Distributed Generation and Under Load Transformers Operation: Voltage Quality Problems and Possible Improvements

It is known that the increasing penetration of Distributed Generation (DG) implies different technical problems in the operation of distribution systems. This paper focuses the electrical Power Quality (PQ) aspects. DG can be responsible for different PQ problems, like poor voltage quality, unwanted protection trips on healthy feeders, and "islanding". Voltage quality, in particular, can become a very critical issue in a distribution system with a relatively large DG amount. The paper mainly addresses slow and fast voltage changes, and reports a case study to help understanding how under load transformers in some cases can worsen voltage quality, so as the possible remedial actions.