12/24kV Switchgear Internal Arc Fault Analysis And Protection

The medium voltage switchgear is an anti-arc product.In order to verify the limit performance of the medium voltage switchgear,the internal combustion arc test of the switch cabinet is used to simulate the arc fault in the cabinet.The arc type test of switchgear is a compulsory test,and the test procedure is very short.Through the analysis of the type test,the weak link of the cabinet can be found,and the improvement of the actual product is provided with theoretical support and improvement direction.The main work of this paper is as follows:Firstly,the instantaneous three-phase voltage and current waveforms are acquired by phase to phase short-circuit test,and the discrete arc integral method is used to estimate the instantaneous arc energy value.The calculated arc energy values are compared with the measured values.The results show that the results of simpson integration are close to the measured values,and the error is less than 4%.Through the multiple 31.5kA 1s and 40 kA 1s internal combustion arc tests,the influence of cabinet width and arcing grade on the test was analyzed.Through the test analysis of maximum pressure time 12 kV switchgear in 15-20 ms,24kV switch cabinet appears maximum pressure time of about 20 ms.The least square method is used to fit the arc energy data obtained by the test.The fitting function has important guiding significance for the application in engineering field.The arc energy value of the switchgear can be obtained by fitting the function,and the strength of the switchgear is verified by the strength theory.Through the finite element software Ansys Workbench static linear mechanical simulation,the simulation results show that the circuit breaker chamber the maximum stress appears in the center of the baffle plate moving contact position and pressure relief plate center position,and the structural strength meets the design requirements.Through the arc energy curve to calculate the pressure inside the cabinet,the internal combustion of the switch cabinet for strength check and structural stress simulation analysis,combined with the previous test results to get the door is to withstand the relatively weak part of the pressure.In this paper,the optimum design of switchgear cabinet door is carried out from two aspects of mechanical strength and cabinet sealing.It is put forward that the built-in lock door has better pressure resistance and tightness.An internal combustion arc test is carried out for the optimized cabinet,and the test results show that the cabinet meets the arc requirement,which indicates that this paper is feasible for the calibration of cabinet strength and cabinet door optimization.Finally,by comparing the arc protection with overcurrent protection execution speed,the arc protection cut off the fault faster than the overcurrent protection,can quickly stop the arc energy to continue to release.arc protection and cabinet pressure plate with the program,can effectively improve power supply reliability of switchgear.