Frequency spectrum characteristic analysis of single-phase ground fault in a Petersen-coil grounded system

This paper theoretically analyzes the frequency spectrum characteristics of the single-phase ground fault in a Petersen-coil grounded distribution network. Different equivalent circuits are analyzed for faults with low transition resistances and with high transition resistances, separately. The analysis concludes that the system makes a transition from an under-damped state to a damping state, and finally to another under-damped state with the increase of transition resistances. A distribution network model is built with PSCAD/EMTDC. Simulations are performed for different fault locations, different fault initial angles, different transition resistances and different cable proportions. The analysis in time domain and frequency domain is performed. Results show that the use of cables enables the main frequency of the fault current move towards lower frequency. Meanwhile, the amplitude of the fault current obviously increases due to the high capacitance to ground of cables. The transition resistance makes the biggest influence on the characteristic frequency band. Fault location mainly affects the zero sequence current main frequency amplitude. The further the fault location is away from the Bus, the little the amplitude of high-frequency component is. The transient capacitive current component increases, the transient inductive current component decreases and the high-frequency component amplitude increases with the increase of fault initial angles.