Oil Immersed Transformers Fault Analysis
Insulation degradation: In the past 10 years, insulation degradation was the second leading cause of failures. Due to the deterioration of insulation, the average life of oil-immersed transformers is 17.8 years, which is far below the predicted life of 35-40 years. The average life of an oil-immersed transformer in 1983 when it failed was 20 years.
Line inflow: Among all the factors that cause oil-immersed transformer failure, line inflow (or line disturbance) is the most important. This type includes power distribution (TD) anomalies such as misoperation, pairing of oil-immersed transformers, lead arcs of splitter switches, etc., driving overvoltages, peak voltages, line faults/flash lights, etc. There are wrong pairs.
Bad Process/Manufacturing: In study, only a fraction of failures were caused by process or manufacturing defects. For example, there are loose sockets and the presence or absence of support, loose cushions, poor welding, poor core insulation, insufficient short-circuit strength, foreign objects in the tank, etc.
Insufficient maintenance: Insufficient maintenance is considered the fourth cause of failure of oil-filled transformers. This species contains illegal protection devices, devices without oil immersed transformers, leakage of coolant, dirt, corrosion.
Overload: This type of fault includes faults identified as overloads and refers only to oil immersed transformers in small horse-drawn carriages that operate beyond the nameplate power for extended periods of time. Overload often occurs when the load on power stations and power companies continues to increase slowly. Eventually, the oil-immersed transformer will cause premature aging of the insulation due to overload operation, and the temperature is too high. If the insulating board of the oil-immersed transformer deteriorates, the insulating strength of the insulating paper will decrease. For this reason, insulation breakdown occurs due to the influence of an external failure, which becomes the cause of the failure.
Lightning strikes: Based on changes in compositional classification, there appear to be fewer lightning strike waves than previous studies. Now, as long as it is not an obvious lightning accident, the general impact fault is classified as inrush current of the line.
Three-phase load imbalance: due to the three-phase load imbalance, long-term overload occurs, and the temperature is too high, resulting in insulation deterioration, resulting in short circuit between coils or short circuit between phases.
Connection Slack: Connection slack can also enter under-maintained areas, however, because sufficient data can be tabulated separately, unlike previous studies. This includes the manufacturing process and maintenance of electrical connections. One of the problems is that, although this phenomenon is decreasing in recent years, there is an inappropriate distribution of metals of different properties. Another problem is improper tightening between bolted connections.
