Papers by Keyword: Anomalous

Abstract: Commutation failure theory in HVDC transmission system is proposed and its reason is analyzed. Anomalous commutation failure phenomenon related to concurrent CF or successive CF in multi-infeed HVDC transmission system is presented. Six kinds of ac system strength are used in simulating the anomalous commutation failure, and the results show that this phenomenon is more and more serious at first as the system strength increases, and then become less serious as the strength becomes stronger. The reason of anomalous CF is found when analyzing phase A voltage with Fourier analysis in one period after fault, that is because of the major dc components and the low-order harmonics existing in voltage waves.

Abstract: Commutation failure theory of HVDC system is proposed and its reason is analyzed. Faults at inverter bus in multi-infeed HVDC system can cause local commutation failure and even concurrent commutation failure. Anomalous commutation failure is simulated with six kinds of ac system strength, and it is more and more serious at first as the system strength increases then become less serious as the strength becomes stronger. Coupling impedance is changed to get its relationship with anomalous commutation failure.

Abstract: Grinding and polishing are widely used for glass machining with fine finished surfaces. These processes result from abrasion due to repeated contacts between hard sliding particles and the glass surface. The study of contact mechanics problem is of fundamental interest to understand the process of material removal in glasses. In order to get insight into this problem, an experimental set up was designed which allows a monotonic loading of the indenter combined with a controlled sliding of the specimen to simulate a slow abrasive machining process. In addition, the experiments are conducted with an in-situ video monitoring that allows for the observation of the different fracture phenomena beneath the indenter. Fracture surfaces were also studied using SEM and AFM for multi-scale investigation. Fracture analysis was carried on a standard float glass, four different SLS glasses and a fused silica glass. The observed phenomena were discussed in the light of the influence of the normal load and the chemical composition.