检测变压器油对水的界面张力不是用来表征油的流动性能的，反应的是油与水的亲合力，张力大则油水不易混容(乳化)，油在精制中易脱水(变压器油的一重要指标是微量水PPM不能超标)，油在运行中也不易吸水，故变压器油的标准中要规定其界面张力要大于一定的值。
The detection of the interfacial tension of transformer oil to water is not used to characterize the flow performance of oil, but reflects the affinity of oil and water. If the tension is large, the oil and water are not easy to mix (emulsify), the oil is easy to dehydrate in refining (an important index of transformer oil is that the ppm of trace water cannot exceed the standard), and the oil is not easy to absorb water in operation. Therefore, the standard of transformer oil should stipulate that its interfacial tension should be greater than a certain value 。
如果变压器油受到污染或在运行中氧化、老化而生成一些微量新物质，毫无疑问都会使油对水界面的张力下降，张力的下降在某些方面又客观反应了油中异物的多少，这些微量的异物可能很难定性定量的检测，但是会对油的介质损耗有较明显的反应，虽说油对水的界面张力与油的介质损耗两者不是简单的线性关系，但变压器油对水的界面张力，肯定会影响油与水混容的难易程度，油对水的界面张力小，油在脱气(脱水)精制过程就较难，所需时间较长，反之油也较易吸"潮"，而油中微量水的存在都会对油的很多性能有较大的影响。
If the transformer oil is polluted or oxidized or aged in operation, and some trace new substances are generated, there is no doubt that the interfacial tension between oil and water will decrease. The decrease of tension objectively reflects the amount of foreign matters in the oil in some aspects. These trace foreign matters may be difficult to be quantitatively detected, but they will have a more obvious reaction to the dielectric loss of oil, although the influence of oil on water is obvious The interfacial tension and the dielectric loss of oil are not simply linear, but the interfacial tension of transformer oil to water will definitely affect the difficulty of oil and water mixing. If the interfacial tension of oil to water is small, the degassing (dehydration) refining process of oil is more difficult and takes a long time. On the contrary, the oil is easier to absorb "moisture", and the existence of trace water in oil will have a great impact on many properties of oil Ring.
因此：变压器油对水的界面张力数值变小能客观的反映出油中不明微量杂质的存在，以及油水间相互亲疏力的大小。
Therefore: the value of interfacial tension between transformer oil and water becomes smaller, which can objectively reflect the existence of unknown trace impurities in oil, as well as the mutual affinity between oil and water.
