Corona protection in high voltage machines

In electrical machines from 5 kV upwards there are electrical discharges (corona manifestations) that destroy the insulating materials, which leads to the destruction of the machine. The application of so called corona protection materials helps to avoid this destructive process. The application of the corona protection materials in electric insulating technique is split up into four groups stating: 1st: outer corona protection, in the slot 2nd: inner corona protection, inside of the insulation 3rd: electrical field control on the coil head 4th: slot linings with conductive sheets The application of these materials means a remarkable increment of service life for medium voltage machines (3…8 kV) and renders actually possible the construction of higher voltage machines.