Mine hydraulic system fault diagnosis with a variety of forms can only rely on the experience and knowledge, and this restricts the application of the hydraulic system in mine equipments to a large extent. The simulation experiments were made and a new measuring and diagnosis method was proposed aiming at the phenomenon of appearing the cavitation in hydraulic system. Through the wavelet transform of the static random signal, it was found during the experimental and theoretical analysis that the process of using wavelet transform could accurately diagnose the cavitation appearing and cavitation occurs in hydraulic system of the moment, and it was a bigger help for the fault diagnosis of hydraulic system of the form by the cavitation of the oil pipe. The experimental results show that the method of hydraulic system fault diagnosis was feasible with the wavelet transform to the electrostatic signal, and the judgment was correct in about 95%.

In small current grounding system, determining singlephase grounding fault lines is quick a key question for realizing protection of power distribution net. Studies at the paper as follows was outspreads: a method of malfunction lineselection using the size and direction of zero sequence full current was advanced in neutral point indirect grounding system on the base of studying malfunction lineselection methods. Besides, a new method of lineselection using zero sequence transient electric charges for identifying singlephase grounding fault was put forward. This method is suit for neutral point to the ground via arcsuppression coil system. Computer simulation results indicate that the method has the merit of high lineselection accuracy rate and is propitious to implement microcomputer lineselection devices.