In this paper we discuss current knowledge of phenomena of runaway electrons in tokamaks. We summarize experimental facts and investigate theoretical understanding of runaway electrons.
We also present result of our recent work concerning influence of JET's Error Filed Correction Coils on runaway electrons dynamics. At the end of our paper we describe our plan to study runaway electrons dynamic in time and space varying magnetic field during plasma disruption as obtained from global MHD code JOREK.