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. >
Effects of reservoir volume on performance of pulse tube cooler.
A pulse tube cooler has the advantages of long-life and low-vibration over conventional cryocoolers such as G-M and Stirling coolers because of the absence of moving parts at low temperature. On the other hand, the combination of a reservoir and orifice is indispensable to optimize the performance of pulse tube coolers. In order to make the pulse tube cooler compact for practical applications, the volume of reservoir should be minimized. This paper analyzes the effects of the reservoir volume on the thermodynamic performance of various components in a simple orifice and a double-inlet pulse tube cooler by combining a linearized model with a thermodynamic analysis. Expressions of entropy production for those components are presented. The results show that the reservoir volume has a significant influence on the entropy production in the various components when the reservoir to pulse tube volume ratio is smaller than about 5. The ratio is important to determine the minimum reservoir volume for a pulse tube cooler. Optimum settings for a double-inlet pulse tube cooler are also discussed.