Research Of Embedded System Based On ARM And Its Application On DC System Grounding Fault Detection

Generally speaking, it is important for safe operation of power system that DCsystem grounding fault in power plants and transformer substations is detected timelyand exactly. The detection method of low frequency signal injection, which is widelyused, is easily influenced by the capacitors between ground and each branch. As aninstrument for signal processing, wavelet transform is gradually concerned andapplied by more and more theoreticians and engineers of diversified fields for itseminent characteristic of time-frequency analysis and used broadly in power system.The former DC system grounding faulting detecting devices are mostly designedbased on SCM, which limits the using of advanced algorithms based on wavelettransform. So they couldn't solve the problems of big grounding capacitance in DCsystem. However, with the development of informationization, intellectualization andinternetization in recent years, embedded system acquires substantial room for itsdevelopment. If embedded system is applied in the DC system grounding faultingdetection successfully,its advantages of high performance, high stability and real timecould be utilized to the full, which facilitate the realization of the detection methodbased on wavelet, thereby the influence of the capacitors between ground and eachbranch could be resolved effectively.The paper presents the design of embedded DC system grounding fault detectingdevice based on ARM from three aspects. First of all, the design of the devicehardware is introduced: we should choose the appropriate MPU according torequirement of the applying field and expand the peripheral components to achievethe controls to expensive circuits for the application and realize the correspondingdetecting algorithm;in accordance with the detecting algorithm, we establish circuitsto divide and recuperate the related voltage signals to be sampled on the basis ofanalyzing the elements and characteristics of respective signals in the DC systemwhere exists grounding fault. Secondly, the design of the device software isintroduced: we port μC/OS-II to S3C44B0X and expand μC/OS-II according to theapplication requires;After deep understanding the detecting algorithm of DC systemgrounding fault based on wavelet transform of certain reference, we realize it by Cand realize the scheduled detecting flow by μC/OS-II. Finally, the realization of thedetecting algorithm is validated from two aspects: we test its reliability in PC and testits feasibility and real time in the embedded system based on S3C44B0X+μC/OS-II.The research of the paper attempts to discuss the practical applying of wavelettheory and embedded system into the detection of DC system grounding faults, whichis important to improve the safety and stability of the DC system and could providescertain help for future applications of such kind of device in the field.