On interconnection transformers in distributed generation systems

The current energy crisis is a major drive to the use of all energy resources available. The sources to be connected to the electric network require electric/electronic interfaces. There are utility recommendations for the interconnection of a distributed generation (DG) system directly with the power system. An interconnection transformer is required to perform several functions. Strict specifications do not exist in this respect due to the variety of systems in use worldwide; nevertheless, there are utility recommendations. The phenomena of balanced and unbalanced ferroresonance overvoltages are presented, which can take place in several transformer connection schemes. The necessary conditions for the phenomenon are analyzed where eight transformer connections have been studied. Solutions are reached by means of employing DG that offers technical and economical advantages to both utilities and users.