Abstract: According to the characteristics of 35kV electrical system in a new energy field station, according to the fault record data and the protection action, the over-current trip caused by the single-phase earthing fault of two collecting lines in a photovoltaic power station is analyzed, this paper analyzes the fault development process and fault causes of the collector line, and provides suggestions for the installation, commissioning and daily operation maintenance of the electrical system of the new energy field station, so as to improve the safety of the photovoltaic power station.