Directional reactive power undervoltage protection - a protection concept for connecting decentralized renewable energy sources

With their increasing number, it is becoming important that decentralized and renewable energy sources support the stabilization of the system voltage after short voltage dropouts. Often, in the past, these generators were disconnected during network faults. This is not adequate any more, as it would lead to a considerable loss of feed-in power. However, if the generators stay connected, it must be ensured that they are not receiving reactive power, as this would lead to a collapse of the grid. In Germany, a number of legal requirements and grid codes regulate the connection of such generators. These documents also stipulate the use of Directional Reactive Power Undervoltage Protection (Q->& U< protection) that would disconnect such energy sources if they received reactive power during faults on the network. This presentation gives an overview of the legal documents and an introduction to the protection function mentioned above. The basic principle of the Q->& U< protection is explained by means of its requirements specifications. Furthermore, the presentation shows standardized test methods for evaluating the Q->& U< protection. It describes how to test the releasing functions, the reactive power direction determination and also all binary inputs and outputs that are necessary for the protection function.