Real-time fault detection system for large scale grid integrated solar photovoltaic power plants

•DC side faults detection of the solar photovoltaic power plants.•Using Student’s T-Test for outlier detection in photovoltaic power plants.•String level fault detection in large scale solar power plants.•Comparison of actual and simulated solar power plant for fault detection. A new fault detection system is proposed in this study for large-scale grid-tied PV power plants. The fault detection system performs string level comparison of DC power of Actual PV Plant and a simulated PV plant, referred as Theoretical PV Plant. The comparison is performed with a statistical tool which distinguishes a faulty condition and identifies the nature of the fault. This statistical tool is used as outlier detector based on the William Gosset's (Student's) T-Test. The Theoretical PV Plant generates power in a simulation tool using inputs of irradiance and PV module temperature, both obtained from sensors at the Actual PV Plant. The string power of Actual PV Plant is also obtained in the simulation from the data logger in real-time environment. These string powers of Actual and Theoretical PV Plants are compared to find a faulty condition. A GUI is developed where the fault alarms appear on Real-time Status Monitor whenever a fault occurs in the Actual PV Plant. The proposed fault detection system has been validated on a 125 kWp grid-connected PV plant.