Dual Taps on Transformer Bushings

Abstract

In power systems, High Voltage (HV) bushings play a major role in preventing major transformer failures or any unplanned outages in the network. It conducts current through a wall or a grounded steel tank of a transformer. According to the statistics, bushing failure is one of the major causes for the transformer failure, accounting for 15-30%. Therefore, it brings greater importance to monitor the condition of the bushing through an online monitoring system continuously. Also, the condition of the bushing is monitored periodically by manual testing after taking the bushing out of service. In Hitachi Energy Sweden AB, the bushings are provided with a single tap configuration, either a test tap or a voltage tap, to connect the online monitoring system or the offline equipment during manual testing. The customer needs to disconnect the online monitoring system to perform manual (offline) testing. The process of connecting and disconnecting the online measuring system is timeconsuming and poses safety issues to the testing personnel. The goal of this thesis work is to develop a dual tap configuration that allows the customer to perform offline and online measurements in parallel. To develop the intended dual tap configuration, the primary step was to analyze the feasibility of the possible configurations, followed by generating concepts that fulfill the desired functionality. Once the concepts were generated through functional analysis and morphological matrix, the next step was to screen the concepts through elimination matrix, Pugh matrix, and Kesselring matrix, resulting in finalizing the concept. Finally, the chosen concept was developed into a digital prototype that serves the intended functionality.