Algorithm Of Fault Line Selection Based On Multi-band Information With Weighted Process In Non-solidly Earthed Network

The detection and protection in the non-solid earthed network is difficult.The main reason is that the fault current is small and the arc is unstable.Consequently,some developed protection algorithm is unideal in the actual application.When the single phase grounding fault happens in the non-solid earthed network,it will produce a great deal of transient information.Fault line selection has some advantages by means of the transient information, which has high sensitivity and is immune to arc suppression coil.So that it gets wide application.However,in the actual application,the effect of the fault detection based on the transient information still needs further improvement.According to a lot of theoretical research and data analysis,we found that technology of fault detection has some problems and difficulties by means of transient information:①As the band of fault information is much too wide,frequency aliasing and frequency variation of system equivalent parameters in the transient fault information results in the characteristics of some fault data relaxed, unobvious,even loss,then lower reliability location.②The lack of in-depth analysis and research on some special faults(the arc earthed fault,intermittent arc grounding,the high resistance grounding developmental fault,the two-phase in two-line earthed and short-circuit fault,the two-phase ground fault,the loop network earth fault and so on)impacts the reliability of some location algorithm.The paper analyzes the transient location algorithm in detail,the analysis of the data and the theoretical research demonstrate that frequency variation phenomenon of system equivalent parameters impacts the establishment of the fault characteristics in the fault detection technology based on the transient information,and the necessity of multi-band processing in the transient information.Through the processing,system equivalent parameters is nearly constant and fault characteristics are tenable strictly in a narrow band;according to the energy distribution of the fault information component the algorithm determines the special frequency band(SFB),and show the fault location by making full use of the value and polarity information of zero modulus current in each band,and then choose accurate fault lines according to the weight coefficient that is the proportion between the band energy and the total energy.In addition,the paper focuses on the mechanism of the grounding faults (especially special grounding faults),the influence of accuracy to the fault detection,and the analysis of the new algorithm to various types of faults.And,the protection method based on energy weight transient information in the paper is analyzed and verificated by means of the data from the ATP simulation of the non-solid earthed network. After further research on the multi-band technology,the paper proposes the protection method based on energy weight transient information.The algorithm has many advantages, such as higher reliability,better self-adaptability,and strongger detection capability for some special earthed fault besides the advantage that the method based on characteristic transient information,better the original transient information protection algorithm,so the algorithm has high practical value.In addition,through the study of a large number of data(especially the special fault),we can educe that fault patterns are various;fault processes(transient processes)are complex and changeable.And only we make further research for special types of earthed fault,so as to enhance the accuracy of the detection,and it has positive significance in improving the reliability.