To solve the problem of distribution network fault line selection caused by too few frequency components and no high amplitude low frequency components in the characteristic frequency band of transient zero sequence current, an improved ensemble empirical mode decomposition (MEEMD) method is proposed. Firstly, the influence of distributed generation on line zero sequence current was considered; then, the zero sequence current after fault was decomposed into multiple frequency signals according to frequency by meemd, and the eigenmode function was obtained and the highest frequency component is extracted; finally, the line selection result was obtained by analyzing the signal waveform of the highest frequency. The basic signal was not needed in this process, so the characteristics of the obtained signal were closer to the original signal. The process of fault line selection based on meemd was described in detail, and the influence of multi scene distribution network considering distributed generation on fault line selection is discussed. The simulation results show that the method can effectively improve the accuracy of fault line selection.

In the petrochemical process, a risk monitoring and early warning system for hazardous chemicals is designed based on CPS technology to solve the problems of monitoring, identification and prediction of major hazard sources of hazardous chemicals. The system is divided into three layers: physical layer, network layer and decision layer. At the physical layer, the front⁃end hazardous chemicals data collection, data transmission and local storage are completed, and the data are classified and transmitted to the cloud server in real time. The data passes through the network layer and is identified by the decision⁃making layer for major hazard sources and early warning for hidden dangers of hazardous chemicals. Finally, the whole data is displayed. Genetic algorithm and neural network algorithm are used in the decision⁃making level for risk assessment of major hazard sources. Simulation experiments show that this method can accurately complete the risk assessment of major hazard sources of hazardous chemicals. In the laboratory, the remote monitoring and early warning system for hazardous chemicals based on CPS is proved to have the capability of hazard source identification and risk hazard prediction through actual verification.

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.

To point charge, the expression of the induced charge on the electrostatic sensor was calculated. When the point charge moved in the measurement zone, the spatial filtering velocity measuring method was obtained with the amplitude-frequency response of the probe and gate function seemed, and then, in the entire frequency range of speed measurement principle was all effective. The measurement speed expression of spatial filtering method was established with the characteristic frequency of signal spectrum analysis and this method can be used for measuring the flow velocity of the gas-solid two phase flow. The spectral characteristics were obtained with using the transition matrix of the spectral density and analyzing their spectrum segment features of the electrostatic sensor output voltage signal, and then the velocity measurement was completed by finding the characteristic frequency. The flow velocity measurement method was verified by experiment, and the scale factor and the correction factor was calibrated through experiment.

The spatial filter measurement principle of flow velocity was obtained by point charge mathematical model of the electrostatic sensor inserted, and signal cut-off frequency was acquired with “3dB” principle during real-time measuring flow velocity. Experiments prove that the spatial filter measurement velocity principle of inducement probe is feasible, and a set of experiment equipment was made-up to measure the solid phase velocity of gas-solid two phase flow, with which the spatial filter velocity may be measured in range of 25 m/s. The measured spatial filter velocity was calibrated by the correlation velocity of ring electrostatic sensor. It may be obtained from the measurement results that the deduced velocity measurement model of spatial filter method may complete measuring solid phase velocity in wider range.