Small Current Interruption Research Articles

Research on arc root stagnation when small current is interrupted in self-excited circuit breaker

The self-excited DC air circuit breaker (SE-DCCB) has been widely used in urban rail transit due to its excellent stability. It can realize forward and reverse interruption, but has difficulty interrupting small currents due to the phenomenon of arc root sticking at the entrance of the arc chamber in the splitting process, which is known as arc root stagnation. A coupling model of the self-excited magnetic field and magnetohydrodynamics is established for the SE-DCCB with the traditional structure. The magnetic field, temperature and airflow distribution in the arc chamber are investigated with an interrupting current of 150 A. The simulation results show that the direction and magnitude of the magnetic blowout force are the dominant factors in the arc root stagnation. The local high temperature of the arc chamber due to arc root stagnation increases the obstruction effect of the airflow vortex on the arc root movement, which significantly increases the arc duration time of small current interruption. Based on the research, the structure of the magnetic conductance plate of the actual product is improved, which can improve the direction and magnitude of the magnetic blowout force at the arc root so as to restrain the development of the airflow vortex effectively and solve the problem of arc root stagnation when the small current is interrupted. The simulation results show that the circuit breaker with improved structure has a better performance for a small current interruption range from 100 A to 350 A.

A Thyristor Full-Bridge-Based DC Circuit Breaker

DC circuit breakers (DCCBs) are vital for the safe and continuous operation of large high-voltage dc grids. Insulated-gate bipolar transistor-based hybrid DCCBs (IHCBs) can interrupt currents quickly and have good operational characteristics. Thyristor-based hybrid DCCBs (THCBs) are superior to IHCBs in terms of interruption capacity because of the large surge current capacity of thyristors. Nevertheless, existing THCBs have limitations regarding one or more of the following characteristics: pre-activation, fast reclosing, quick interruption of small current and no requirement for an additional pre-charge source. This paper proposes a thyristor full-bridge-based dc circuit breaker (TFCB) with all favorable characteristics mentioned above. The TFCB contains a main conductor, a main breaker (MB), an auxiliary branch, and an energy absorber. After an interruption, the capacitor in the TFCB can restore its initial voltage quickly to guarantee that the TFCB is available for the next interruption. Quick interruption of small currents is achieved using the additional charge current provided by the auxiliary branch. Pre-activation is achieved using the conduction path in the MB. The parameter designs are analyzed to ensure that the TFCB reliably interrupts currents without damaging itself. The proposed TFCB is validated using prototype experiments and PSCAD/EMTDC simulations.

Differential Evolution Strategy for Constrained Global Optimization and Application to Practical Engineering Problems

In this paper, some modifications to the differential evolution strategy are proposed for the constrained global optimization problem. The scaling factor F is varied randomly within some range and an auxiliary set is employed to enhance the diversity of the population. The newly generated trial vector is compared with the nearest parent. The simple feasibility rule is used to treat the constraints. The effectiveness of the proposed method is demonstrated by solving some practical engineering problems. Finally, the method was applied to the robust design of a gas circuit breaker to increase the small current interruption performance

Optimal design of gas circuit breaker for increasing the small current interruption capacity

This paper describes the optimal shape design of gas circuit breaker to improve the small current interruption capability. The objective function is the minimal difference between the withstanding voltage and the applied voltage. To obtain the dynamic gas properties, the axisymmetric Euler equations are solved using the finite volume fluid-in-cell method and the withstanding voltage is calculated from the gas density and electric field intensity. The (1+1) evolution strategy is employed as the optimization tool. The optimization procedure is applied to the 170-kV gas circuit breaker model and an optimized model has considerably improved interrupting performance.

Numerical calculation of interruption properties of the self-extinguishing type SF/sub 6/ circuit breaker during small current interruption

This paper describes the gas flow properties in the arc chamber and the dielectric recovery after current zero in a self-extinguishing type SF/sub 6/ circuit breaker during small current interruption. First, employing the modified fluid-in-cell method and the movable mesh technique, the gas flow characteristic in the are chamber is calculated during the small current interruption, and secondly, the static electrical field is computed by using the finite element method. Combined with the calculation of above, this paper calculates the dielectric strength recovery after current zero and estimates the capability of small current interruption using the streamer theory of gas breakdown.

真空遮断器における小電流遮断時のアーク不安定現象

真空遮断器における小電流遮断時のアーク不安定現象

High-Voltage Low-Current Fuses and Switches

For interruption of small currents at relatively high voltages, fuses and air-break switches are most commonly employed. This paper treats of these devices which are suitable for such service as protection on the transmission lines supplying small blocks of power such as rural lines. The requirements for this service are outlined and a discussion is given of the ability of the devices to meet these requirements.

High-voltage low-current fuses and switches

For interruption of small currents at relatively high voltages, fuses and air-break switches are most commonly employed. This paper treats of these devices which are suitable for such service as protection on the transmission lines supplying small blocks of power such as rural lines. The requirements for this service are outlined and a discussion is given of the ability of the devices to meet these requirements.