow of field parameters, the monitoring information flow of status data, and the operating and controlling information flow. The status parameters of the intelligent vacuum breaker were detected by analysing the principles and methods based on IEC61850 and IEC62271 standards. The IEC 61850 standard repository can be extended according to the characteristics of the intelligent vacuum breaker status parameters, and the IED server model was constructed to be suitable for the vacuum breaker. A key feature of the new method is the use of a multimode fibre that is incorporated into the IED server model to transmit the status parameters from the target to the sensor. The main characteristic of the measurement method is that it exhibits real-time transmission of data collection. The model includes temperature testing of the switch contact, vacuum arc testing, detection of vacuum switch motion and primary circuit parameters testing. Furthermore, we show how the IEC61850 standard can be used to give a better insight on data communication of the data collector and intelligent circuit breaker. Experimental results showed that the feasibility of intelligent vacuum breaker status monitoring through the switching-on test. It purposes to achieve information integration and a frame communication platform for the intelligent vacuum breaker.

Penetration Behavior and Sample Quality of Hydraulically Activated Fixed-Piston Samplers

AbstractThis study presents an enhanced hydraulic fixed-piston (HNS-N) sampler that reflects a local practice. This sampler was employed at a deltaic site along with two other types of samplers: a similar hydraulic (HNS-K) type with no vacuum breaker and an oil-operated (ONS) sampler that is equipped with a vacuum breaker and is fixed at the center of a casing. The generation of a slowly but erratically increasing pressure in the hydraulic samplers often does not ensure constant speed and full penetration; thus, the pressure in these samplers was increased rapidly after the drill rods were filled with water. By contrast, the pressure in the ONS sampler was increased instantaneously. The hydraulic samplers exhibited slightly discrete penetration behavior, whereas the ONS sampler induced constant penetration. The sample qualities of the samplers are ordered based on an evaluation via two nondestructive methods and a consolidation test, as follows: ONS > HNS–N > HNS–K. The sample quality was affected signifi...

Thermohydraulic Analysis of Accident Scenarios of a Fusion DEMO Reactor Based on Water-Cooled Ceramic Breeder Blanket: Analysis of LOCAs and LOVA

Thermohydraulic analysis of postulated accidents will identify system responses to accident scenarios and aid in developing design of safety systems and strategies to prevent or mitigate accident propagation. This paper reports analyses of four accident scenarios of a fusion DEMO reactor based on water-cooled ceramic-pebble breeder blanket. The accidents analyzed, which were selected based on the previous logical accident analysis, are ex-vessel loss of coolant of the primary cooling system, in-vessel loss of coolant of the first wall (FW) cooling pipes, loss of coolant in blanket modules, and loss of vacuum. The analyses have identified thermohydraulic responses of the DEMO systems to these accidents, pressure loads to confinement barriers for radioactive materials. Effectiveness of the safety systems and the integrity of the primary and final (secondary) confinement barriers against the accidents are discussed. As for the final confinement barrier, we show for the first time that implementation of a pressure suppression system (PSS) to the cooling system vault and a vacuum breaker to the tokamak pit is effective in significantly keeping the integrity of the final confinement barrier against the ex-vessel loss-of-coolant and loss-of-vacuum accidents, respectively. As for the primary confinement barrier, we show for the first time that limitation of the number of blankets from which a helium purge gas line collects the bred tritium will be a key technical issue to prevent propagation of loss of coolant in a blanket box through the purge gas line and then suppress the pressurization of the vacuum vessel (VV). For the in-vessel loss of coolant of the FW cooling pipes, further optimization of the PSS or design solutions regarding in-vessel components and plasma control will be necessary to decrease the pressure load to the VV and ensure the integrity of the primary confinement barrier.

An imitation model of a power-supply system of oxygen-converter manufacturing to analyze switching overvoltage

This paper considers switching overvoltage that occurs in the power-supply system of oxygen-converter manufacturing when a circuit vacuum breaker is triggered. The particular features of such systems are analyzed, and a typical power supply scheme is considered. It is noted that overvoltage manifesting a highfrequency behavior can be produced as a result of the peculiarities of arc interruption in vacuum (current chopping, voltage escalation, and arc reignition). Such overvoltage negatively affects electric motors with insulation that have the lowest margin of dielectric strength. Conventional means of overvoltage protection—such as conventional spark-gapped arresters, metal-oxide surge arresters, and spark gaps—are inefficient at high-frequency overvoltage because of a sharp increase in their voltage-second characteristics at low pulse duration. This paper suggests using RC circuits as protection from such overvoltage. Their application is accompanied by quite exact simulations since an incorrect choice of their parameters can worsen the commutation process. The main particular features of construction of a simulation model to study switching overvoltage and to analyze protection functioning are considered. A depiction of the simulation model and results of simulations are also presented. The validity of the suggested model is determined.

Recovery of dielectric strength after DC interruption in vacuum

In order to investigate the influence of the electrode separation, arc time and frequency of the reverse current on the breaking capacity of vacuum breakers in a DC interrupting process, the dielectric recovery strength was measured after the interruption of a breaker. A high speed actuator mixed with a permanent magnetic actuator and a repulsion actuator was designed. And a circuit which can produce a high voltage pulse was set up to measure the dielectric recovery strength after the extinction of arcs. By the method of forced current-zero, experiments were carried out to interrupt a small DC current in a synthetic test circuit. Then the dielectric recovery strength under conditions of different electrode separations, different arc time and different frequencies of the reverse current was measured with the method of monopole discharge. The experimental results indicated that there existed a critical electrode separation in the DC interrupting process. Within this electrode separation, the dielectric recovery strength can be enhanced by increasing the electrode separation and decreasing the arc time. In addition, decreasing the frequency of the reverse current can also improve the dielectric recovery strength.

Applications and Importance of Thermostatic Air Vents and Vacuum Breakers in the Brewery: Vacuum Crushed Vessels are Unusable

Applications and Importance of Thermostatic Air Vents and Vacuum Breakers in the Brewery: Vacuum Crushed Vessels are Unusable