Preventive maintenance of spring applying vibration diagnostic tool- a Malaysian experience
Broad ranges of spring switchgears have been extensively used in most of Malaysian substations. Condition monitoring of hydraulic and spring switchgears have been a critical problem since the conventional methods applied failed to alert prior occurrence of faults. Recent routine reports of TNB Malaysia highlight an occurrence of 20% failures over a period of 5 year. This has lead to greater loss and high expenditure in replacing these switchgears. One of the major contributing factors in failure of hydraulic switchgears is occurrence of mechanical faults, which the conventional method of monitoring failed to detect and locate. However the recent vibration testing prevents and minimizes the breakdowns due to mechanical faults. This current vibration analysis is a noninvasive diagnostic tool applied in comprehensive monitoring of HV switchgears. This method of investigation is well ventured in many countries in Europe and USA but not yet in Malaysia. TNB Malaysia is taking the stepping stone is venturing this technology in line with our objective of seeking predictive maintenance, cost effective and reliable diagnostic tool. This paper will explore in depth the possible mechanical faults that contribute to spring switchgears failures applying vibration analysis. This paper will further interpret the results of vibration testing on 118 spring switchgears 132 kV. This, preliminary study involves interpreting the vibration signal during the event of close and open only to better understand the movement of the mechanical component during operation time enabling us to distinguish which component contributes to the fault of the switchgear.
The Real-Time Monitoring Tool States Based on Cross-Correlation Detection
Monitoring of tool condition is one of the most important techniques to be developed in the automatic cutting processes as it can help to prevent damages of machine tools and work pieces. In this paper, cross-correlation detection is used as a tool, to characterize the real time power signal during cutting. Firstly, we use the Mallat algorithms to get the standard wavelet transform result from the power signal. During the detection period, we get the real time wavelet transform result on certain level through the real time wavelet algorithms. The real time wavelet result was examined by the correlation to its normal result. According to the magnitude of the correlation factors, we can make sure whether the tools work normally. The experiment results show that the method is capable of detecting the cutting condition effectively.
AN ANALYSIS OF POLYMERIC THICK-FILM RESISTORS AS PRESSURE SENSORS
Abstract The strain-sensing characteristics of thick-film polymer-based resistors printed and cured on 96% alumina are presented. Two layout configurations have been analysed: planar and sandwich. Various strain-gauge characteristics have been studied, including the mechanical and temperature-dependent properties of the polymeric films. It has been shown that the planar polymer resistors exhibit low sensitivity, comparable to that of metal-foil gauges, whereas the MRM (metal-resistor-metal) configurations exhibit similar characteristics to those of cermet thick-film MRM gauges. It has also been observed that the mechanical properties of the polymeric films are significantly poorer than those of cermet-based gauges. This degradation in performance is attributed to the epoxy/pseudo-plastic structure of the polymeric thick-film resistor layer.