This paper studies the influence to phase selectors based on the phase current difference suddenly-change and the sequence component from photovoltaic plant by a regional power grid. The capacity of photovoltaic plant compared with the system capacity is very small, in the system with outgoing main transformer neutral grounding, when a ground fault occurs in outgoing transmission line, zero sequence impedance is far less than positive sequence and negative sequence impedance, the main component of the fault current is zero sequence current, so the magnitude and phase of the three-phase currents are similar, resulting in erroneous phase selection. Taking a regional grid-connected photovoltaic plant for example, phase selector models based on the phase current difference suddenly-change and the sequence component are built and tested in PSCAD / EMTDC, and simulation results show that the action performances of phase selectors are severely affected.