In order to find out the cause of oil leakage of grading capacitor for 500 kV circuit breaker grading capacitor

the potential difference of the connection position of grading capacitor

performance detection of sealing ring

electrical field simulation calculation if grading capacitor and material detection of sealing end plate are performed.It is shown by the result that the potential difference at the connection position of the grading capacitor end plate is about 13.78 V

the maximum field strength at the area of fault position of end cover of grading capacitor is 2.74 kV/cm.The fundamental reason of oil leakage of grading capacitor is the electrochemical corrosion on the sealing surface of the sealing end plate.In view of the reason of the fault

the effective rectification measures are proposed.The sealing groove is changed from step into U shape and the material of the end plate is changed from LY12 aluminum bar into 6061 aluminum bar and the thickness of anode oxidation is improved to grade AA15.The grading capacitor after rectification has no oil leakage any more since 1-year operation.