Numerical calculation of the influence of the inner corona protection layer properties on the performance of the turbine generator stator coil

The ICP (inner corona protection) of the stator coil is to reduce the concentrated electric field at the corner and to release the electrical stress in the filler. With these functions the life of the coil can be extended and the tip-up values can be lowered. But the properties of itself such as resistivity and length (the distance between two high voltage touch points) also have influence on performances of the stator coil. This paper presents a method which uses numerical calculation to describe such influences. Through calculation with various resistivity and lengths, the different working conditions of ICP have been presented and its influences on the electric field and tip-up values have been demonstrated. Furthermore, according to the influence the critical resistivity and length of the ICP layer can be decided.