On the Winding Insulation of Electrical Machines and its Aging Diagnostic Methods

Electrical machines are the prime mover for enormous industrial, commercial and domestic applications. These machines can be categorized on different biases: AC and DC machines according to their supply, transformers and dynamic machines such as synchronous, induction machines, and special purpose machines. Regardless of their operation working principle, they all have an essential part, which is winding. The windings in electrical machines are the main part since they are responsible on the electromagnetic field generation according to Faraday's law. Therefore, the health condition of the windings is crucial for continuous operation assurance. While it is hard to prevent electrical, thermal, mechanical, and environmental stresses, which are directly impacting the age of the windings, it is quite necessary to diagnose the insulation degradation at an early stage. Massive financial costs could be saved with the employment of a trusted diagnostic strategy. Thus, this paper aims to enlighten the recent offline and online diagnostic methods that have been used for the aforementioned purpose.