Structural Traces of Secondary Faults(Fractures) along the Main Faults and Their Reliability as Kinematic Indicators

Secondary/minor structures occurring along the main fault surfaces are important indicators for judging the kinematic characteristics of faults.However,many factors can lead to the formation of these structures,which results in the difficulty for rapid judgment and application in the fields.A series of secondary faults/fractures developed due to the movement of main faults are the most important and widespread phenomena in the scope of brittle deformation.The morphology of the main fault surfaces is various,and former researchers mainly discussed the structures on the main even fault surfaces. However,the fluctuation of fault surfaces is the intrinsic character of the faults,and the intersection between the main fault and secondary faults/fractures can produce a series of kinematic indicators on the main fault surfaces.Based on previous studies and our observations,i.e.the structural traces of the P,R,R',T and X shears/faults along the main faults,some indicators which are rarely reported previously,are described in the paper.Furthermore,their reliabilities are also discussed,and more practical and reliable criteria are brought forward.We suggest that the simple application of congruous and incongruous steps without knowing their exact origins should be abandoned in the fields,and several types of indicators along one fault surface should be checked with each other as much as possible.Meanwhile,the origins of some other arcuate indicators on the fault surfaces are also discussed,and new models are brought forward.

Fault Feeder Identification in Non-effectively Grounded Distribution Network with Secondary Earth Fault

Secondary earth faults occur frequently in power distribution networks under harsh weather conditions.Owing to its characteristics,a secondary earth fault is typically hidden within the transient of the first fault.Therefore,most researchers tend to focus on a feeder with single fault while disregarding secondary faults.This paper presents a fault feeder identification method that considers secondary earth faults in a non-effectively grounded distribution network.First,the wavelet singular entropy method is used to detect a secondary fault event.This method can identify the moment at which a secondary fault occurs.The zero-sequence current data can be categorized into two fault stages.The first and second fault stages correspond to the first and secondary faults,respectively.Subsequently,a similarity matrix containing the time-frequency transient information of the zero-sequence current at the two fault stages is defined to identify the fault feeders.Finally,to confirm the effectiveness and reliability of the proposed method,we conduct simulation experiments and an adaptability analysis based on an electromagnetic transient program.