A real case application of ROCOF and vector surge relays for anti-islanding protection of distributed energy resources

This paper presents a case study where a Canadian utility has implemented passive anti-islanding elements as an alternative to Direct Transfer Trip to interconnect a customer-owned generator. This acceptance was done on an exceptional basis and many challenges were faced, including characterizing analytically the performance of these protection elements, developing settings and coordinating them with customer-owned protective relays. The analytical tools developed during this case study are useful to both predict the rate of frequency change and also to determine when using these passive elements are a viable and reliable alternative to active anti-islanding protection. The operation of the system under study was verified with timedomain simulations and after one year of real life operation, this system has been shown to be stable, safe and reliable.