Evaluation of High Voltage Rotating Machine Stator Insulation System Using Diagnostic Tests

The reliability of any high voltage equipment depends to a large extent on the insulation quality. And in high voltage rotating machines, the stator insulation is an important part with respect to the manufacturing cost as well as maintenance and lifetime aspects. During operation, insulation is subjected to one or combination of electrical, thermal, mechanical and environmental stresses. The insulation ages over time due to these stresses and eventually fails. These unexpected failures can be avoided by conducting diagnostic tests. From the diagnosis results the extent of insulation degradation can be quantified and necessary actions could be planned to avoid in-service failure of vital machines and thereby enhancing the reliability. Every diagnostic test gives a certain information about the insulation condition. In this paper, the significance of diagnostic tests are discussed and how these tests can be used to evaluate the insulation condition is presented.