Insulation

This research line is focused on the development of reliable methods for the determination of the insulation health in electric motors and generators.

The techniques usually employed in industry for the determination of the insulation condition often rely on offline tests that are aimed to measure specific parameters of the winding insulation. Among these tests, we can find: insulation resistance measurement, polarization index, dielectric absorption, capacitance, dissipation factor, HiPot tests, surge test…

These tests have some specific constraints: they should be developed while the motor is offline, so they are usually carried out during turnaround maintenance. Moreover, most of these tests only inform on the state of specific parts of the insulation (e.g. ground wall) or specific properties but cannot guarantee that all the parts of the insulation (e.g. turn insulation) remain healthy. For some other tests, expensive and complex equipment is required and there is risk of insulation breakdown (e.g. HiPot tests).

One of the few available options for the online determination of the insulation condition (i.e. while the motor is working) is the Partial Discharge (PD) analysis. PD has been successfully applied to determine how the insulation gets degraded over time and it can be applied both in an online and offline modes. However, this technique has also its own constraints, namely: more difficulty in the interpretation of the results, influence of electric noise or necessity of installation of coupling capacitors for the standard PD test. Moreover, some types of insulation failure (e.g. turn faults) are easily detectable with this technique.

In conclusion, there is a need of further research on new techniques that enable the reliable determination of the insulation condition or on the enhancement and interpretation of the currently available methods. In this context, the current research of the group is oriented toward the following topics within this line:

- Investigation of new techniques for the determination of the insulation health based on modern variants (e.g. impedance spectroscopy, advanced stray flux analysis).

- Study and assessment of the performance of offline insulation tests for a variety of motor typologies.

- Development of realistic laboratory tests that account for all the real factors influencing the insulation condition (electrical, thermal, mechanical and environmental).

- Application of pattern recognition algorithms and image processing techniques to PD data for the automatic interpretation of the results and determination of the insulation condition.

- Combination between PD and other techniques (current, flux, infrared analysis) for enhancing the assessment of the insulation condition.

Representative team projects: INSUMOT, DIMER

Most relevant publications:

1. Israel Zamudio-Ramirez; Roque A. Osornio-Rios; Miguel Trejo-Hernandez; Rene J. Romero-Troncoso; J. Antonino-Daviu. (2019) Smart-Sensors to Estimate Insulation Health in Induction Motors via Analysis of Stray Flux. Energies (12)1 – 16

2. Israel Zamudio-Ramírez, Roque A. Osornio-Rios, Rene J. Romero-Troncoso, Jose Antonino-Daviu, ““Wavelet entropy to estimate the winding insulation healthiness in induction motors”, 45th Annual Conference of the IEEE Industrial Electronics Society (IECON 2019), Lisbon, Portugal, 2019.

3. Dimosthesis Verginadis, Jose Antonino-Daviu, Athanasios Karlis, Michael. G. Danikas, “Diagnosis of Stator Faults in Synchronous Generators: Short Review and Practical Case”, XXIV International Conference on Electrical Machines (ICEM 2020), Goteborg, Sweden, 2020.