变压器在装置过程中油品或固体绝缘资料中存在着尘埃等杂质，运转一段时间后，胶体杂质慢慢析出。变压器胶体粒子直径很小（普通为 10-gin～10 m），扩散慢，但有一定的活动能量。粒子可自动聚结，由小变大，为粗分散系，处于非均衡的 不稳定状态，当超出胶体范围时，变压器因重力作用而堆积。油中存在溶胶后，沉淀物超越0.02%时，便可能惹起电导超越介质正常电导的几倍或几十倍，从而招致介损值增大。
There are dust and other impurities in oil or solid insulation data of transformer during the process of installation. After a period of operation, colloidal impurities gradually precipitate. The diameter of colloidal particles in transformer is very small (usually 10-gin~10 m), which diffuses slowly, but has certain active energy. Particles can coalesce automatically, from small to large, and become coarse dispersed system. It is in an unbalanced and unstable state. When it exceeds the colloid range, transformers accumulate due to gravity. When the precipitate exceeds 0.02% after the presence of sol in the oil, the conductivity may exceed several or several dozen times of the normal conductivity of the medium, thus causing the dielectric loss value to increase.
The transformer manufacturing structure is analyzed. At present, some transformer manufacturers think about eliminating oil purifier (thermal siphon) from the angle of reducing oil leakage of transformer, which has a certain influence on the increase of dielectric loss factor of transformer oil. If the transformer on the transformer is equipped with oil purifier, the quality of insulating oil will be stable. It can "absorb" the moisture in the insulation during the operation of the transformer and improve the electrical performance of the insulation, thus slowing down the increase of moisture in the insulation.
Transformer microbial bacterial infection is mainly caused by bacterial biological immersion during installation and overhaul. Transformers contain water, air, carbons, organic matter, minerals and trace elements in oil due to pollution, thus constituting the basic conditions for the growth, metabolism and reproduction of fungi. Because microorganisms contain abundant proteins and have colloidal properties, the practice of microbial contamination of oil is a kind of microbial colloidal contamination. The colloids of microbial transformers are charged, which increases the conductivity of oil, so the conductivity loss increases. Transformer oil is in fully sealed, anoxic and matte body, microbial anaerobic and anaerobic in oil. When dielectric transformer loss test is stopped after a long time, especially when it is placed in colorless transparent glass bottle, its dielectric loss value will decrease. Transformers have different loads and operating oil temperatures in different periods, and microorganisms multiply at different temperatures. Oil temperature runs in the range of 50 ~70 ~C. The propagation speed is the fastest, so the dielectric loss increases relatively fast. Therefore, temperature has a great influence on the growth of microorganisms in oil and the performance of oil. The dielectric loss factor in winter is comparatively stable.