Corona, in the context of electrical power systems, refers to a phenomenon known as "corona discharge." Corona discharge is an electrical discharge that can occur when the voltage gradient (electric field) around a conductor becomes high enough to ionize the surrounding air or insulating medium. This phenomenon is typically observed at high voltages, such as those used in high-voltage transmission lines and equipment.
Here are some key points about corona discharge and its effects on electrical power systems:
Corona Formation: When the electric field around a conductor reaches a critical value, it can ionize the air molecules around it, creating a conductive path for electrical discharge. This ionization creates a faint, bluish glow around the conductor, which is characteristic of corona discharge.
Effect on Power Loss: Corona discharge can result in energy loss from the power system. The ions formed during corona can carry away some energy, leading to increased resistive losses in the transmission line. This effect is more pronounced at higher voltages and frequencies.
Audible Noise: Corona discharge can produce audible noise, often described as a cracking or hissing sound. This noise is a result of the rapid heating and cooling of the air due to the ionization and deionization processes.
Radio Interference: Corona discharge can also generate radio frequency interference (RFI) or electromagnetic interference (EMI). These emissions can interfere with radio and communication signals in the vicinity of the corona source.
Aging and Erosion: Over time, the continuous occurrence of corona discharge can cause erosion of the conductor surface. This erosion can lead to degradation of the insulation and ultimately affect the reliability of the power system.
Mitigation: To mitigate the effects of corona, power system designers use various techniques. These include using conductors with larger diameters, reducing the electric field gradient by increasing the conductor spacing, using corona rings or corona shields on high-voltage conductors, and selecting appropriate insulation materials.
Corona Rings/Shields: These are devices placed on high-voltage conductors to distribute the electric field more evenly, reducing the likelihood of corona discharge. They can help to prevent energy loss, audible noise, and radio interference.
UV Ozone Production: Corona discharge also produces ozone due to the interaction of ionized oxygen molecules with molecular oxygen. This is why a distinct smell, often described as a "fresh" or "sharp" smell, is associated with areas where corona discharge is occurring.
Corona discharge is an important consideration in the design and operation of high-voltage power systems. Engineers and researchers work to minimize its negative effects to ensure efficient and reliable power transmission.