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Vacuum Circuit Breaker (VCB) consists of the main frame with the operating mechanism and the main circuits including VI (Vacuum Interrupter). Especially, a VCB for the generator protection, which is used in a power plant, requires very large contact spring force because it has to be able to withstand the high short circuit current. In order to release closing energy of VCB, the cam type mechanism...
The vacuum interrupter (VI) uses the axial magnetic field (AMF) type electrode structure to secure the current interrupting performance in long contact gaps. The AMF electrode has contact support made of stainless steel (SUS) to improve mechanical strength, but it could inevitably reduce the AMF. As a solution to increase the AMF, it is necessary to suggest a suitable geometry of contact support considering...
Three methods (series arcs, solid-state hybrid, and magnetic field enhanced arcing) for switching/interrupting DC distribution level circuits are described including advantages and limitations of each switching method. An experimental analysis of the effects of applying an external magnetic field, produced from permanent magnets, on the switching performance of a DC disconnect switch is the main focus...
Contact over-travel and over-travel spring pre-pressure are important debugging parameters of the contactor, which affect contact breaking velocity and rebound. Based on the electromagnetic mechanism of actual products, a dynamic characteristic experimental system was built to realize the adjustment of over-travel and pre-pressure and the measurement of contact breaking velocity and displacement....
To improve the interruption performance of electric switching apparatus, it is important to understand the dissipative process of injected energy between the electrodes. In this paper, the time-resolved energy balance of air arcs is investigated under various currents and gap distances. The total energy injected to the arc is divided into two parts: energy transferred to electrodes which mostly causes...
Based on magneto-hydrodynamics (MHD) theory, an air arc model is set up for the contacts and arc inducing plate at chamber inlet of a certain type of DC contactor and the dynamic behavior of the arc is simulated. The variation laws of arc length and the main conductive area migrating from moving contact to arc inducing plate were studied quantitatively under the influence of breaking speed and the...
Based on nano two-phase composite magnetic material, a design and optimization scheme of energy-saving wind power grid contactor is proposed, which solves the problems of traditional contactor's high iron loss, low speed and large AC noise. In this paper, the electromagnetic system of the contactor is redesigned by the characteristics of high remanence, high coercivity and wide hysteresis loop of...
Enhanced switching performance during the interruption process is achieved when the arc quickly enters and stays within the splitter plate region with the arc itself remaining attached to the surface of the plates. It is well known that the vent design in low-voltage switching devices (LVSDs) has a significant influence on arc motion during an interruption event: however, there has been limited experimental...
We carried out the study about temperature rise in Low Voltage switchgear on cooling systems. Ratings of this LV switchgear are 690 V, 4000 A, 85 kA and IP43. We compared the results with air cooling fan for forced cooling system and without the fan for natural convection system by numerical and experimental methods. As a result, we can obtain a calibration factor about the cooling systems on our...
This paper presents a work that was aimed to study the arc motion characteristics of low-voltage circuit breaker based on the magnetic testing technology by using hall sensors to obtain the data about the magnetic field distribution. Combined with the images of arc movement obtained by the CCD camera, the relation between magnetic field distribution and the arc motion during the interruption process...
For the requirements of low-jitter and long working-life triggered gas switches in actual conditions, the polycyclic type gas switch is designed, combining with the gas switch of three electrodes. Breakdown characteristics of trigger switches, the structure of their main electrodes and trigger electrodes are flat-polycyclic, flat-disk, and spherical-disk, are tested. The test results prove that, under...
In the coaxial spark switch conduction process, the spark discharge of trigger gap will have a certain degree of pre-ionization for overvoltage gap. In order to provide some reference for the design of coaxial switch, this paper has carried on a series of tests on the influence range and intensity of this pre-ionization. In this paper, trigger characteristics of the switch under different gas pressure...
This paper explores the magnetic inverse problem of reconstructing the current density distribution in low-voltage circuit breakers by inverting its magnetic field. The focus is on the modeling and solution phase for the stationary configuration where the effect of magnetization in splitters is considered. A new reconstruction procedure is proposed in this paper by taking the magnetization as a mapping...
Order to realize the accurate assessment of AC contactor state, point at the uncertainty of the state parameters of AC contactor and the uncertainty of which state parameters are chosen as the evaluation factors, the grey fuzzy theory is applied to state evaluation of AC contactor. Some representative information is selected as the state variable for evaluation. The weight set of each assessment factor...
Aiming at the power quality problems such as voltage sag caused by grid connection of distributed generation, this paper presents a new control scheme based on Buck-Boost transform circuit. Pulse width modulation control and adaptive closed-loop voltage feedback control are applied to the voltage on the contactor coil. The working principle and process of the system are introduced in detail and the...
Due to the characteristics of easy access, non-toxic, stable physicochemical properties and non-combustion supporting, N2 and CO2 gases attract a lot of attention of researchers as a possible substitute for SF6. Based on the gas dynamics equation, considering the collision of charged particles, the arc formation process in mixed gas circuit breaker is simulated from the microscopic point of view in...
High liquefaction temperature and greenhouse effect are two major problems of SF6. To find alternative gas of SF6 becomes an urgency in power industry. In this paper, the insulation characteristics of c-C4F8/N2 are studied. The AC breakdown voltage in slightly non-uniform electric field with different air pressure and mix ratio is measured. The results show that breakdown voltage increases with the...
An SF6 alternative gas, C4F7N mixed with CO2, has attracted great attention in recent years. The related experimental reports show that it has good insulation, thermal dissipation, switching performances and other characteristics. In theoretical research area, the thermophysical properties of plasma are of great significance to study the arc behaviour. However, for C4F7N, due to its complicated molecular...
To investigate the feasibility of replacing SF6 in gas insulated transmission line (GIL) using eco-friendly gas, the physical characteristics and dielectric strength of potential SF6 alternative gases are compared in this paper. These gases include c-C4F8-N2 mixtures, CF3I-N2 mixtures and so on. The by-products and yielding condition of these mixtures are summarized, and the thermal characteristics...
This paper reports fundamental measurement results on re-ignition process in synthetic tests for CO2 arcs in a gas blast nozzle. The synthetic test system used comprises a DC current source for an arc ignition, a half cycle AC current source, a DC current source for artificial current zero point and an impulse-like voltage source for application of quasi-transient recovery voltage (quasi-TRV). The...
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