Research And Implement On Small Current Fault Location System In Medium Voltage Distribution Network

Self-heal is one of the main functions to smart grid, fast fault location and detection of the power line is the basis for self-healing. In MV system, the faults are mostly single phase to ground faults and the neutral ineffectively grounded systems are adopted mostly, it is generally difficult to automatically detect the fault. After many years of research and practice, earth fault identification has succeeded in projects, and fault location off-line method has made substantial progress and has been applied, but this method required off-line, so reduced the user reliability. With the smart grid proposal and forward, on-line fault location has on the agenda.This paper deals with research on neutral point non-grounded system. At first, summarized the zero sequence current of on and off fault line, and studied the theory’s effectiveness and feasibility of zero-sequence power direction method. Subsequently, the fault location involved in key technologies and related algorithms are discussed, and designed a small current fault location new device. This device based on ARM Cortex-M3processor, uses GPS technology and software achieve frequency technology for accessing zero sequence phase of wide-area, and communicates through the GPRS network. Paper focused on the hardware and software design.Used two designed location devices, experiments were carried out on the10kV physical model. In the zero-sequence current measurement node side, compares zero sequence voltage and zero sequence current phase, through zero-sequence power direction method, accurately determine the fault location, the experimental results show that the device can better measure the zero-sequence signal, and used for single phase ground fault detection and location.Analysis of experimental results can obtained that used the location devices can be better done with simultaneous measurement signal and transmission function, and can effectively detect and locate ungrounded system single phase to ground fault, validated the effectiveness of fault location device.