Research On Distribution Characteristics Of Oil Flow Velocity Field In Transformer With Internal Arc Discharge

Large-capacity transformers are expensive and have complex equipment structures.Once they fail,they can cause damage to the transformer body,affect the stability of power system operation,generate huge economic losses,and even cause personal safety accidents.Therefore,it is urgent to achieve online monitoring of transformer operation status.Arc discharge fault is the main defect of transformers,which can be detected timely and effectively to ensure the safe and stable operation of transformers to the maximum extent.However,at present,there is a lack of effective online monitoring methods for transformer arc discharge faults,and it is impossible to grasp the internal health status of the transformer in real time.When an arc discharge fault occurs,the energy and temperature generated by the discharge can lead to the decomposition of various gases from the oil,which in turn leads to the surge of the oil flow in the transformer,causing changes in the speed of the oil flow in the transformer,and directly changing the distribution of the oil flow field inside the transformer.Therefore,it is significant to study online detection methods for transformer arc discharge faults based on flow field characteristics.In this paper,the measurement methods and distribution characteristics of transformer oil flow field are studied,which provides a basis for online detection of transformer arc discharge faults based on flow field characteristics.In order to obtain the flow field distribution characteristics of the transformer,a three-winding transformer model is established in this paper.The flow field distribution under normal operation and arc discharge conditions is simulated and studied,and the influence of arc discharge on the flow field distribution is obtained.The results show that the distribution characteristics of the transformer flow field are different for arc discharge faults at different locations.Based on this,the optimal arrangement scheme of flow field sensors and the diagnostic basis for internal arc discharge faults are proposed.According to the results,the performance requirements of the sensor are given as follows:the measurement range should be 0.01-3m/s,and the resolution should be 0.01m/s.Based on the optical Doppler effect and the particle size in transformer oil,this paper determines the applicable light scattering theory,and analyzes the light scattering effect of oil particles according to this theory.At the same time,according to the principle of Doppler effect-measuring the velocity of fluid,that is,measuring the velocity of particles in the fluid,the following analysis of particles present in the oil is performed,and it is determined that there are particles in the oil that have a good following property that can be used for tracing.This not only analyzes the feasibility of measuring the oil flow rate,but also provides a theoretical basis for the development of subsequent sensors.Based on the basic structure and performance requirements of the sensor,the final structure of the optical flow velocity sensor was obtained,and the specifications of the main devices such as lasers and photodetectors were determined.On this basis,the sensor performance was analyzed.The results showed that the theoretical parameters of the sensor met the requirements.The development of the sensor was completed,and different experimental platforms were established.Based on the developed flow velocity sensor,flow velocity field measurement experiments were conducted,The feasibility of the sensor in practical measurement is verified.At the same time,an experiment of simulating arc discharge on a real 110kV transformer is conducted,and the experimental results match the simulation results.