Investigation of Distributed Generation Rate-of-Change-of-Frequency Relays

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Anti-islanding capability is an essential requirement for the grid connection of distributed generation (DG).**Rate-of-change-of-frequency (ROCOF) relays applied for biogas DG anti-islanding detection often subject to**nuisance trip due to grid disturbances and DG output power oscillations. clients of the RTDS Technologies Inc.**(RTDS) are facing such challenge for farm-based biogas DG projects. Frequent DG nuisance trips were**reported from RTDS's customers in the past few years. To solve the problem, this project will analyze reasons**of DG trip events and provide solutions, based on historical field measurements collected from the Schouten**Cornerview Farms located in Ottawa.**The islanding detection approaches based on DG frequency variation have been recognized as the most**reliable option by industry and as a representative of these methods, ROCOF relays have been widely used in**DG applications. However, nuisance trips of ROCOF relays often happened in the fields, and DG frequency**oscillation is one of the main reasons leading to such false operations. One way to avoid nuisance trips is to set**reasonable parameters for ROCOF relays. The parameters such as trip threshold, waveform measuring window,**operation time delay, etc., will affect ROCOF relay responses.**The project includes the activities of system modeling, theoretical analysis and RTDS simulation analysis,**and optimal ROCOF relay setting design. RTDS will work in collaboration with the research team of Carleton**University to analyze the impact of grid disturbances and ROCOF relay parameters on DG nuisance trips and**propose guidance on setting ROCOF relays. The findings of the research work will help to determine optimal**ROCOF relay settings for DG anti-islanding protection and significantly reduce the unnecessary DG trips.**Essentially, the project will be beneficial for utility companies, DG owners and DG consulting companies to**act in a coordinated and proactive manner to ensure the successful adoption of biogas DG in Canada.