Research On The Moisture Migration Characteristics And Temperature Effect In Multi-surround Oil-paper Insulation

Moisture intrusion which may lead to insulation deterioration is one of the main reasons for the failures of transformer oil-paper insulation bushing.At present,the monitoring on bushing moisture defects is imperfect and the moisture characteristics of bushing are not clear.It is necessary to study the moistening process of bushing in order to assess the moistened status of bushing and detect moisture defects with electrical parameters.The condenser core which consists of the main insulation of bushing belongs to multi-surround oil-paper insulation.The moisture would spread and migrate in the oil-paper insulation gradually when a bushing was moistened.The direction and speed of moisture migration are closely related to temperature.It is necessary to study the moisture migration characteristics and temperature influence in the multi-surround oil-paper insulation structure.This study is of great theoretical significance and engineering value to the moistened status assessment and moisture defects monitoring of bushing.In this paper,the multi-surround oil-paper insulation model which was similar to the actual bushing condense core was designed.The model moistening property research platform was established for moisture defect simulation and temperature control.The moisture content in oil and paper after different standing time of the moistened model was measured and analyzed.The characterization called average water content was presented to describe the average moistened status of model.The characterization called dispersion degree was presented to describe the moisture distribution of model.The research indicated the characteristics of moisture migration in multi-surround oil-paper insulation at room temperature 20°C.The moisture content in oil increased rapidly in the early standing period,then gradually decreased in the medium and late standing period because of the migration into the paper;The moisture distribution of model paper has regional characteristics that the moisture content of the top area of model is dispersive,while the moisture content of the other four areas is evenly distributed,and the difference between regions is obvious;The moisture absorption speed of model paper has regional characteristics that the growth rate of moisture content between different regions is obviously different.The effect of temperature on the moisture migration characteristics of multi-surround oil-paper insulation includes was studied.The trend of moisture content in oil would change with temperature that the moisture content in oil would increase first and then fluctuate around an equilibrium value when the temperature raised;the temperature effect on the moisture distribution characteristic was little and the moisture value sequence of areas was not changed when temperature altered;the temperature had an obvious effect on overall moisture absorption rate and local moisture absorption rate of model.