The Calculation Of Pressure Rise In Switch Cabinet Due To Internal Arcing And Its Countermeasures

Internal arc fault is a serious catastrophic failure in switch cabinet,and it would cause great pressure rise in a short period of time,which is a significant threat to equipment and personal safety.It is of great importance to calculate the pressure rise in switch cabinet due to arcing fault and study the restraining measures.Aiming at the problem of the arcing pressure rise of the switchgear,the short-circuit arcing test and simulation are carried out in small enclosed containers,the simulation and the restraining measures of the real switchgear model are studied in this paper.Firstly,the short-circuit arc test is carried out in a small enclosed container.The law of pressure rise during the short circuit arcing in the closed container is studied.At the same time,based on the CFD indirect coupling analysis method,the distribution of the short circuit arcing pressure in the small enclosed container was simulated by ANSYS CFX.In addition,the influence of parameters such as grid quantity,grid type,simulation time step,arc size,arc energy and arc position on the calculation of short-circuit arcing pressure in closed container are analyzed.The results show that the grid size,grid type,arc size and arc position have little effect on the calculation.The simulation time step has some influence on the calculation result,and its selection should concider the calculation efficiency and calculation precision.Combined with the physical model of the actual switchgear,take the incoming room as the object of analysis.Combining the short circuit characteristics of the actual switchgear and the simulation results of the small model are obtained.The results show that the pressure wave in the compartment shows obvious shock wave characteristics at the initial stage of the arcing.The results show that the pressure wave in the compartment has obvious shock wave characteristics.When the short circuit current is 40 kA,the overpressure value of 30 ms is 689.47 kPa,and the impact force in the door is up to 401.68 kNAt the end of this paper,the influence of the design of the three pressure relief capsules on the pressure rise and fall of the compartment is analyzed,including the opening of the pressure relief cover and the influence of the negative pressure chamber on the short circuit arc pressure in the compartment.The longer the pressure relief is,the faster the pressure drop of the door should be;the maximum pressure of the door can withstand the maximum pressure analysis,the pressure of opening 1,2,3 pressure relief doors will not exceed its critical value,and Can allow a certain time to open the delay,which opened a maximum allowable opening delay is 7 ms,open 2 and 3 to allow the maximum opening delay of 10 ms.In addition,the negative pressure chamber on the compartment pressure rise has a certain inhibitory effect,compared with the open pressure gland,negative pressure chamber on the compartment short circuit arc pressure rise of the suppression effect is better.