The Small Current Grounding Fault Line Selection Algorithm Research And Device Implementation

Because of its significant reliability of power supply and great equipment insulationability, small current grounding system(non-effective grounding system) is widely used inpower distribution system both in China and abroad. However, when grounding faultoccurs, accurate and fast line selection still remains a difficult technical problem due to thefact that single-phase grounding fault current of the non-effective grounding system isweak, etc. On considering that more than80%of the medium-voltage distribution linefault is single-phase grounding fault in actual production, further study on small currentgrounding line selection and development of high reliability line selecting device prossessboth theoretical and practical significance.Based on the analysis of fault features of small current grounding power system, allkinds of line selecting principles for the majority of all small current grounding fault arestudied and line selectiing criterion based on comprehensive decision which adopts themethod of single line selecting algorithm is proposed focussing on the defect of the singleline selection.In this paper, great attention on the study of resistance fault line selectionparalleled with arc suppression coil was paid according to the difference of neutral pointgrounding mode of distribution network.Furthermore, multiple steady transient lineselecting methods which hold the adventage of complementary are used in integarted lineselection aiming to improve the device reliability.Line selecting device makes a full use of the vast quantities of information from thesingle-phase grounding fault and develops meticulous utilization of every kind of faultinformation. A comprehensive line selecting method of synthesizing both quantitative andqualitative ways is proposed and adopted.The reveal of quantitative line fault degreeinformation of every possible line is designed and realized for each kind of line selectingcriterion in comprehensive method for fault line selection.In order to ensure the accuracyof line selection and the ability to adapt to various fault conditions, the comprehensiveprocess makes general evaluation of the fault degree information provided by variouscriteria and the final line selecting decision. According to the established line selecting program, a set of line selecting device isdisigned. At last, the hardware structure and software flow of the line selecting device aregiven in this paper. Based on high performance ARM chip and high speed floating-pointdigital processing DSP chip, the device mainly focuses on the design of the weak signalprocessing ability and the signal anti-jamming ability,which basically meet the lineselecting device requirement on data processing and signal acquisition. This device adoptsmodular design method which has the advantage program clarity, easy to debug, etc.