Transformer internal common fault types and treatment methods

Transformer internal fault can generally be divided into two categories: that is, overheating fault and discharge fault, overheating fault according to temperature level, can be divided into low temperature overheating, medium temperature overheating and high temperature overheating three kinds of situations; discharge fault can be based on the different energy density, can Divided into high energy discharge, low energy discharge and partial discharge three types. As for mechanical failures and internal flooding, it will eventually develop into an electrical failure.

The overheating fault is due to the accelerated deterioration of insulation due to thermal stress. If the thermal stress only causes the decomposition of the insulating oil outside the heat source, the specific gases produced are mainly methane and ethylene, and the sum of the two generally accounts for more than 80% of the total hydrocarbons, and the proportion of ethylene increases with the temperature at the fault point. Will increase, severe overheating will produce trace amounts of acetylene. When overheating involves a solid insulating material, in addition to the above-mentioned substances, a large amount of carbon monoxide and carbon dioxide are also produced, and if there is no CO or CO2, it may be a local metal overheating fault.

Discharge failure is the insulation degradation caused by high electrical stress. High-energy discharge failure, also known as arc discharge failure, this type of fault gas production, gas production is fierce, the use of methods to determine the dissolved gas in oil is not easy to pre-diagnose it, often after a failure, we can according to the oil The analysis of gas and gas components diagnoses the nature and severity of transformer faults. High-energy discharge fault gases are mainly acetylene and hydrogen, followed by ethylene and methane; if solid insulation is involved, the CO content is also high; low-energy discharge faults are generally spark discharges, and the fault gases are mainly ethylene and hydrogen. Due to its small fault energy, total hydrocarbons are generally not high; partial discharge fault gas production features the most hydrogen components (accounting for more than 85% of the total amount of hydrogen hydrocarbons), followed by methane, and the consequence of partial discharge is insulation aging. Its development will cause insulation damage and even cause accidents.

Transformer internal fault diagnosis method

1. Determine the gas content of the fault (analytical data) and compare it with the observed value of the dissolved gas content in the oil. If the gas concentration reaches the attention (total hydrocarbons, hydrogen attention values ​​are 150ppm, acetylene attention is 5ppm), attention should be paid to strengthen the follow-up analysis to identify the reasons.

2. Although the attention value has a certain reference in reflecting the probability of failure, due to the influence of related factors such as gas content in the oil, transformer capacity, operating mode, and operating time, it is difficult to correct only based on the analysis result of attention value. Diagnosing the severity of transformer faults must not be used as the sole criterion for dividing faults in equipment. On this basis, the effects of gas production rate and other aspects should also be fully considered, and the transformers to be diagnosed and the characteristic gases checked should be given some emphasis and differences. Only in this way can we further determine whether the transformer is faulty based on the analysis and make a preliminary estimate of the nature of the fault. The gas production rate is directly related to the size of the fault energy, the location of the fault, and the temperature of the fault point. By measuring the gas production rate of the fault gas, a further diagnosis can be made on the internal conditions of the transformer.

3. In order to understand the true cause of gas generation and avoid misjudgments caused by non-failure causes, we should also fully understand the structure, manufacturing, installation, operation, maintenance, and auxiliary equipment of the transformer under diagnosis during transformer fault diagnosis. Many aspects of the situation, combined with chromatographic analysis of data for comprehensive analysis, in order to correctly diagnose the transformer fault.