Real Time Hardware-In-The-Loop Comparison of Frequency Estimation Techniques in Application to ROCOF Based Islanding Detection

Rate of change of frequency (ROCOF) is one of the most common islanding detection techniques because of its simplicity and economical benefits. However, it does need thorough considerations to avoid mis-operations of ROCOF relays during islanding. These relays operates based on frequency estimation, which is performed either from the phase voltages or by obtaining the speed measurement from generator. With the penetration of distributed generation (DG), there is high probability for unavailability of frequency measurement from a synchronous generator. This calls for frequency estimation based on network voltages and this has a significant influence on ROCOF operation performance. This paper discusses the most commonly used frequency estimation methods and summarizes the usability of these methods through real-time hardware-in-the-loop (RT-HIL) simulations for ROCOF relay.