Study On Influence Factors And Disposal Strategies Of Damp Inside Transformer During Inflatable Storage

Power transformer is one of the key electrical equipment in power grid for power transmission and distribution.The safety level of transformer plays an important role in the operation of power plants and substations.At present,the research on transformer is mainly focused on the transformer in operation,but few on the evaluation of dampness of transformer in the process of transportation and storage from factory to operation.A lot of operation experience showed that oil-paper insulation of transformer might have been damped before operation.However,there was no effective means of detection and evaluation at the operation site,resulting in a safety accident shortly after the transformer was put into operation.Large transformers are usually transported and stored by filling and drying nitrogen or dry air.However,due to the factors such as sealing and sudden changes of temperature,the oil-paper insulation of the transformer may be damped.In this paper,the technical route combining experiment and simulation was used to study the influence factors of internal dampness in the transformer during storage,the countermeasures under different dampness conditions and the drying strategy after damp.The main research work is as follows:(1)A damp test platform for transformer filled with dry gas with controllable internal pressure and leakage was built.The experimental study on the variation of internal moisture of transformer test model with external temperature,humidity and internal pressure was carried out.The results showed that as long as the micro-positive pressure in the transformer model was guaranteed under constant temperature conditions,the moisture in the atmosphere couldn’t enter the transformer model.Once internal pressure loss occurred,the moisture in the atmosphere would enter the experimental model due to the effect of temperature drop and moisture concentration difference.When the temperature changed drastically,external moisture might enter the experimental model.(2)A simulation model of the experimental model and the real transformer was established by Fluent.The effectiveness of simulation modeling and analysis methods was verified by comparing the experimental and simulation results of external moisture entering the test model under different temperatures and pressures.The influence of environmental temperature difference,equivalent leakage radius and other factors on internal moisture of real transformer was studied.The fitting formula of the variation of internal moisture mass increment?m with external water mass fraction w,day and night temperature difference?T,equivalent leakage radius r and other factors under the condition of loss of pressure was obtained,which was?m=w(1.9007?T+0.0527)r~2.(3)A real-time automatic detection and control device for temperature,humidity,pressure of transformer and ambient temperature and humidity was developed.An automatic air-filling control scheme with the functions of automatic switching between two cylinders and pressure release was proposed.It could effectively solve the problem of moisture inside the transformer caused by the internal pressure loss of the transformer and the sudden drop of the ambient temperature.Considering the drying equipment and process of transformer,a preferred method of transformer drying scheme based on index importance and multi-program comparison method was proposed.