Intelligent computer simulation tools for HV circuit breakers and issues related to simulation
Intelligent simulation tools are developed within the Integrated Simulation and Evaluation Environment using Visual Studio C++ and object oriented programming. Such an environment should result in huge savings in time and cost for switchgear manufacturers. Conventional k-epsilon turbulence model has been modified to take into account of steep radial temperature gradient at the arc edge with much improved results. Investigations of computational convergence and the effects of initial conditions show that solutions independent of initial arc conditions with sufficient accuracy can be achieved with the Liverpool arc model.
Interrupting Characteristics of Paralleled SF6 Circuit Breakers With a Highly Coupled Split Reactor
Paralleled high-voltage SF6 circuit breakers with a highly coupled split reactor (HCSR) could realize the function of automatic current-sharing and current-limiting. Aiming at investigating the arc characteristics of paralleled SF6 circuit breakers with an HCSR, the single-phase tests for the paralleled high-voltage SF6 circuit breakers with an HCSR were carried out, including the opening and closing–opening operations. The influence of the capacitor paralleled to one of the breaks was studied. A mathematical model was developed for the paralleled high-voltage SF6 circuit breakers with an HCSR by coupling the equivalent circuit equations into the magnetohydrodynamic (MHD) arc model through the embedded codes, laying the foundation for the further research. The variation of the short-circuit currents in the branches during the breaking process was analyzed in detail. The current-sharing and current-limiting effects are quite satisfying. The temperature distribution of both arc chambers was presented. The calculated results were in agreement with the experimental results to some extent.
Photoinduced spin-state transition of Co3+ in the layered perovskite manganite thin film
The photoinduced effect, at different temperatures, on layered perovskite manganite La1.2Sr1.8Mn1.8Co0.2O7 thin film deposited on a SrTiO3(100) substrate has been studied using a He–Ne laser (632.8 nm) with the power of output 25 mW at low temperatures. The electrical transport and magnetic properties of the film are investigated systematically in the temperature region from 20 to 300 K. The resistance shows a significant decrease at low temperatures (T<90 K) under laser irradiation, which can be interpreted in terms of the spin-state transition of Co3+ ions. The magnetic field combined with the laser is also used to detect the photoinduced effect of the spin-glass state. The time dependence of the metastable system under several applied fields was also discussed. The system has the ability to keep a persistent memory of the magnetic history imprinted in its zero-field resistance.