Enhancement of the inspection of polymeric insulators by digital infrared image processing

Summary

The main reasons for the occurrence of outage in electrical systems are associated to the failures in the electrical insulation. Specifically, in transmission systems, electrical insulation is basically achieved by using an equipment known as insulators. The power generating, distributing and transmitting companies constantly seek for predictive techniques that indicate the appropriate time to perform maintenance intervention, in order to provide services with greater quality, reliability and safety. This paper evaluates the degradation of the insulators using the monitoring of the temperature, in order to help in the indication of the most appropriate moment to perform maintenance actions. The analysis of the temperature variation along the insulator through thermography can be one of the most effective methods of evaluating insulators in service, for it considers the combined effect of pollution, electrical stress, internal defects and environmental conditions. However, analyses based only on visual inspection of images are difficult (are not enough). In fact, only specialized engineers are able to make correct judgments. In this research, a computational routine was developed, based on the digital image processing for identification, by signal expansion technique and equalization of histograms, and segmentation of insulators in thermographic images. The digital processing of the thermographic images is used to obtain the temperature values that indicate the thermal behavior of the insulators under inspection. Laboratory tests were performed with 230 kV polymeric insulators with different levels of degradation in order to capture images using an infrared radiation detection camera. The results demonstrate the efficiency of the digital thermographic imaging technique to obtain the thermal profile of the insulators inspected. Based on the products of the digital processing of the thermographic images, we have a better evaluation of the degradation levels of the insulators, besides efficiently support to the classification of the operational states of the insulators. Such computational routine can be used to minimize the subjective factor (i.e. experience of inspector) when determining the degradation level visually.

Additional informations

Authors

Da Costa, HADJI, ETIENNE LEMAIRE, NACER, MOULAI, Gonçalves

Keywords

Polymeric Insulators, Thermography, Image Processing, Degradation Analysis.