Quality assessment of Paper Insulated Lead Covered cables using Near-Infrared Spectroscopy

Abstract

The increasing expansion of the electrical network accentuates the need for a better understanding of the quality of the existing infrastructure. Assessing the quality of the individual cables becomes instrumental in prioritizing replacements and grid reinforcements within the network. A critical evaluation of insulation quality in paper insulated lead covered cables is important to ensure a robust electricity grid. Moisture plays a key role in the degradation of the paper insulation. In this thesis a novel microcontroller based near-infrared spectroscopy system design is proposed which is able to measure the moisture content of paper insulated lead covered cable insulation with a theoretical accuracy of about ±1% moisture content, while being cost effective and portable. It achieves this accuracy by making use of an outlier detection algorithm which is able to increase the accuracy of the system from ±3% to ±1%, by removing outliers of individual sensors and averaging the results of multiple measurements. The resulting output of the algorithm is linked to the asset number of the paper insulated lead covered cable under test, and uploaded to the cloud to enable further data analysis. The proposed near-infrared spectroscopy system performs measurements on one particular absorption band of water; the absorption band around 1450 nm. Due to the influences of stray light, a design of a paper insulation sample holder is proposed. This sample holder is customized to the used components in the design and fixes the samples in place, which limits measurement inconsistencies. A testing procedure is proposed to link the sensor output to the moisture content of the paper insulation sample. A linear relation is found between the sensor output and the moisture content of the paper insulation samples at a moisture content of 0% to 20%.