Analysis on Transient Characteristics of Neutral Point Grounding Resistor Throw-in in Flexible Grounded System
After a permanent single-phase grounding fault occurs in a flexible grounded system,the switching device of the neutral grounding resistor(a parallel small resistor)is closed with a time delay,in the hope of reliably eliminating the fault.Currently,the application effect of the protection method for the flexible grounded system based on steady-state information is difficult to meet the requirements.Moreover,there is no complete conclusion regarding the transient characteristic analysis when the small resistor is engaged,which restricts the development of the transient protection theory for grounding faults in the flexible grounded system.In this paper,a transient analysis model for the throw-in of a parallel small resistor in the flexible grounded system based on the line distribution parameters is established.The resonant characteristics among various components in the system are investigated.Based on this,a simplified model is proposed.For low-resistance and high-resistance grounding faults,analytical expressions of the transient current and voltage are provided,respectively.The variation laws of the main characteristic values such as resonant frequency,decay time constant,and maximum amplitude with system parameters and fault conditions are analyzed.And the distribution characteristics of the transient zero-sequence current of each line are also analyzed.These are compared with the transient characteristics at the fault moment at the resonant grounding stage.Finally,the correctness of the proposed simplified model for transient characteristic analysis is verified by using digital simulation and field test data.
flexible grounded systempermanent grounding faultneutral grounding resistorparallel small resistortransient characteristicprotection
万方数据
维普
