Adaptive and Automated Distance Protection in Distribution Grids with High Distributed Generation

A well-designed protection system is an essential requirement for safe and reliable power system operation. Unselective or unsensitive tripping leads to either unnecessary outages in the power system or no isolation of the faulty part of the grid. The protection system must behave desirably for all possible states of the grid, e.g., change of power fed from the distributed energy resources and grid topology changes. In this thesis, the focus is on the infeed effect, which causes changes to the measured impedance at a distance relay location, and eventually leads to unselective zone overreaches. The estimated short-circuit current contribution is determined from the active and reactive power measurements of the distributed energy resources. A communication-based protection system for distance zones is proposed that adapts the distance polygons in an automated way, using the information from the power measurements. The proposed solution is evaluated with case studies using the power system tool pandapower. Here, the adapted and non-adapted settings are compared by creating fault events at different locations in the grid and considering the change of short-circuit contributions from the distributed energy resources. It is shown that the expected tripping is achieved for all the cases where adaptation of settings is required.