Current And Magnetic Flux Characteristics Of Interturn Short Circuit In Single Phase Transformers

As the core equipment for electrical energy transmission,It is very important for transformer normal operation to ensure the stability and reliability of the power system.Inter-tum short circuits in power transformer windings can cause problems such as current surges and magnetic flux saturation.Its continuous operation will cause the winding coil to bum out,causing greater accidents and affecting the safety and stability of power system seriously.According to statistics,winding inter-tum short circuit accounts for about 50%-60% of transformer winding faults.Therefore,Therefore,it is very important to study the inter-tum short circuit fault between transformer turns to maintain the stability of transformer operation.This article relies onthe National Natural Science Foundation of China(51507027),Jilin Science andTechnology Innovation Development Plan Project(20166014),and Jilin Science andTechnology Innovation Development Plan Project(20190303007SF)to study the current and magnetic flux characteristics of single phase transformers when inter-tum short circuits occur.Aiming at the problems of current mutation and excitation saturation caused by inter-tum short circuits in windings of single phase transformers,the operation coupling principle and short circuit current characteristics of the transformer after inter-tum short circuits have been studied.Based on the principle of transformer inter-tum short circuit operation,a transformer inter-tumshort circuit magnetic field calculation model was constmcted.The finite element method was used to calculate the winding inductance in magnetic field model,and the short circuit current was calculated based on inter-tum short circuit model.The magnetic field calculation model and the inter-tum short circuit model were iterated to realize the circuit-magnetic field coupling.The circuit-magnetic field calculation model was used to calculate the actual operating conditions of transformer inter-tum short circuit,and winding current under different inter-tum short circuit ratios and load levels was obtained,and the current change characteristics are summarized.Construct the mathematical relationship of inter-tum short circuit current with the change of short-circuit ratio and load rate,and analyze the change law of current.A single phase transformer inter-tum short circuit experimental platform was built,and short circuit current data was measured and compared with simulation calculation results.The results verified the correctness of circuit-magnetic field calculation model and principle of inter-tum short circuit.On the basis of summing up the current change characteristics,the flux change law of thefault is calculated to characterize the excitation characteristics.The main fluxes and leakage fluxes of primary and secondary windings under different short-circuit conditions are simulated and calculated.The short-circuit conditions include different short-circuit positions,different short-circuit ratios and different loads.Summarize its changing law.The results show that under the short-circuit condition of the transformer,the iron core near the short-circuit turn is saturated with excitation,and the leakage flux increases sharply.