How to Analyze Aging Characteristics of Generator Main Insulation Based on Mechanical and Dielectric Loss

Abstract: The main insulation (stator winding insulation) of large generator is an important component of generator and its availability and remaining lifetime depend to a large extent on the conditions of main insulation. At present, the system of epoxy mica insulation is mostly used. Against the aging problem of main insulation during the running, the epoxy mica insulation material is used to carry out the aging test under the influence of electric and thermal stress or mechanical stress; a new analysis method - dynamic mechanical analysis (DMA) is adopted to measure aging characteristics of insulation materials; dynamic mechanical parameters are compared with that of dielectric loss. The DMA should be used to describe the aging characteristics of epoxy mica insulation.      

Key words: generator, dynamic mechanical analysis, dielectric loss, aging         

Introduction

The main insulation (stator winding insulation) of large generator is an important component of generator and its availability and remaining lifetime depend to a large extent on the conditions of main insulation. When the generator is running, under the combined effect of electricity, heat and stress, the insulation performance will decline gradually and finally disappears. Thus the study of aging performance for stator winding insulation material has a great significance for improving safe operation of large generator. The epoxy mica composite system is mostly adopted for main insulation of large generator. To correctly evaluate the remaining lifetime of main insulation, researches into its aging characteristics were made in many countries. But those researches are mainly based on statistics and processing of test data and fail to give convincing theoretical explanation.