Investigation of network protection coordination with changed reactive power flows in the future grid

Abstract:
As part of the energy transition, large thermal power plants are gradually being taken off the transmission grid and a large amount of renewable energies is being added in the distribution grids. In the future, these power systems will have to cover the high reactive power demand of the extra-high voltage grid. In this paper, the effects of an increased and changed reactive power flow on the grid protection concepts, especially distance and overcurrent relay, are investigated. To analyse the behaviour of these relays, a test grid was built up in PowerFactory™. During the studies it was discovered that both the increase and the change of the reactive power flow can lead to false tripping of the protective devices. In this context, it depends on whether inductive or capacitive reactive power is provided. Furthermore, it was found that the directional decision of the relays for this test grid is not influenced. By optimizing certain parameters, the false tripping events could be prevented.