Analysis on Instantaneous Power During Single-Phase Earth Fault Occurred in Resonant Grounded System

In view of the non-sinusoidal characteristic appeared by fault signal during single-phase earth fault occurred in resonant grounded system,based on the theory of instantaneous power the blind failure features of accident signals are excavated to reveal the process of energy transferring along transmission line.Transient process of the system during single-phase earth fault is analyzed,and instantaneous zero-sequence power,instantaneous real power and instantaneous virtual power during the fault are derived,calculated and analyzed.Through decomposing and comparing instantaneous power in faulty line and health line before and after the fault,it is pointed out that the variation of instantaneous power in health line before and after the fault is not evident;the variation of instantaneous power in faulty line before and after the fault is evident,the instantaneous energy transmitted in the line and the energy exchanged among different phases evidently increase,especially the oscillating component,which is obtained by decomposing instantaneous power in faulty line,contains oscillating parts in different frequencies,which does not exist before the fault.An instantaneous power-based synthetic fault line selection algorithm is constructed.According to the principle that the line,whose instantaneous power varies most sharply before and after the fault,is the faulty line,the fault line selection can be realized.Simulation results show that the proposed method is available and its physical meaning is clear.