Insulation Condition Assessment Through Spectroscopic and Chemometrics Analysis

The condition of high voltage cable, power transformer and generator insulation is affected by a number of manufacturing and operating variables. Although forensic examinations of solid insulation failures are commonly conducted and there are many electrical tests to assess the condition of the insulation system, there has been only a limited effort to investigate and spatially map the changes in chemical characteristics and properties that can also affect failure. We have applied a range of non-destructive spectroscopic methods such as infrared, Raman, including their respective microprobe methods, and UV-VIS-NIR spectroscopy to measure spatially resolved chemical composition and structure of polymeric insulated cables, power transformers and generator stator insulation both before and after electrical and thermal stressing. By applying multivariate statistical analysis (MVSA), we have been able to explore and extract relationships between chemical change in the material and "intrinsic variables" such as stressing time, temperature and voltage as well as explore the relationships with physical properties and performance such as electrical breakdown strength, mechanical strength and charge mobility. Recent work illustrates the power of such methods in exploring key property and performance relationships and the ability to map these spatially with new remote and rapid spectroscopic optical probe methods. We propose that well-populated MVSA models can relate chemical and physical change in solid insulation systems to electrical measurements, to potential indicators of insulation ageing and provide a predictive capability for insulation condition assessment which could assist in insulation life prediction.