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 Wavelet Analysis
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. Power monitoring technique is an effective method for identifying tool states. However, it is difficult to distinguish sources which led to the power signal drop. In order to solve the problem, wavelet transform algorithm was adopted to define inflexion of power signal, and wavelet threshold denoise technique was used to separate the characteristic inflexion of power signal. The simulation results show that the method is capable of detecting the cutting condition effectively.
A new power measuring circuit using a bridge-connected magnetic circuit and another magnetic core
The authors describe the operating characteristics of an oscillating circuit using a bridge-connected magnetic circuit and another magnetic core. A square-shape output voltage is obtained in the oscillating circuit. The pulsewidth in positive and negative half cycles of output voltage changes with the current of the U-form core windings and with the signal voltage applied to the exciting windings. The mean value of the output voltage varies in proportion to the product of the current and the signal voltage. Utilizing this feature, an application of the oscillating circuit to a novel power measuring circuit of simple construction is presented. >