Development of portable near infrared optical sensing prototype to determine inhibitor content in transformer insulating oil

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Raudhah Izyan Rohimi
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Power transformer is a main component in the transmission and distribution of electrical energy in a power network. The prevention on catastrophic breakdown of transformer for power utilities is significant to ensure that the power transformer is operating under optimal conditions. Hence, various preventive maintenances were carried out, including monitoring and inspection on the condition of the inhibitor content in transformer insulating oil. Transformer oil, which is also known as insulating oil, is an important component in power transformer which acts as a coolant and insulation. The presence of inhibitors in the insulating oil increases the lifespan of the oil with respect to oxidative degradation in the presence of oxygen. However, the current standard used to measure the inhibitor concentration in insulating oil, which is the Fourier transform infrared (FTIR) spectroscopy conforming to the IEC 60666 standard, involves a few techniques that require lab-based test with costly instrument utilizing mid-infrared wavelengths near 2739 nm. Based on previous researches, it was found that inhibitor content in transformer oil also exhibits an optical absorbance peak at near-infrared wavelengths at 1403 nm. Thus, this work comprehensively characterized the inhibitor content in transformer oil at near-infrared wavelengths. Then, a portable optical sensing prototype was designed and fully developed to work at near-infrared wavelengths of 1390-1420 nm. Internet of Things (IoTs) elements were also incorporated into this prototype, in which the user could carry out measurement either using the graphical user interface or using the Telegram application. The prototype was calibrated and validated by comparing the results with the inhibitor content concentration measured by the accredited laboratory using IEC 60666 standard, with an average percentage error of 0.02 %. In contrast to the conventional measurement method, this prototype provides a portable, cheaper, and quicker solution in measuring the inhibitor content concentration in transformer oil.
TK8360.O67 R38 2019
Optical detectors , Infrared imaging , Electric insulators and insulation