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Study on Current Leakage Protection in 6kV Coal Mine Power System

Author: DongJiaQing
Tutor: GaoHouLei；PanZhenCun
School: Shandong University
Course: Proceedings of the
Keywords: The mine small current grounding system Single-phase ground fault Signal injection method Selective leakage protection device Fault Location
CLC: TM862
Type: Master's thesis
Year: 2010
Downloads: 402
Quote: 1
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Abstract


China's coal mine 6-35kV for the grid neutral non-effectively grounded (also known as the small current grounding), that is ungrounded or arc suppression coil grounding, a few ground via high resistance. Highest probability of single-phase ground fault occurs, about 80% of the total failure. Small current grounding system single-phase ground fault occurs, the fault current is very small, and the three-phase line voltage is still symmetrical, does not affect the normal power supply of the load, the system can continue to run for some time. Bring great risks due to the distributed capacitance of the cable lines than overhead lines, single-phase ground fault occurs when the arc suppression coil input is not timely, the arc or spark release will give coal mine production safety. With the distributed capacitance increases, the ground point arc can not be self-extinguishing and cause arc grounding overvoltage, and even develop into a serious systemic accident. Must immediately elect the fault line and trip the removal of the fault as soon as possible to ensure the safety of the underground. In many mines leakage protection grounding fault line selection and positioning method, the signal injection method due to the use of the information of the signal line selection and positioning, independent of the magnitude and direction of its performance and ground current, suitable for different structures of the small current grounding systems, access to a wide range of applications. The reliability and accuracy of the injection signal in the form of the signal injection (amplitude and frequency) and fault status are closely related. Therefore, the analysis of the frequency of the signal, injection and transition resistance and distributed capacitance of the accuracy of the line selection is necessary. At the same time due to communication difficulties between the special nature of the the underground protection unit installation, protection unit and the host must find a new single-phase ground fault line selection solutions. On the basis of the analysis of the basic principles of the signal injection method, and the development of a mine leakage protection device to automatically detect and complete the single-phase ground fault trip. The combined mine the actual situation to determine the principle of selecting and testing methods of the injected signal equivalent circuit, numerical analysis and system simulation of distributed capacitance and transition resistance on the signal injection method. Voltage detection signal generation module start injected signal switching control integration, The device combines core μPSD3334D management module is used to achieve fault phase judgment signal automatic and manual switching; specially designed filter the choke circuit device plays a protective role; weak signal conditions for a system into the design of high-precision analog filtering and digital filtering in order to get an accurate injection signal information; according to the principle of decentralized protection analysis, design the distance protection unit, with the injection control unit together constitute a selective coal leakage protection system. In order to verify the distance protection unit part of the effect of the injected signal detection and extraction, to build a laboratory model for testing. In the laboratory, according to the actual situation to build a simulation test system and MATLAB programming constructs test data source, the effect of the injected signal detection test. The use of a fault leakage protection device injection system in different frequency signal fault location and line distributed capacitance and insulation resistance calculations used to the insulation monitor the arc suppression coil compensation calculation. Extract supply line busbar the injected signal voltage, current, impedance method to achieve Fault Location, corrected for the transition resistance and distributed capacitance is large; PSCAD system simulation, this algorithm to calculate the amount of higher accuracy. Content that is made in this article, closely combined with the actual needs of the coal-powered systems, has some theoretical significance and a high application value.

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CLC: > Industrial Technology > Electrotechnical > High Voltage Engineering > Overvoltage and Its Protection > Over-voltage protection devices
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