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Physical Conditions of Electrical Equipment
Published in Bella H. Chudnovsky, Transmission, Distribution, and Renewable Energy Generation Power Equipment, 2017
For oil-filled transformers, the insulation system consists of oil and cellulose (paper). Under normal operating conditions, transformer insulation deteriorates and generates certain combustible and noncombustible gases. These gases are H2, CH4, C2H2, C2H4, C2H6, CO, and CO2. The main cause of gas formation in the transformer is the heating of the paper and oil insulation due to electrical problems such as corona (low-energy phenomenon) and electric arc (high-energy phenomenon) inside the transformer. The detection, analysis, and identification of these gases can be very helpful in determining the condition of the transformer. Dissolved gas analysis (DGA) is very helpful in the electrical industry for the detection of gases in oil.
Physical Conditions of Electrical Equipment
Published in Bella H. Chudnovsky, Electrical Power Transmission and Distribution, 2017
Dissolved gas analysis (DGA) is used to determine the concentrations of gases dissolved in the oil such as nitrogen, oxygen, carbon monoxide, carbon dioxide, hydrogen, methane, ethane, ethylene, and acetylene, according to ASTM D3612 [23]. The concentrations and relative ratios of these gases can be used to diagnose certain operational problems with the transformer, which may or may not be associated with a change in a physical or chemical property of the insulating oil. For example, high levels of carbon monoxide relative to the other gases may indicate thermal breakdown of cellulose paper, while high hydrogen, in conjunction with methane, may indicate a corona discharge within the transformer.
RCAM Case Reliability and Maintenance Component Modeling
Published in Lina Bertling Tjernberg, Infrastructure Asset Management with Power System Applications, 2018
According to the maintenance instruction [204], most regular maintenance performed on transformers is inspections, tests, and cleaning. A common test is dissolved gas analysis (DGA) of the insulation oil. If there are any leakages, gaskets are tightened, if there is rust on the tank it is treated and painted and the silica gel in the dehydrating breather is changed if it is needed. Further maintenance tasks are performed if tests and inspections show that it is needed. Even if the control equipment is alarming for a failure in the transformer, the performed maintenance is based on inspections and tests [205].
Stratifying transformer defects through modelling and simulation of thermal decomposition of insulating mineral oil
Published in Automatika, 2023
A. Manjula, Sangeetha S, Mustafa Musa Jaber, Hamad Mohamad A.A, Santosh Kumar Sahu, Rajesh Verma, Prashant Vats
Insulating mineral oil (IMO) is a petroleum derivative widely used in high voltage power transformers, especially in power transmission system devices. Due to the relevance of power transformers to the electrical system and the risks and high costs involved in their malfunction, predictive maintenance techniques have been developed and improved over the last 80 years [1–5]. These techniques aim to detect defects in power transformers. The best known of these predictive maintenance techniques is dissolved gas analysis (DGA). The DGA technique consists of collecting IMO samples from equipment in operation and quantifying the concentrations of some specific light compounds (gases) that are produced by the cracking of IMO molecules and remain dissolved in the liquid phase. The set formed by the concentrations of these light compounds is then used to verify the existence of a defect and, also, to classify this defect through semi-empirical algorithms, known as diagnostic methods. This correlation between concentrations of dissolved gases in IMO and types of defects in transformers is possible, since the energy dissipated to the oil in the vicinity of a defective region implies a local temperature and, therefore, determines which products will be predominant in the equilibrium of the reaction of consequent cracking [6]. The sensitivity of dissolved gas analysis makes it possible to identify defects that are still incipient, difficult to detect using other predictive techniques.
An Intelligent Genetic Fuzzy Classifier for Transformer Faults
Published in IETE Journal of Research, 2022
Amit Kukker, Rajneesh Sharma, Hasmat Malik
Power transformers play an important and critical role in ensuring uninterrupted power supply to installation. Several types of faults can render a transformer unusable or severely underrated. Such faults need to be monitored to ensure the reliability of power supply. Whenever a fault occurs in a transformer, gases such as CO2, CH4 and C2H6 are generated. Some of these gases, barring CO2, N2 and O2, get absorbed in the transformer oil. The concentration of these gases in the dielectric oil can be measured as parts per million or ppm [1,2]. This concentration of fault gases in oil is utilized in the dissolved gas analysis (DGA) technique for fault diagnosis. Conventional DGA techniques are International Electrotechnical Commission (IEC) ratio [3], key gas [3], Roger ratio [3] and Duval triangle [3].
Fault diagnosis of transformer based on fuzzy clustering and the optimized wavelet neural network
Published in Systems Science & Control Engineering, 2018
Wenhui Teng, Shuxian Fan, Zheng Gong, Wen Jiang, Maofa Gong
Dissolved gas analysis (DGA) technology is one of the most convenient and effective methods for fault diagnosis of oil-immersed transformers. It can diagnose the latent fault which may cause serious damage accurately and reliably. In recent years, various criteria for transformer fault diagnosis have been proposed at home and abroad using the DGA gas ratio as a characteristic parameter, such as the IEC ratio (Yang, Liu, Li, & Hu, 2007) and the improved Rogers ratio (Rogers, 1978). However, most of the fault diagnosis criteria are based on field experience, and there is misdiagnosis occuring in practical applications.