Purpose – This paper aims to determine the effect of exposure of underground electrical cables to chemically contaminated water. Design/methodology/approach – Visual inspection and photography were carried out to record the appearance of electrical cables. Failed and un-failed cable samples were collected and analyzed using light microscopy, scanning electron microscopy coupled with energy-dispersive X-ray spectroscopy and Fourier transform infrared spectroscopy. Sand and water samples were chemically tested for contaminants. Findings – Underground low-voltage 0.6/1-kV cross-linked polyethene insulated cables belonging to a chemical production plant suffered failure after four years of service. Excavation of the cable trench revealed that the cables were buried in sand polluted with chemically contaminated water. The cables were discolored and covered with corrosion deposits. Experimental results indicated that the cable insulation was heavily degraded and the outer jacket of polyvinyl chloride exhibited cracks that had penetrated through its thickness. Water and sand surrounding the cable were found to have high concentrations of ammonia. Mechanical testing of the cables indicated high values of stiffness that could contribute to the formation of cracks at the surface. Practical implications – It was concluded that contamination in the water had degraded the cable, resulting in the development of a network of branched cracks within the cable insulation through which water could permeate, leading to eventual failure of the cable. Accelerated degradation took place due to exposure to the contaminated environment, which promoted aging and brittleness. Continued exposure of electric cables to contamination would lead to power failures and plant shutdowns. Originality/value – This paper provides an account of a failure investigation of low-voltage electrical cable buried underground. It discusses the role of contaminated environment in the eventual failure of electrical cable due to corrosion. This information will be useful for plant engineers and project managers working in any industry that makes use of chemicals.
This paper investigates the technical performance of 230 kV field-aged composite insulators in the coastal region of Saudi Arabia. Two insulator samples removed from the 230 kV line after 20 years of service are assessed at KFUPM High Voltage Lab (KHVL). Different assessment techniques, such as visual inspection, contact angle, surface pollution severity, electrical withstand, and material characterization are utilized to evaluate the insulator performance. Equivalent salt deposit density (ESDD) and non-soluble deposit density (NSDD) techniques are used for the surface pollution severity measurements. Clear views of surface changes and surface hydrophobicity conditions are displayed. Scanning electron microscope (SEM), energy dispersive x-ray spectrometry (EDX), and Fourier-transform infrared spectroscopy (FTIR-IR) techniques are utilized for the material characterization. The visual inspection reveals small and big cracks in the insulator sheds. Hard breakable portion areas, many shed cuts, changed color areas, and whitish parts are visually noticed in the insulator surface. Such changes confirm the aging condition effect of the insulator units. Furthermore, the samples are subjected to laboratory clean fog tests to check the electrical performance of the samples. Informative results are given for the current condition and performance for the 20-years, fieldaged insulators. Additionally, the experimental results are presented for the rest of the insulator life period. Utilization of the existing line insulators has been evaluated. Finally, discussions and recommendations for the future handling of the insulators at the 230 kV line are highlighted.
Three long-rod silicone rubber composite insulators used in 230 kV power transmission lines were evaluated for aging affects. The insulators were obtained from various outdoor desert locations within Saudi Arabia where they had been in service for 6 years. Surface degradation associated with the aging process was analyzed by using Scanning Electron Microscopy (SEM) coupled with Energy Dispersive X-ray Spectroscopy (EDS), Fourier Transform Infra-Red Spectroscopy (FTIR), and Electron Spectroscopy for Chemical Analysis (ESCA). Electrical performance of insulators was evaluated by Rapid Flashover Voltage Tests (RFVT) and Pollution Severity Measurement Tests. Depending on their locations of service, the samples exhibited various types of pollutants at their surfaces. The analysis indicated that the insulator material showed localized surface degradation while there was no evidence of micro-cracking. Furthermore, it was noted that the electrical performance of the insulators was not significantly affected by exposure during the in-service period.
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