External diagnosis of Gas Circuit Breaker contact wearing
The internal inspection for a GCB (gas circuit breaker) is regularly performed to check and change contact parts in the case that the number of times of fault current breaking reaches a specified number, because TBM (time based maintenance) criteria is generally applied. Our new system, however, can change maintenance criteria to CBM (condition based maintenance). Current interval for internal inspection may be, however, redundant compared with the actual amount of contact wearing, because it is difficult to estimate the actual amount of contact wearing correctly from the outside. Then, in order to evaluate the precise amount of contact wearing from the outside, we developed a sophisticated system which can presume the accurate amount of contact wearing by using real breaking current and arcing time. Furthermore, this new system can evaluate the precise amount of contact wearing even if CT (current transformer) is saturated by DC in fault current and regardless of the current phase at the breaking. Therefore, the internal inspection period to replace contact materials can be extended up to nearly three-fold length compared with the traditional way.
Abstract—time Base Maintenance (tbm) Is Conventionally
applied by the power utilities to maintain circuit breakers (CBs), transformers, bus bars and cables, which may result in under maintenance or over maintenance. As information and communication technology (ICT) industry develops, the maintenance policies of many power utilities have gradually changed from TBM to condition base maintenance (CBM) to improve system operating efficiency, operation cost and power supply reliability. This paper discusses the feasibility of using intelligent electronic devices (IEDs) to construct a CB CBM management platform. CBs in power substations can be monitored using IEDs with additional logic configuration and wire connections. The CB monitoring data can be sent through intranet to a control center and be analyzed and integrated by the Elipse Power Studio software. Finally, a human-machine interface (HMI) of supervisory control and data acquisition (SCADA) system can be designed to construct a CBM management platform to provide maintenance decision information for the maintenance personnel, management personnel and CB manufacturers.
Phase formation during mechanical alloying in the Ti–Si system
Abstract Mechanical alloying of Ti–Si powder mixture or TiH 1.924 –Si powder mixture was performed by high-energy ball milling, in which the Ti to Si mole ratio was 1:2. The phase formations in both mixtures during milling were investigated by X-ray diffraction. Mechanical alloying a mixture of elemental powders led to the formation of TiSi 2 equilibrium compound, while when starting from Si + TiH 1.924 , a metastable phase was formed. The metastable phase completely transforms to TiSi 2 when the mechanically alloyed powder is annealed at temperatures above 800 °C. Two different pathways of phase transitions during mechanical alloying are attributed to the existence of hydrogen atoms, i.e., when starting from Si + TiH 1.924 compared to Si + Ti, the kinetics for the formation of the TiSi 2 intermetallic compound slows down. The kinetics related to the different phase transitions depending on the starting powder mixture are discussed.