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Many computational techniques which could analyze the behavior of electrical arc have been utilized to estimate the interrupting ability of the circuit breakers. Among them, black-box arc model has been known for valuable tool to simulate dynamic arc-circuit interactions during fault current interruption. Previous research works has shown that the black-box model was efficient tool to analyze AC arc...
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...
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...
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...
With the development of new energy, DC system is widely applied in urban rail, ships and other fields. H2-N2 mixed gas switch has been one of the effective methods to interrupt direct circuit current for its large breaking capacity and small volume. In order to study the arc characteristics of H2-N2 mixed gas switch, a detachable interrupter is designed. The arc voltampere characteristics of H2-N2...
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...
In this paper, a novel liquid metal current limiter (LMCL) is proposed allowing for the large rated current and considerable fault current energy dissipation in DC power system. According to this topology, the LMCL consists of a fast switch and several liquid metal current limiting units in parallel. Firstly, a simulation model of this LMCL is built to calculate the fault current commutation process...
Grounding fault and injecting AC into DC control system in substation may lead to many protector problems, such as maloperation and miss trip, Based on the traditional unbalanced bridge and blocking condenser principle, the IUB(Improved Unbalanced Bridge) is put forward to detect ground resistance and alternating voltage occurred in substation DC system. The circuit of IUB models in MATLAB/Simulink...
SCF N2 may have good dielectric properties, so that it has drawn great attention from the scientists worldwide. In this paper, the rod-plate electrode model of 5mm gap with DC voltage was established, and the breakdown process of the SCF N2 was studied under the SC condition with the fluid dynamics method according to the gas-dielectric discharge principle. The results show that the breakdown voltage...
The Objective of this paper is to explore the possible decomposition pathways and products of Perfluoronitrile C4F7N by density functional theory (DFT). First, the molecular structure, vibrational frequency and energy information of C4F7N and other major molecules are calculated by Materials Studio software. These results of some species(CF3, CF2, CF, C2F4, C2F5 and so on) are in a good agreement...
Interruption property of vacuum interrupter with four different contact materials were researched by experimental method. The diameter of Wan-type contact and Spiral-type CuCr25 contact was 55mm. The diameter of Spiral-type CuCr35 and CuCr30 was 58mm. The contact thickness was 10mm before breaking test and the contact thickness was about 9mm after breaking test. The breaking current was 31.5kA and...
The objective of this paper is to determine minimum arcing interruption performance of a 126 kV single-break vacuum circuit breaker with 3/4 coil-type axial magnetic field (AMF) contacts. The full contact gap was 50 mm. A spring type mechanism was used to provide an average opening velocity of 3.0 m/s within 20 mm after contacts separation. Test duty T100s experiment with a rated short circuit current...
The controlled switching technology of a short circuit current has been proposed for a long time. However, the opening time of the mechanism used in the high voltage circuit breaker is normally tens of milliseconds and has a variation of milliseconds. The electromagnetic repulsion mechanism has a very limited variation in the opening time. It provides a potential of achieving the controlled switching...
Back-to-back capacitive bank switching is the most severe duty among capacitive current switching duties because the amplitude of the inrush current with high frequency is very large. In this paper, 36kV back-to-back capacitive current switching tests of test duty 2(BC2) were carried out with vacuum circuit breaker. And the tests were performed with a series of separate making tests of 120 operations...
Corona discharge due to a conductive particle in highvoltage system is analyzed using a coupled equation, which consists of Poisson's equation for electric field distribution and a discharge equation for space charge density variation. The charge of a conductive particle is calculated using the finite element method, and the electric force acing on the particle is obtained using the calculated result...
The arc energy has an important influence on the breaking capacity of switches. Based on the theory of magneto-hydrodynamics, a simplified two-dimensional dynamic arc model of switch is established and the variation law of arc temperature, current and arc shape are analyzed under the conditions of different breaking velocity and load characteristics. At the same time, the arc voltage, arc current...
It is acknowledged that microscopic electric field enhancement on electrode surface in vacuum interrupters (VIs) is fundamental to the electrical breakdown of vacuum gaps according to the different breakdown initiating mechanism, such as the micro-particles initiating mechanism, electric field emission initiating mechanism and so on. The objective of this paper is to investigate the characteristics...
Pre-breakdown current evaluation is of importance for Gas Insulated Switchgear (GIS) under DC high voltage application. Even if very small, assuming constant polarity of the applied voltage, such currents represent a source of charges which continuously accumulate on dielectric surfaces, especially if these have high resistance. This can lead to a significant change in the distribution of the electric...
The insulation capability is a key indicator for designing a vacuum interrupter. A vacuum discharging process, especially the initial stage of it, is correlated to the capability. However, the effect of anode is still uncertain in a vacuum discharge process. The objective of this paper is to experimentally investigate the effect of anode on the initial stage of a vacuum discharge. A ICCD camera was...
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