Indian Journal of Science and Technology

Abstract

Objectives: Analysis of dissolved gas in transformer oil is very important because the fluctuations in the oil will change the process of content of dissolved gases which will show effect on many factors such as oil temperature and external environment. Hence, it is important to propose a preprocessing technique through Duval’s triangle which is important step in the machine learning process for predictive maintenance of transformer. Methods: The dissolved gas content for 500 kVA transformer oil based on the training and testing data for fault free condition taken for the period of 5 years (2013-17) and faulty condition taken for 3 years (2018-2021), has been evaluated using Duval’s triangle method to express gas concentrations of CH4, C2H2 and C2 H4 in ppm as percentages of their total. High pass filter, scaling and windowing techniques are used for preprocessing the giant DGA data. Findings: The results show that unusual and undesirable intensity in the CH4, C2H2 and C2 H4 gasses is eliminated by using proposed high pass filter technique. More visible output signal by the way of reducing its dimensionality is obtained by applying proposed scaling and windowing techniques for the filtered DGA data. Novelty: Most of the researchers have used limited samples of DGA data for condition monitoring due to which diagnosis of transformer faults is not accurate. To accurately diagnose transformer faults, large set of training and testing data is required. In this paper, the pre-processing of giant DGA data consisting of 960 samples of fault free training with data size of 480000 x 55 and 500 samples of fault free testing with data size of 250000 x 55, faulty training and faulty testing with data size of 960000 x 55 is presented. The preprocessing method adopted will be used in real time application to provide suitable data to train the advanced deep neural network like LSTM through MATLAB interfacingwith graphical processor unit. This is required for condition monitoring and accurately predicting the faults in above mentioned transformer.

Keywords: Dissolved Gas Analysis; Duval’s Triangle method; Predictive maintenance; Data Ensemble; Pre-processing; Scaling; Windowing