Fault Line Selection Method Based on Model Identification for Flexible Grounded Distribution System

To solve the problem of fault line selection (FLS)in flexible grounding distribution system (FGDS), a method of line selection based on transient zero-sequence network model identification is proposed. The transient zero-sequence network consisting of the initial energy storage discharge of the arc-suppression coil after the neutral point small resistance is put into operation is established, and the change rule of the main frequency in the stage of transient process and the time-domain model of the transient current of the sound line and fault line are analysed. In the transient process of any sound line its transient main frequency current by the transient zero-sequence voltage first-order derivative and its own capacitance to ground linear expression, that is, the sound line is equivalent to the capacitance model; and for the fault line than the sound line to increase the transient zero-sequence voltage and the transition resistance of the linear expression of the part. The line capacitance model is further used as the reference model for identification, and the transient current of each line is calculated using the transient zero-sequence voltage and the capacitance parameter of each line itself. Theoretically, if the transient calculated current is consistent with the actual measured current, it indicates that the actual line is a capacitance model and is judged to be a sound line; conversely, it is judged to be a faulty line. The corresponding FLS criterion is further constructed using the difference between the transient calculated and measured currents. Finally, the applicability of this wire selection scheme under different transition resistances and fault locations is verified by MATLAB simulation software.