Connection of a distributed resource to 2-transformer spot network

Recent energy crisis brought about renewed interest in connecting distributed resources (DR) in spot networks of downtown metropolitan areas. Several important safety and technical constraints exist that need to be addressed by the developer and the utility. While interconnecting DR to the utility is often a complex issue, interconnecting to secondary networks is always complex and not always possible. This article highlights an approach taken for successful installation of a 75 kW DR to a spot network supplying an office building. In the subject case an indiscriminate connection of DR would have resulted in serious consequences to system integrity. The solution consisted of applying power relays for automatic supervision of the DR depending on the conditions in the system. The signals were derived directly from the network protectors ensuring full integrity of the system. Tests demonstrated that the installation performed as designed. DR is now in operation for one full year.