Most substation transformer failures, excluding acts of man or nature, can often be traced to poor maintenance of the transformer or its related components. Catastrophic substation transformer failure can be prevented by thoroughly testing oil conditions on an annual basis and adopting a monthly visual inspection program. Most checks on a substation transformer are relatively simple: checking for oil leaks, oil level, temperature, on-load tap-changer operation, etc. However, if the transformer's oil paper insulation system is faulty, it can only be detected by oil analysis. By testing the physical and chemical properties of transformer oil, a number of problematic conditions can be identified before they lead to transformer failure. The reason transformer oil care and filtering is such an important part of substation transformer maintenance is because of the composition of most transformers. insulation systems. Oil and cellulose paper insulation systems are organic compounds containing hydrogen and the gradual oxidation of these compounds allows the formation of moisture. The byproducts of the process produce increased moisture levels and create an environment that overheats the transformer and further degrades the paper insulation, which in turn produces more byproducts. This cycle continues until the transformer fails. The two main contaminants that cause paper insulation and oil degradation are the presence of oxygen and/or water in the oil. Oil transformer oil is organic and therefore oxidizes and decays; creating oxidation byproducts that destroy the paper's insulation. Transformer oil aging is caused by the oxidation process of the oil; therefore, c...... half of the paper ......leads to transformer failure. Most units pass the oil through multiple paper cartridges during this process, and the oil passes through a 0.5 micron particulate filter as the last stage before entering the transformer. The main advantage of using a HORP unit is that the transformer can be serviced while it is being transformed. is still energized, saving the company the trouble and expense of de-energizing and doing without a valuable transformer that could generate revenue. Conclusion Substation transformers are key equipment that depend on the quality of their oil to provide consistent service, as a substation technician, taking care of the oil will be one of your duties. This lesson does not attempt to detail all the tests that can be performed on a substation transformer, but it should give you an idea of ​​what is involved in oil care and filtering.