An improved apparatus for deconcentrating an electric field, surrounding a high voltage insulator. A clamp assembly centrally formed within a coronal ring permitting positive placement of the coronal ring about an insulator end fitting. The clamping assembly includes an integral clamp with a U-shaped opening for engaging a cylindrical portion of an insulator end fitting. Two keeper clamps are pivotally mounted superjacent to the integral clamp, each keeper clamp having a smaller U-shaped opening both of which engage a portion of the insulator end fitting and pivot toward each other between an insulator receiving position and an insulator securing position, securing the insulator between the integral clamp and the two keeper clamps. A captive fastener such as a bolt extends upwardly through the clamp and the keeper clamps to secure the keeper clamps in position against the insulator end fitting and the integral clamp to secure the corona ring in position relative the insulator end fitting. The varied sized openings of the integral clamp and keeper clamps prevent inverted installation of the corona ring.