The influence of the separatrix on the stability of edge current driven external kink (peeling) modes has been studied. Two approaches have been compared: taking the limit towards the separatrix using linear ideal and resistive MHD stability codes and including the complete x-point geometry using a new resistive MHD code. A strong stabilizing effect has been observed for the ideal and the resistive peeling mode for instabilities driven by the edge current gradient. Both approaches are in good agreement. A new resistive instability remains unstable and is not significantly affected by the separatrix. This mode is a combination of a kink and a tearing type mode and could be called a peeling–tearing mode.
X-point effect on edge stability