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Auto Fault Locating System and Application Techniques for Single-line to Ground Fault Selection in Middle-low Voltage Distribution Networks

Author: ZhangQingLei
Tutor: PanZhenCun
School: Shandong University
Course: Proceedings of the
Keywords: Small current grounding system Automatic positioning Injected signal Digital processing GPRS
CLC: TM862
Type: Master's thesis
Year: 2008
Downloads: 274
Quote: 4
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Abstract

Of low voltage distribution network widely used ungrounded, also known as the small current grounding way. This operating mode has the advantages of high reliability of power supply. Small current grounding system single-phase ground fault occurs, do not form a short circuit, there is no great value short-circuit current and the three-phase line voltage is still symmetrical voltage does not affect the normal work load, can continue to run for some time. However, in the event of a single-phase ground, non-ground relative to the voltage will be increased, but also intermittent arc grounding arc over-voltage, long-term operation may damage the insulation, causing serious phase fault. So, when the system single-phase ground fault, you should immediately try to make failure to eliminate that as soon as possible to find out the fault line and the point of failure, making the necessary load transfer, the ground removal of the device from the system. Weak fault current, arc instability and other reasons, the single-phase ground fault location problem has long not been a good solution, since many substations still use artificial pull path method to find fault lines and visual method to find the point of failure. This paper focuses on the distribution network single-phase ground fault automatically locate the problem. Really put into use the single-phase ground fault location only S injection. The method uses a voltage transformer injection detection signal current to the fault system to achieve fault line selection and positioning, tracking, monitoring of the injected signal path. S injection method has strong adaptability, more widely used in a variety of different distribution system, a better application. However, S injection method need to run handheld positioning detectors artificial patrol line positioning, the low degree of automation, positioning for a long time the second point of failure, which may occur in the fault location process, causing serious consequences, short-circuit fault in adverse weather conditions or complex line environment, artificial hunt unable to be applied to the scene. In order to overcome the deficiencies of the prior art described above, the development of a fixed location detector, the use of detectors communication with the host computer, instead of the artificial hand-held locator line patrol. Single-phase ground fault occurs in the distribution system, the fault system is injected into the fault diagnosis signal of the fixed location detector detects the injected signal detector test results sent to the failure to locate the computer, the use of means of communication, positioning your computer according to the distribution lines topology and different locations in the test results of the diagnostic signals, automatically calculate the single-phase ground fault section. This high degree of automation, short positioning time, high positioning accuracy. In this paper, design the diagnostic signal detector hardware circuits and software programs. To reduce the power consumption of the device, the the detector analog filtering section is simplified, the use of the software program to enhance the role of the digital filtering. In order to improve the filtering capability of the the device digital filtering part, we designed a variety of filtering process and anti-jamming process, and complete the appropriate software programming. Using solar cells as the power supply is the main way to solve the distribution outdoors does not have a power supply problem, and to ensure that the device is always working in online. The improved signal communication mode of the communication unit, the development and realization of the GPRS network communication and optical fiber communication dual communication channel. Dual communication channels to ensure the speed and reliability of the information exchange between the detector and the master. Automatic positioning system has been developed, laboratory experiments and achieved good results.

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