Design and implementation of an Anti-Islanding Protection Strategy for distributed generation involving Multiple Passive protections

Experience with connecting farm biogas generation to rural distribution feeders has revealed that a particular costly barrier can be protection against unplanned islanding. When the size of the generation is small compared to the load on the feeder, the cost of anti-islanding protection is very small. However, once a certain size threshold is reached, alternative protection methods are required, and the standard solution in the past has been expensive utility-approved fast transfer trip. Recognizing that this would make many farm biogas projects uneconomic, the utility has agreed to work with biogas proponents to develop cheaper alternatives for projects less than 500kW. This paper describes the design of a novel Multiple-Passive Anti-Islanding Protection Strategy and its implementation on a 499kW biogas-fueled synchronous generator in Ontario.