{"id":11204,"date":"2026-08-03T22:57:53","date_gmt":"2026-08-03T22:57:53","guid":{"rendered":"https:\/\/www.raxpower.com\/?p=11204"},"modified":"2026-08-03T22:57:53","modified_gmt":"2026-08-03T22:57:53","slug":"prevencao-por-anel-de-corona","status":"publish","type":"post","link":"https:\/\/www.raxpower.com\/pt\/blog\/corona-ring-function-prevention\/","title":{"rendered":"Fun\u00e7\u00e3o do Anel Corona: Como Evita Descargas"},"content":{"rendered":"

Uncontrolled corona discharge<\/a> doesn’t just waste energy \u2014 it eats through insulator<\/a> surfaces, generates audible noise that triggers utility complaints, and accelerates polymer aging until a string fails mid-service. For procurement managers specifying EHV hardware, that failure cost is measured in callbacks, not unit price. The corona ring<\/a> function exists to stop that cascade at the source, and getting the design wrong on paper is far cheaper than fixing it in the field. A corona ring is a circular conductive ring \u2014 usually aluminum \u2014 attached to high-voltage terminals that redistributes the electric field gradient and keeps peak field intensity below the corona threshold. Without it, the electric stress concentrates at sharp geometric points on the insulator string, and ionization begins.\n\n

We’ve seen projects where the ring diameter was undersized for the voltage class, and the result was visible corona halos on commissioning day \u2014 not something you want to explain to a utility inspector. This article walks through the physics of how corona rings manage field stress, what design variables actually move the needle on performance, and where they belong on your insulator strings across different voltage levels. We cover the toroidal field redistribution mechanism, the ring count and placement logic that matters for 220 kV and above, and how material selection holds up in coastal or industrial pollution environments.<\/p>\n

What Is Corona Discharge and Why It Happens<\/h2>\n
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Corona discharge is the visible ionization of air around high-voltage conductors when electric field strength exceeds air’s insulating capability, causing energy loss, audible noise, and equipment stress.<\/p>\n<\/blockquote>\n

When electrical infrastructure operates at high voltages, the air surrounding conductors can break down and become ionized. This phenomenon creates a faint glow, produces ozone, and generates audible hissing or crackling sounds. The process is fundamentally about electric field concentration\u2014when voltage is applied to a conductor, it creates an electrical stress field in the surrounding space. If this field becomes too intense in localized areas, it overcomes the air’s natural insulating properties.<\/p>\n

What Triggers Ionization Around High-Voltage Conductors<\/h3>\n

Ionization begins when the electric field gradient at a conductor’s surface exceeds the dielectric strength of the surrounding air. Think of it like water pressure building against a dam\u2014when the pressure becomes too concentrated at any single weak point, the structure fails. Similarly, when electric field lines cluster densely around sharp edges, irregular surfaces, or bare conductor strands, the localized stress can surpass approximately 30 kilovolts per centimeter under standard atmospheric conditions. This threshold triggers electron avalanches as free electrons in the air accelerate, collide with neutral molecules, and create additional ion pairs in a chain reaction.<\/p>\n

The physical geometry of the conductor plays a decisive role. Smooth, rounded surfaces distribute electric field lines evenly, while sharp points, burrs, or stranded conductors with protruding wires create field concentration zones. Even microscopic surface imperfections on high-voltage equipment can initiate localized ionization. This is why transmission hardware undergoes careful manufacturing and installation to minimize surface irregularities.<\/p>\n

How Voltage Level Determines Corona Onset<\/h3>\n

The relationship between voltage level and corona formation is governed by the Peek equation<\/a>, which relates onset voltage to conductor radius, surface condition, and atmospheric factors. In practical terms, corona discharge becomes increasingly likely as systems operate above 115 kilovolts, with phenomena becoming pronounced in extra-high-voltage (EHV) and ultra-high-voltage (UHV) transmission networks. However, voltage alone doesn’t tell the complete story\u2014a 230 kV line with large-diameter bundled conductors may produce less corona than a 230 kV system using single, smaller conductors.<\/p>\n

The critical parameter is actually the electric field intensity at the conductor surface, measured in kilovolts per centimeter. This intensity depends on both the applied voltage and the conductor’s effective radius. Engineers use bundled conductor configurations\u2014multiple subconductors spaced apart\u2014to effectively increase the bundle’s electromagnetic radius, thereby reducing surface field stress below the corona onset threshold. This design approach is standard practice in modern transmission line engineering.<\/p>\n

Physical Conditions That Enable Corona Discharge<\/h3>\n

Atmospheric conditions dramatically influence corona behavior. Air density, which decreases with altitude and temperature, reduces the dielectric strength of the surrounding medium. At higher elevations, corona onset voltages drop significantly\u2014approximately 1% reduction per 100 meters above sea level. Humidity also affects breakdown characteristics, though the relationship is complex; moist air can actually increase corona onset voltage slightly under certain conditions due to electron attachment forming heavier, slower negative ions.<\/p>\n