In order to improve reliability about distributed generation access into power system, this paper provides an intensive analysis for fault characteristics of neutral-point unground based on method of symmetrical components. It presents the variation feature of voltage and current for single phase to earth, phase to phase short circuit and two-phase grounding together with transition impedance. The result is that phase to phase short circuit of neutral-point unground is the same as neutral-point grounding with neutral-point undrift. However, two-phase grounding is the same as phase to phase short circuit of neutral-point grounding with neutral-point drift. The conclusions could be applied in contingency analysis and protection setting in real distribution system within distributed generation.