Disclosed is a corona-free cap assembly for achieving uniform electrical stress distribution around an electrical device having a cylindrical end, the corona-free cap assembly comprising: a clamping member configured for clamping on the cylindrical end along circumferential direction of the cylindrical end; and a corona-free cap comprising a grading chamber with two open ends, the corona-free cap further comprising a connection component fixed inside the grading chamber and adapted for connection with the clamping member in a manner that the corona-free cap is detachably fixed on the electrical device and the cylindrical end of the electrical device is at least partially extended into the grading chamber of the corona-free cap through one of the open ends.
