COLUMN of minimum reduction of oil dielectric strength – key oil quality parameters. We should never forget that apart from being an insulator and a coolant, oil is also an information carrier. Tat infor- mation could be related to a condition state of another critically important component - paper, afecting overall transformer performance and its insula- tion life span. Tere are some physical and chemical parameters that characterise oil quality. Among these are dielectric loss factor, thermal and electrical conductance, re- How water affects WUDQVIRUPHU RLO TXDOLW\ DQG helps monitor its aging While insulating liquid could be of differ- HQW W\SHV ˴ VXFK DV PLQHUDO RLO QDWXUDO DQG V\QWKHWLF HVWHUV WKH LPSDFW RI PRLVWXUH LV universal plain not only how moisture afects the quality of the insulating liquid, but also how online sensing of moisture param- eters can be used in continuous moni- toring of oil condition, rate of oil deteri- oration and aging of both oil and paper insulation. Various defnitions related to moisture in transformer used in this ar- ticle were introduced in previous issues of this magazine [1, 2, and 3] and the reader is advised to refer to these issues to recall some of the concepts and ex- amples. Te article also reveals a method of continuous online determination of absolute water content of insulating liquid and the means for determination A s it is well known, transform- er insulation consists of two major components – oil (liq- uid insulation) and cellulose based solid insulation (also colloquially known as “paper”). While insulating liq- uid could be of diferent types – such as mineral oil, natural and synthetic esters, the impact of moisture is universal. For that reason, we will be using the term “oil” throughout this article assuming that the fndings here hold true for all types of insulating liquids. Tis article, the forth in series of water in transformers column, attempts to ex- 76 TRANSFORMERS MAGAZINE | Volume 6, Issue 4 | 2019 brought to you by CORE View metadata, citation and similar papers at core.ac.uk