Applied Mechanics and Materials Vols. 143-144

Abstract: A crucial factor of the insulation strength in EHV & UHV power system is switching over-voltage, which was simulated and calculated respectively for power system of 500kV, 750kV and 1000kV in EMTP-ATP software. The calculation results show that for the 500kV power system, the both sides of which having MOA could limit the closing and reclosing over-voltage under 1.87p.u after eliminating closing resistors, and the maximal energy absorbed by MOA is 365kJ; for the 750kV power system with three arresters, after eliminating closing resistors, the switching over-voltage could be suppressed to 1.65p.u, and the maximal energy absorbed by MOA is 3360kJ; For the 1000kV power system, according to the simulation and calculation, it would be better rely on closing resistors and MOA together to limit the switching over-voltage, provided four arresters were installed along the lines, over-voltage can be suppressed to 1.34p.u., and the energy absorbed by MOA is far less than the maximal capacity of energy.

Abstract: Analysis of general mathematical model and the traditional anti-time algorithm of over-current protection for microcomputer based on the algorithm proposes look-up table and Taylor expansion. To solve the problem of c=0.02 of general anti-time in microcomputer is difficult to implement directly. This paper chooses the Taylor expansion method and selects the general anti-time and thermal over-load (no storage) anti-time for experiment. The experiment proves that the Taylor expansion method can achieve exactly the characteristics of microprocessor-based inverse time.

Abstract: In view of the present our country coal mine high-voltage power grid widely used 6kV or 10kV cable direct power supply condition. To describe a DSP-based adaptive line selection leakage protection program of high-voltage power grid. It adopts under-compensation, adaptive random tuning and phase-sensitive comparison to judge the fault branch and achieve selective leakage protection, and make the protection system more perfect and reliable.

Abstract: Compared with AC (alternating current) transmission, DC(direct current) transmission has obvious superiority at high power, long distance, submarine cable transmission and asynchronous interconnected between exchange systems etc.. This paper constructed a kind of 12 pulse bridge UHV DC transmission system that includes control protection function through MATLAB/Simulink tool. By setting the breaker parameters, this paper studied the 12 pulse bridge UHV DC transmission system AC/DC side in case of setting down time, type and cleared. The simulation results demonstrate that this system has a good effect in harmonic control and it has no power compensations in realizing HV DC process, and it can completely work as an important reference in constructing HV DC power grid.

Abstract: This paper lays the emphasis on the common methods of analysis and diagnosis on electromagnetic compatibility . Firstly it introduces the significance of fault diagnosis on electromagnetic compatibility, and then introduce methods of fault diagnosis and detection technique of fault signal. Finally, the common methods of analysis and judgment was summarized.

Abstract: To describe 6kv high-pressure explosion-proof switches, the main device of ensuring the safe operation of in coal mine power supply system, are widely used in coal mine, which can complete the mission of underground high-voltage power supply and distribution and the controlling of high-pressure water pump motor. The short-circuit of high-pressure explosion-proof switch is not a common fault, but the event usually cause a large area power outage, especially at high gas underground mine, which is a serious threat to production safety. In this paper, the analysis of switch short-circuit accident triggered by the isolating switch shows the reason of the accident, and we can summarize the relevant experiences and lessons learned.

Abstract: Microstrip Antennas have many applications in various communication systems. A new configuration of microstrip antenna is proposed in this paper. The microstrip antenna has two radiation ports. Through changing the radiation intensity of the two ports, the proposed structure breaks the balance of the radiation of the microstrip antenna therefore the radiation pattern would be changed corresponsively. Theory analysis is carried out based on microstrip antenna theory. Both analysis and simulation show that the new configuration can realize the radiation pattern controlled and the theory analysis agreed very well with simulation.

Abstract: According to high-voltage squirrel-cage AC asynchronous motor using string reactor to reduce voltage starting,there are some shortcomings such as circuit complexity, operation and maintenance trouble, the unfavorable to maintain and update and so on. Design of an intelligent explosion-proof electromagnetic starting reactor based on PIC16F887 microcontroller is proposed, this reactor has time type, current type, time-current starting type which can be set and it has temperature detection protection function in the starting process. After starting completion, it also has the bypass electrical locking function which can real-time monitor the current, voltage and temperature signals to realize intelligent. Using the reactor of controller already has been applied rated voltage 10kV, rated power 1600kW fan commissioning in a coal mine, the test results indicate that this reactor controls current smoothly in the starting process, and has reliable starting performance, easy operation, and high degree of intelligence.

Abstract: The controller of high tension anti-explosion switch in the coal mine pit is the core of the whole switch system. The headquarter of the working switch. Meanwhile, it is also the weak part in the switch cabinet. Problems are liable to cause danger to the power system in the mine pit, especially when the working environment of the supply power wire netting is not stable. The paper, based on the circuit structure and working principles of different controllers, puts forward an improved design for the controller. And the controller operates well after the experiment.