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.
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. >
D'une application pratique des indices bio-météorologiques
Abstract The purpose of the author is to determine statistically in what part of Switzerland maize could be cultivated with certain chance of rentability. The author gives first the method he used for determining the biometeorological index of four species of maize which were selected by the Swiss agronomical research stations. He has considered two possibilities for the growing period: ( a ) raising-ripening (l'approche globale); ( b ) raising-flowering, flowering-ripening (l'approche fractionee). From the biometeorological index, he calculated retrospectively the ripening time of these four species in the years 1901–1965. Assuming a priori that maize should be harvested before October 15th at the latest, he calculated, for a number of meteorological stations, the relative number of years when such conditions were fulfilled. Dividing the country in regions of similar mesoclimates and sorting these stations per region, it is possible to average the maximum altitude where maize can ripen at least 7, 8, 9 and 10 times within 10 years. Finally, taking into account the exposure and ground slope, he draws maps of the theoretically possible extension area, which maps are more reliable and detailed than the ones derived from actual means.