Research On On-line Monitoring Technology For Defects Of Oil Medium Seal Transformer

High-voltage transformer is one of the important electrical equipment in the substation,and oil-sealed power transformer is widely used as voltage and current measuring equipment in the substation with voltage level of 66 k V and above.In recent years,power grid accidents caused by the untimely discovery of internal defects of oil-immersed transformers have occurred at the substation site,which has brought huge economic losses to the power grid and threatened the life safety of power maintenance personnel.The traditional detection method of oil-immersed power transformer usually monitors a parameter of the transformer,and cannot monitor the internal defects of the transformer in operation in real time.Therefore,it is very necessary to study the online monitoring technology of oil-immersed power transformer and find the internal faults of the transformer in time to ensure the stable operation of the power grid.In view of the singleness of the monitoring object of the traditional monitoring method of oil-immersed transformer,this thesis proposes an online monitoring scheme based on temperature and pressure sensor.Through the simulation analysis of the temperature field under different defect degrees of the transformer and the calculation of the relationship between pressure and temperature,the online monitoring scheme and the measuring range of the sensor are determined,which solves the problem that a parameter cannot accurately judge the internal situation of the transformer.By recording the real-time changes of temperature and pressure,the false alarm and false judgment caused by external factors are avoided.At the same time,the installation position of the temperature and pressure sensors is selected at the top of the transformer expander.Compared with the external monitoring of the equipment,the monitoring data is less affected by the outside,and the pressure probe directly contacts the transformer oil,which solves the problem that the existing scheme is not sensitive to the pressure change,and the pressure measurement is not affected by the oil weight and oil pressure,improving the accuracy of pressure measurement.This thesis proposes a temperature and pressure sensor compensation algorithm to address the issue of error deviation during the use of temperature sensors and pressure sensors.By testing the measurement values of different temperature sensors at selected temperature values,the zero deviation error between temperature sensors is calculated.By compensating for the zero deviation value,the error is reduced.At the same time,the pressure sensor may experience deviation due to temperature changes,Therefore,a segmented interpolation algorithm was proposed to reduce the impact of offset on measurement,which greatly improves the measurement accuracy of online monitoring systems.The online monitoring software terminal based on Lora wireless transmission technology designed in this thesis forms the measurement system of the power Internet of Things.The designed multi-sensor fusion structure provides a transmission node for other sensors with the same transmission mechanism,provides a platform for future data fusion,and can real-time upload the internal parameters of the measured oil seal transformer to edge computing or background terminals,It can timely find the early defects in the oil medium sealed transformer in the substation.Through the above research,a complete monitoring system that can realize online monitoring and equipment data acquisition of the operating state of oil-immersed power transformer has been developed.It can obtain high-precision parameters of the internal state of oil-immersed power transformer and the operating state of the transformer in real time,which provides guarantee for the reliable operation of oil-sealed transformer and greatly improves the operating stability of the power system.