Application of out-of-step relaying for small generators in distributed generation

The recent popularity of distributed generation (DG) has caused an increasing number of small generators (rated between 100 kVA and 12.5 MVA) to be connected to the power system at the distribution level (480 V to 12.47 kV). Some utilities require that out-of-step relays be installed by the generation owner at the point of common coupling (PCC). This paper will examine out-of-step relaying practices as they apply to small generation protection. It will consider the value, purpose, and applicability and provide guidelines for setting of this type of relay when employed.