The share of variable renewable energy resources (RES) is still rapidly increasing within the European power system. RES, which are mostly based on power electronics, replace successively conventional power plants, which alters the system characteristic and furthermore increases different challenges regarding grid congestions, voltage stability, etc. At the same time, importance of aspects regarding coupling of different sectors is increasing and provides new degrees of freedom, which have to be stronger considered during the system optimization. This session will give an overview of the approaches used in the European countries regarding the grid planning and operation tasks within the power system with high penetration of RES. The issues regarding optimal application of flexibilities, operational cascade for coordination of TSO and DSO cooperation, cross-energy system planning and operation as well as synergies between different system levels will be focused. The results of different European and national projects will be presented.