Corona ring

Corona rings on 380 kV line insulators

400 kV power lines with corona rings on insulators

This Cockcroft–Walton voltage multiplier was part of one of the early particle accelerators responsible for development of the atomic bomb. Built in 1937 by Philips of Eindhoven, it is now in the National Science Museum in London, England. Note the silver corona rings around the insulators.

A corona ring, also called anti-corona ring, is a toroid of (typically) conductive material located in the vicinity of a terminal of a high voltage device. It is electrically insulated. Stacks of more spaced rings are often used. The role of the corona ring is to distribute the electric field gradient and lower its maximum values below the corona threshold, preventing the corona discharge.

Corona rings are often seen on van de Graaf generators, electrical insulators, Cockcroft–Walton generators, particle accelerators, Lightning Arresters, high voltage bushing terminals, and other high voltage equipment.

Corona rings are typically installed on very high voltage power line insulators. Manufacturers suggest a corona ring on the line end of the insulator for above 230 kV and on both ends for above 500 kV. Corona rings prolong lifetime of insulator surfaces by suppressing the effects of corona discharge.^[1]

Corona rings may also be installed on the insulators of antennas of high-power radio transmitters.^[2] They increase, however, the capacitance of the insulators.^[3]

Corona discharge is a more serious problem in higher altitude locations, where the air is less dense.

Corona caps are caps with round edges; they are mounted on the ends of the insulators and play the same role as corona rings.

See also

• Arcing horns

References

1. ^ Electric power generation, transmission, and distribution, Volume 1 By Leonard L. Grigsby, CRC Press, 2007, ISBN 0849392926
2. ^ The Handbook of antenna design, Volume 2 By Alan W. Rudge, IET, 1983, p. 873, ISBN 0906048877
3. ^ aerials for metre and decimetre wave-lengths, CUP Archive