Andreas Dernfalk

Diagnostic Methods for Outdoor Polymeric Insulators

Composite insulators are considered mature products and a broad range of insulator types is nowadays available, including line insulators, hollow-core insulators and apparatus insulators, for applications ranging from distribution voltages to the highest transmission voltages. This development has created a need to elaborate diagnostic methods and tools for determining the quality of composite insulators. A review on recognized insulator faults and methods for their detection is provided.

Performance and Diagnostics of Biologically Contaminated Insulators

Biological growth has been observed on insulators installed all over the world. However, so far, its impact on insulator performance is not well known. This paper summarizes a majority of the work published in the field. Based on the gathered experiences, it can be concluded that microbiological growth is unlikely to cause severe degradation of the rubber housings of non-ceramic insulators. Furthermore, it seems that the impact of growth on the insulator performance is rather low. Techniques available for detection and characterisation of growth on insulators are also described and discusses. Among those, laser-induced fluorescence (LIF) spectroscopy has been found to give good results in remote detection of micro-organisms

In-situ diagnostics of HV outdoor insulators using laser-induced fluorescence spectroscopy

A new method for remote and non-intrusive diagnostics and surveillance of high-voltage insulators and insulation materials is presented, in particular pertinent to outdoor insulation. The method is based on laser-induced fluorescence (LIF) spectroscopy. The relationship between the LIF-spectrum and different materials and surface characteristics of silicone rubber samples are studied. These characteristics include hydrophobicity, filler content and biological growth. Furthermore, real insulators that have been naturally aged have also been studied. We conclude that laser-induced fluorescence has a significant potential to become a highly useful technique for contact-free and non-intrusive monitoring of the status of insulator materials in high-voltage systems.

Techniques for estimation of biological contamination on insulators using image analysis

A new technique for measurement and characterization of biological contamination on composite insulators has been developed and investigated. The technique, based on photography and digital image analysis, has been applied to insulators partly covered by fungal growth. Different methods for estimating measures characterizing growth patterns, like covered area and remaining creepage distance, have been explored. It is shown that the developed technique for automatic insulator recognition and estimation of its position allows for non-supervised measurements to be performed outdoors. Finally, results from flashover voltage measurements on insulators with fungal growth are reported.

Remote and non-intrusive diagnostics of high-voltage insulation materials using laser-induced fluorescence spectroscopy

A new method for remote and non-intrusive diagnostics of high-voltage insulation and insulation materials is presented. The method is based on laser-induced fluorescence (LIF) spectroscopy. The relationship between the LIF-spectrum and different material and surface characteristics of silicone rubber samples are studied. These characteristics include hydrophobicity, filler content and biological growth. Furthermore, 33-kV silicone rubber insulators that have been naturally aged in a tropical environment have also been studied. We conclude that laser-induced fluorescence has a significant potential to become a highly useful technique for contact-free and non-intrusive monitoring of the status of insulator materials in high-voltage systems.

Evaluation of flashover voltage property of snow accreted insulators for overhead transmission lines, part III - 154 kv full-scale flashover voltage test of snow accreted insulators -

In December 2005, Japan experienced a major outage in Niigata Kaetsu area due to a large amount of wet snow mixed with sea-salt accreted on several transmission line insulators. To clarify the causes of the snow-induced outage and increase reliability of the networks, a 154 kV class full-scale snow test procedure to evaluate various insulator designs was developed, and artificial flashover voltage tests of snow accreted insulators were carried out. High voltage flashover tests showed that the flashover voltage of both long-rod and cap & pin insulators was decreased with the increase of snow conductivity. Also, cap & pin insulators showed significantly higher flashover voltage than long-rod insulators. Thus substitution of long-rod insulators with cap & pin insulators appears to be reasonable as a countermeasure against snow induced flashovers.

Lidar fluorescence measurements of algal growth on electrical insulators

Fluorescence measurements using lidar techniques have been shown to be useful for monitoring of algal growth on e.g. historical monuments. In this experiment similar measurements were performed on electrical insulators to examine the correlation between algal growth and the quality of the insulator, a factor of importance in the high-voltage grid management.