Corona discharge refers toGas mediumstayNon-uniform electric fieldPartial self-sustaining discharge in is the most common form of gas discharge.stayRadius of curvatureNear the very small tip electrode, because the local electric field strength exceeds the ionization field strength of the gas, the gas will be ionized and excited, and corona discharge will occur.When corona occurs, light can be seen around the electrode, accompanied by a hissing sound.Corona discharge can be a relatively stable discharge form or an uneven electric field gapbreakdownThe early stage of development in the process.
The formation mechanism of corona discharge varies with the polarity of tip electrode, which is mainly due to the different accumulation and distribution of space charge during corona discharge.stayDCNegative corona orpositive electrodeThe space charge is accumulated near the tip electrode in the sexual corona.
In negative corona, when electrons cause collisionionizationAfter that, the electrons are driven to the space far away from the tip electrode, andanionAnd will gather near the electrode surfacePositive ion。electric fieldWhen strengthening continuously, positive ions are sucked into the electrode, and apulseCorona current, negative ionspreadTo the clearance space.Thereafter, the next process of ionization and charged particle movement is repeated.This cycle results in many pulsed corona currents.
The phenomenon of corona current is GW. It was discovered by Trichell in 1938 and is called the Trichell pulse.If the voltage continues to rise, the pulse frequency of corona current increasesamplitudeIncrease, change to negativeglow discharge 。When the voltage rises again, negative streamer discharge occurs, which is also called feather discharge or brush discharge due to its shape.When the negative current discharge can continue to develop to the opposite electrodeSpark dischargeTo make the whole gap breakdown.Positive ions are also distributed near the tip electrode in the positive corona, but they are constantly pushed to the gap space, while electrons are sucked into the electrode, forming repeated pulse corona current.Streaming occurs when the voltage continues to risedischargeAnd may lead to gap breakdown.
corona discharge
The discharge process of power frequency AC corona in positive and negative half cycle is basically the same as that of DC positive and negative corona.Power frequency corona current is in phase with voltage, reflecting corona power loss.External voltage and corona are often applied in engineering applicationsCharge quantityThe relationship between the two represents the corona characteristic, which is called the voltage sink characteristic of corona.[1]
corona discharge
Discharge characteristics
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Corona discharge is characterized by "hissing" sound and sometimes faint glow;When there isRadius of curvatureCorona discharge occurs when a very small tip exists.Corona discharges may or may not point in a particular direction towards other objects.During corona dischargefield strengthVery strong, the gas near the tip is ionized, and the charge can leave the conductor;However, the field strength far from the tip weakens sharply and the ionization is incomplete, so only a small current can be established.Corona discharge is characterized by a hissing sound and sometimes a faint glow.Corona discharge can be continuous or discontinuousPulse discharge。The energy density of corona discharge is far less than that of spark discharge.In some cases, if the potential of the conductor at the tip is raised, the corona will develop into a spark to another object.
The degree of non-uniformity of electric field required for corona formation is closely related to the type of gas.In a negatively charged gas, corona discharge occurs when the electrode is a spherical plane and the electrode gap is a spherical radius.On the contrary, if the gas is non negative, corona discharge will not occur.[2]
Corona dischargePolarityIt depends on the polarity of the electrode with small curvature radius.If the electrode with a small radius of curvature has a positive potential, a positive corona discharge will occur, otherwise a negative corona discharge will occur.In addition, corona discharge can also be divided into DC corona, AC corona and high-frequency corona according to the type of voltage provided.According to the number of corona electrodes, it can be divided into monopolar corona, bipolar corona and multipolar corona.[2]
Corona discharge
example
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(1) High voltage and ultrahigh voltage in power systemTransmission lineCorona on the conductor will cause corona power loss, radio interference, television interference and noise interference.When designing the line, sufficient cross-sectional area of conductor shall be selected, orBundled conductorReduce the electric field on the conductor surface to avoid corona.For high-voltage electrical equipment, corona discharge will gradually damage the insulation performance of the equipment.The space charge of corona discharge can improve the gap breakdown strength under certain conditions.When lightning orSwitching overvoltageThe overvoltage can be weakened due to corona lossamplitude。
(2) Corona discharge can be used for electrostatic precipitation, sewage treatment, air purification, etc.
(3) Trees and other pointed objects on the groundGeoelectric fieldCorona discharge is an important part of atmospheric electricity balance.
(4) The corona discharge on the sputtered water droplets on the ocean surface can promote the formation of organic matter in the ocean, and may also be one of the effective discharge forms of pre biological synthesis of amino acids in the earth's ancient atmosphere.
Figure 1: Corona discharge process and action diagram on polymer material surface[2]
(5) The energy of corona discharge can act on the surface of materials through light radiation, neutral molecular current and ion current, which is the fundamental reason for the surface modification of materials.The corona discharge process and its effect on the surface of polymer material are shown in Figure 1: Corona discharge process and its effect on the surface of polymer material.[2]
