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An arc/spark detector (ASD) was developed is to early detect wire failures and insecure connections that may lead to fire in residents and commercial and industrial facilities. A detailed circuit design for ASD implementation along with prototype product is reported. The tests of ASD, which were successful in phase identification in many different arc/spark locations under different loadings, and in false alarm probability, showed the ability and capability of the state-of-the-art detector in the electric fire hazard prevention.
This paper describes the technique for detecting failure symptom of mold transformer. This study uses the vibration signal analysis method and FEM as the technique. A loading back method is constructed for experiment, accelation sensors are adhered for measurement of vibration signal. Vibration signal measured by this method is analyzed into variation trend of measurement variables by control of control variables. Magnetic field distribution of molded winding is also acquired by FEM considering the design specification and the characteristics of insulation material in conclusion the relation of results between vibration signal and FEM is studied by these methods.
Grounding impedance is changed with the frequency of the current injected into the grounding electrode. Because the lightning surge gives a broad frequency spectrum from some hundred Hz to a ㎒, frequncy dependent grounding impedance must be evaluated and should be restrained not to badly affect on human being and electronic devices. In this paper, we make a study on the development of grounding electrode whose grounding impedance is a little change in high frequency. The structure of the grounding electrode is the same as that of coaxial cable containing carbon. The frequency-dependent grounding impedance of grounding electrode is divided 수새 both inductive and capacitive behaviors. We proposed a method of determing the length of grounding electrode that offset the two behaviors and found the length of grounding electrode not changing the grounding impedance in high frequency.
Since Seoulmetro built the first line of electric railway at seoul 1974, the passengers of railway have been increased rapidly, and electric railway requires more electric power for the greater capacity of transport. It is important that we prevent the accidents related with the subway, because all systems of subway are constructed in artificial underground structure. Since the previous versions of the earth system were built to meet the old standards of the electric facility for the lightning, some accidents related with the DC earth fault are causing secondary damages to the electric equipments. So, the old grounding system must be improved, and new standards of grounding system are required. We compare the grounding systems of the domestic railway corporations and the accidents that are related with the grounding systems. And we give ideas to improve the grounding systems and present standards which are suitable to electric railway.