Testing of insulation systems in accelerated aging conditions

The paper describes the testing procedure of the insulation system of electrical rotating machines with form-wound windings in accordance with the standards IEC 60034-18-31 and IEC 60034-18-42. Testing is based on a comparison of reference insulation system which has given satisfactory service experience and candidate insulation system which is intended to be used instead of existing insulation system. To prove or disprove the reliability of candidate systems in reasonable time, the accelerated aging test is carried out, considering various factors that reduce the life of the insulation system in greater or lesser extent: heat, exposure to mechanical vibrations and moisture (according to IEC 60034-18-31) and voltage (according to IEC 60034-18-42). In order to save materials and easier handling of test samples, tests are carried out on reduced models of coils (so-called formette coils) that are placed in frames imitating the stator core. The purpose of the test is to verify the potential contributions of a new impregnating resin, as well as the addition of nanoparticles in a new impregnating resin in a condition of increased voltage stress due to machine connection to the grid via frequency converter. In addition to the test procedure, the paper presents the results obtained so far.