The purpose of transformer oil filter is to remove the water and impurities in the oil, improve the oil resistance to electricity, protect the paper insulation in oil, but also to a certain extent, improve the physical and chemical properties of oil.

配电电力变压器大都安装在露天环境中，绝缘油(变压器油)受外界杂质、和空气接触以及设备本身运行温度较高的影响，使油的质量逐渐变坏。变质后的绝缘油(变压器油)就不会起到应有的绝缘、冷却作用。为防止因油质变坏而致使的安全运行受到影响，应对正常运行的配电定期采油样进行化验分析，并根据分析结果对油进行相应的处理。配电运行油化学监督的检验周期规定为至少3年一次。常规检验项目包括酸值、水溶性酸、闪点、击穿电压、外状。

Most of the power distribution transformers are installed in the open environment, the insulation oil (transformer oil) is affected by the external impurities, air contact and the operating temperature of the equipment itself. After the deterioration of insulating oil (transformer oil) will not play the proper insulation, cooling effect. In order to prevent the oil due to deterioration caused by the safe operation of the affected, to deal with the normal operation of the distribution of oil samples for testing and analysis, according to the results of the oil for the corresponding treatment. The inspection cycle of chemical monitoring of distribution operation oil shall be defined as at least 3 years. Routine inspection items include acid value, water soluble acid, flash point, breakdown voltage, external.

应注意的是：若设备经常带负荷比较高，应在规定试验周期的基础上，增加检验次数;若经检验的项目某些指标明显接近所控制的极限值时，也应增加检验次数;由于运行油的质量随老化程度和所含杂质等条件的不同变化很大，通常不能单凭一种试验项目作为评价油质状态的依据。应根据所测定的几项主要特征指标进行综合分析。

It should be noted that: if the equipment often load is relatively high, should be based on the provisions of the test cycle, increasing the frequency of inspection; if some indexes inspection items significantly close to the limits of control value, should also increase the frequency of inspection; because of the quality of running oil with aging degree and different impurity conditions a large, usually can not be solely a test project as the evaluation basis of condition of oil. Comprehensive analysis should be carried out according to the main characteristics.