Numerical Simulation Of Instabilities In Pinch Effect Of Liquid Metal

At present,China is in the stage of power transformation.The concept of "carbon neutral" will accelerate the increase of the proportion of new energy in the energy structure.This new energy collection process is generally intermittent and random,which will lead to a certain degree of fault current when it is incorporated into the power system,At the same time,the improvement of the degree of interconnection in the power system will also increase the fault current in the power system.Compared with other solutions,using fault current limiter to suppress fault current is a fast and cost-effective solution,which can effectively alleviate the impact of fault current on power system.In this paper,a working principle of liquid metal current limiter,pinch effect,is taken as the research object.The whole process of pinch effect in liquid metal conductor is numerically simulated and the instability is analyzed.Based on the shallow water approximation,the mathematical model is given,the physical model is established with the assumption of gravity direction,and the Chebyshev collocation spectral method based on fast Fourier transform is used to simulate the quasi one-dimensional physical model and analyze the instability.Through the numerical simulation of the process of pinch effect,the characteristics of free surface wave and the change of corresponding temperature are explored.Compared with the simulation results without considering temperature,the effect of buoyancy on the pinch effect is explored.Through the analysis of the simulation results of different initial disturbance ratio coefficients and current density ratio,the influence of them on the occurrence of pinch effect is explored.Through the above research,we can better understand the principle of liquid metal fault current limiter and find problems,so as to carry out better design and manufacture.The results show that the change of the free surface of the liquid metal during the pinch effect has certain characteristics,which does not change with the initial disturbance ratio,and will seriously reduce the buoyancy effect.The buoyancy force will increase the fluctuation of the free surface and promote the occurrence of pinch effect.The change of temperature depends on the change of radius.The temperature does not change much in the process of pinch effect,but increases sharply at the last moment before the circuit breaking.The buoyancy force produced by temperature rise has limited influence on the whole process.By changing the critical current density and the initial radius length,the liquid metal current limiter can quickly resist the large fault current.