Single-Phase-to-Ground Fault Selection And Location Method For Distribution Network Based On S-Transform

The distribution network is the end of the power system and is directly connected to the power user.The reliability of the distribution network power supply plays an important role in enhancing the social and economic benefits.Grounding fault is a common fault that affects the reliability of distribution network power supply,and its action mode is related to the grounding point of distribution network.At present,most of China's medium voltage distribution network use small current grounding,when the single-phase ground fault occurs,how to quickly and accurately determine the ground fault line and to achieve fault location to ensure safe and reliable operation of the distribution network has important research value.The electrical characteristics of the small current grounding system after single-phase-to-ground fault are analyzed in detail.The transient characteristics of the single-phase ground fault in the arc-suppression coil grounding mode are analyzed emphatically.And the transient capacitance current,the inductor current and the ground inductor current was analyzed theoretically.On the basis of this,the zero-sequence current of the fault is detected by real-time and the energy function is constructed after S-transform.The maximum energy of the line under the characteristic frequency is used as the fault selection criterion.The reliability of the theoretical analysis and the reliability of the line selection method are verified by constructing MATLAB simulation.In order to solve the problem of the traveling wave transient in the distribution network,the influence of the noise on the traveling wave calibration is analyzed in detail.The fault traveling wave data are filtered by mathematical morphology,and the wavelet transform is used to calibrate the time when the traveling wave arrives at each detection point.The reliability and accuracy of the method are verified by the simulation in the noise environment.The iterative ranging formula based on zero-mode detection wave velocity and modulus traveling wave propagation time is susceptible to environmental and simulation parameters,which leads to the problem of fault location.Based on the analysis of the zero-line traveling-wave propagation characteristics,the zero-mode wave velocity is obtained by using the information fusion at both ends.According to the single-end positioning principle of the time difference in the traveling wave,.The validity and reliability of the theory and method are verified by constructing simulation.