Investigation of Frequency Oscillation Caused False Trips for Biomass Distributed Generation

Rate-of-change-of-frequency (ROCOF) relay is commonly used in distributed generation (DG) to detect islanding conditions. According to the field tripping records of an investigated ROCOF relay in a biomass power plant in Ontario, most of the false trips were caused by frequency oscillations. In this paper, the impact of relay parameters on the ROCOF relay nuisance trips caused by frequency oscillation disturbances is investigated. These parameters include the trip level, the measuring time window, the pickup time delay, and the trend of frequency change. The investigation was conducted using the simulation and field recorded data. In addition, the impact of DG parameters and status on the ROCOF relay performance is also studied. Finally, a set of principles is proposed to guide ROCOF relay settings to reduce the nuisance trips from frequency oscillation disturbances.