Study On Moisture Content Evaluation Method Of Transformer Oil-Paper Insulation Based On FDS

Because moisture can accelerate the aging of oil-paper insulation materials,it has a serious impact on the insulation status and electrical life of the insulation system in oil-impregnated power Transformers.Therefore,it is of great significance to accurately evaluate the moisture content in oil-paper insulation of Transformers and power systems.At present,the research on the evaluation of moisture content of oil-paper insulation at home and abroad mainly focuses on the influence of water content,temperature,insulation structure and other factors on the response characteristics of oil-paper insulation medium under laboratory conditions,and the search for dielectric response characteristics to indicate moisture content of oil-impregnated paperboard in oil-paper insulation.And there is very little quantitative analysis on the relationship between transformer oil-paper insulation moisture content and frequency domain dielectric spectrum curve.It is necessary to carry out research in this area.In order to evaluate the moisture content of a transformer’s insulation pressboard by the dielectric response insulation technique,the frequency domain dielectric theory,transfoemer XY-equivalent model and calculation model of dielectric constant of composite media were theoretically derived firstly in this paper,and the relationship between moisture content in insulating pressboard and dielectric loss factor of XY equivalent model was obtained,and a quantitative calculation model of frequency domain dielectric spectrum of damp transformer oil paper insulation was established.In addition,combining the experimental test data with the basic idea of “frequency-temperature superposition”,the specific expressions of the real and imaginary parts of the complex dielectric constant of dry oil-impregnated cardboard were obtained.Based on the quantitative calculation model of the frequency domain dielectric spectrum of the damp transformer XY equivalent model,an iterative fitting algorithm for evaluating the moisture content of oil-paper insulation was designed.In terms of experiment,the XY equivalent models with different moisture content were prepared in laboratory firstly in this paper,and the moisture content and the frequency domain dielectric spectroscopy of the above samples were tested respectively by Karl Fisher titration method and IDAX-300.Then the two samples were validated in the quantitative calculation model of frequency domain dielectric spectrum of damp transformer oil paper insulation and the iterative fitting algorithm under both normal temperature and variable temperature conditions.Finally,the accuracy of the oil-paper insulation moisture iterative fitting algorithm was verified by the frequency domain dielectric spectrum test results of an actual transformer.