Distributed energy resources - testing issues

Decentralized Energy Resources (DER) and especially wind farms became a challenge for protection, automation and control in the grids. Transmission system operators as well as distribution system operators require tests of Loss of Mains and other decoupling protection functions. In some countries certification of these functions is required. The units are equipped with a huge amount of internal protection functions as well as controls. This requires tests during commissioning or in service.
This paper figures out main strategies and approaches for protection and explains testing using current examples. It is focussing on developments in Germany with a huge amount of wind farms but also covers regulations and methods from other countries. An outlook summarizes the issues and proposes future steps.