The corresponding development of resonance mass beam pressure sensor in decades is introduced and a serial of theory analysis is executed. The advantages and disadvantages are studied on the resonance mass pressure sensor. Through the finite element analysis software ANSYS, the stress and strain distribution situation is obtained in this paper. Under the outside overload pressure situation, we find that the linearity of the resonance mass beam pressure sensor presents a declining situation, but in a small range. From the total performances of sensor, it still keeps a good condition. Under the 260 times of rang pressure, the sensor chip deformation is only 14.5um, which is a kind of very small deformation situation. That is to say the resonance polycrystalline silicon mass beam sensor designed here has a high reliability under the outside overload pressure situation.

Relaying protection is very important for electric system, in order to ensure electric system normal usage, the safeguard procedures are needed. The protective relaying is main and active manner. The protective relaying significance and equipment employments and maintain is analyzed in this paper, and protective relaying technology developing prospect is also introduced in this paper.

In recent years， as the load increasing gradually，problems in voltage stability of regional power network which is the terminal of power grid is serious. From the voltage stability machine rational analysis to roll out small interfering voltage stability criterion of new, and the modal method is used to determine the key nodes and areas of the system theory basis.

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The low-voltage distribution system is the key component of the electrical power system. Some analysis and research of the low-voltage distribution system is carried out in this paper, which provides some scientific basis to design the low-voltage distribution system. Firstly, the summarize of low-voltage distribution system is taken. The influence to productions and livings of low-voltage distribution system is introduced. Secondly, the mode of connection and design philosophy of low-voltage distribution system is studied in detail, especially the high-rise buildings low-voltage distribution system is concluded and summarized.