Performance evaluation of ROCOF based loss of grid scheme for microgrid islanding prevention for different grid fault types near point of common coupling

Loss of grid (LOG) operation can be briefly described as a situation where a microgrid loses connection to the utility grid due to grid faults and continues to operate as an independent power island capable of feeding its own loads. Under this condition, the microgrid distributed generators (DGs) will now find their own operating voltage and frequency which may differ from the utilities´ and in some cases may go beyond the acceptable limits. This form of operation may prove to be hazardous and may be a potential threat to the power system personnel who are working on the restoration of utility lines. A Loss of Grid (LOG) protection system thus must ensure that the microgrid DGs are fully shut down and the microgrid itself is disconnected from the utility grid during entire grid fault period for islanding prevention. This paper evaluates the performance of Rate of Change of Frequency (ROCOF), LOG protection scheme, for different grid fault types near point of common coupling (PCC) in the context of islanding prevention.