Challenges on the Use of Vector Shift Relays in Distributed Generation: a Brazilian Case Study.

• Vector Shift Relay islanding detection capability versus system stability; • The need of Vector Shift Relay standardization for its secure applicability; • A Vector Shift Relay adjustment procedure for grid-tied synchronous generators; • A case study on Brazil's anti-islanding commissioning for distributed generation. The increasing electricity demand has encouraged consumers to invest in distributed energy resources and, among these, synchronous generators fed by biogas. One of the main concerns over this is the possibility of these sources feeding a section of the grid while a loss of mains, known as islanded operation. To prevent it, distributed generators must have protection devices that can identify this loss of connection. Vector Shift Relays are one of the most popular methods for island detection applied to synchronous generators. However, an increasing concern on false tripping of these relays has led the Brazilian electricity regulatory agency to ponder about their removal. In this paper, a detailed analysis of the Vector Shift Relay operation and configuration is done and a new procedure to determine the relay threshold value is proposed, considering different power-load mismatches. It is shown that this protection device is quick to detect islanding when there is a power unbalance greater than 30% but it may risk false tripping if adjusted to a lesser power mismatch. Finally, a discussion is presented to show that there are issues with correctly using this device and still complying with current standards, and further investigations are recommended. [ABSTRACT FROM AUTHOR]