Research on acceleration phenomena with test equipment of simulating puffer type gas circuit breaker
The diagnosis was investigated by using the acceleration measurement for mechanical failure and degradation of a SF6 gas circuit breaker (GCB). The mechanical model GCB was fabricated to produce similar acceleration characteristics to a real GCB. The MEMS (Micro Electro-Mechanical System) sensor was adopted for the purpose of confirming its applicability with the well-established piezoelectric accelerometer. The acceleration characteristics of the model GCB was generally similar to the real GCB of 300kV class, except the high frequency component. The MEMS sensor application was feasible with some limitations. It was indicated a mechanical failure could be detected by the acceleration measurement.
Mechanical failure detection of circuit breakers
The mechanical condition of a circuit breaker, i.e., whether the unit is in normal or abnormal condition, has been evaluated using noninvasive diagnostics, together with signal processing and decision-making techniques. Test procedures involved obtaining vibration signals from transducers placed along the external surfaces of (and, under certain conditions, within the interior of) a circuit breaker. Using the method, quantitative assessment of a circuit breaker can be carried out for any operating condition. Tests of oil and sulfur hexafluoride circuit breakers, under both normal and abnormal conditions, were carried out. In all cases, the abnormalities was detected. >
Laminar heat or mass transfer in rectangular channels and in cylindrical tubes for fully developed flow: comparison of solutions obtained for various boundary conditions
Abstract A comparison is made of results obtained with various boundary conditions at the wall of the channels. By comparing blood Sherwood numbers for finite wall resistance with those for constant concentration boundary condition only a small variation is found for various points along the blood channel.