Simultaneous Analysis of Benzotriazole, Tolutriazole Derivatives and Furanic Compounds: Passivators in Insulating Oil

Introduction

In transformers and condensers, insulating oil and paper are used to insulate conductors and cool the interior of electrical devices. These insulators are degraded by longterm operation or exposure to heat, which can lead to device failure. Accordingly, these insulators should be inspected periodically for to monitor the degradation of the device. Although insulating paper fixed to the device is difficult to remove, the insulating oil easy to collect is analyzed to verify device status. As one of the test methods, the amounts of additive compounds need to be quantified. Benzotriazole (1, 2, 3- benzotriazole: hereinafter called BTA) and tolutriazole derivative (N-bis[2-ethylhexyl]-aminomethyltolutriazol: hereinafter called TTAA) are added as passivators (metal deactivator) to insulating oil. Determination of BTA and TTAA is required because whether these passivators are added in insulating oil affect the risk of a degradation, such as sulfidation corrosion. The British Standards (BS148:2009) specify test methods of these passivators using the HPLC method. The ingredient of insulating paper used as a coating for windings in tranformers and condensers is cellulose. Cellulose is decomposed at high temperatures due to device operation and by the water or oxygen contained in degraded insulating oil. Decomposed cellulose is dissolved as furanic compounds in the insulating oil. Thus, the concentrations of furanic compounds in insulating oil are used as indicators of degradation of electrical equipment. This analysis using the HPLC method is specified by the ASTM D5837-15 standards. On the basis of the methods specified by ASTM and BS, we optimized the test method for passivators and furanic compounds so that these compounds could be analyzed simultaneously. This article introduces simultaneous analysis of BTA, TTAA and furanic compounds in insulating oil using an integrated HPLC system “ProminenceTM-i”.

November 18, 2020 GMT