corona ring

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FYH Anti-corona Ring

Corona rings are annular metal rings that are fixed to the ends of bushings and insulator strings. They are also referred to as anti-corona rings. Corona rings are used to prevent corona discharges that occur in high voltage transmission lines.

Corona Ring

Corona rings are annular metal rings that are fixed to the ends of bushings and insulator strings. They are also referred to as anti-corona rings. Corona rings are used to prevent corona discharges that occur in high voltage transmission lines. Corona discharge or corona loss is a major problem in EHV transmission lines that cause power loss. One way to reduce corona discharge is to use corona rings.

How do corona rings work?

Corona discharge occurs when the electric field (potential gradient) on the surface of a conductor exceeds a critical value, called the critical destruction voltage. The value of the critical destruction voltage varies with atmospheric conditions. The value is about 30 kV/cm. The electric field is greatest where the curvature is sharpest. Therefore, corona discharges occur first at the points of greatest curvature - i.e., suspension points, corners and edges. Corona rings are installed at these points to prevent corona formation.

Corona rings are electrically connected to conductors around points where corona discharges may occur. Thus, due to its smooth circular shape, the corona ring distributes the electric field (or charge) over a wider area. As a result, it reduces the potential gradient below the critical damage value.

Manufacturers typically recommend installing aluminum corona rings at the conductor end of string insulators for lines above 230 kV and at both ends of insulators for 500 kV.