A method for recognising the type of fault in oil-filled equipment based on the gas percentage

Abstract

One of the main tasks of the electricity sector is to ensure a reliable supply of electricity. Transformers play a key role in this, as their operation determines the reliability of the energy infrastructure. One of the factors that is common to all countries and affects the reliability of equipment is the ageing of this equipment as a result of various processes, including faults developing inside this equipment. One of the most effective methods of diagnosing high-voltage oil-filled equipment is the dissolved gas analysis, which allows for the recognition of various types of faults. Using different diagnostic criteria (gas ratios, percentage of gases, and gas to gas ratios with maximum content), different types of faults can be identified. One of the most commonly used diagnostic criteria is the percentage of gases. However, the reliability of fault detection by different methods for the same data varies considerably. The greatest difficulty arises when recognising combined faults. Therefore, the issue of developing a method for recognising the type of fault based on the results of the analysis of gases dissolved in oil using the percentage of gases as a diagnostic criterion is relevant and of practical importance. The article proposes an analytical method for recognising the type of fault in high-voltage oil-filled equipment based on the percentage of five gases in the oil. The article considers the recognition of different types of faults, for which the gases with the maximum content are hydrogen, methane, ethane, ethylene and acetylene. The values of the percentage of gases characteristic of a particular type of fault are given in the form of tables, which show the ranges (minimum and maximum values) and average values of the percentage of gases. As a result of the analysis, for the first time, the ranges of percentage gas content values for 50 groups of faults of various types, including combined faults, were established. This makes it possible to significantly increase the number of faults that can be recognised using the percentage of gases as a diagnostic criterion. In the process of developing the method, it was found that in a number of cases, it is not enough to use only the percentage of gases, but there is an objective need to use both the values of gas ratios and fault nomograms to determine the type of fault.