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How to prevent corona discharge during cable partial discharge test

source:Industry News    release time:2022-06-15    Article author:sznbone     Popular:saso power plug

  Heng-well European 2 Prong 250v 2.5A Europe Plug 2 Pin Eu Power Cord

  First, under the action of DC voltage, both positive and negative corona electrodes accumulate space charges near the tip electrode. In a negative corona, when the electrons are ionized by collision, the electrons are driven to the space away from the tip electrode to form negative ions, and odd positive ions are gathered near the electrode surface. When the electric field continues to strengthen, the positive ions are sucked into the electrode. When a pulse current occurs, the negative ions diffuse into the interstitial space. After that, the next process of ionization and charged particle motion is repeated. This cycle is such that many pulses of corona current occur. If the voltage continues to increase, the pulse frequency of the corona current increases, the negative value increases, and it transforms into a glow discharge. When the voltage rises again, a negative streamer discharge occurs. Because of its shape, it is also called a plume discharge or a brush discharge. . When the negative streamer discharge can continue to develop to the opposite electrode, it will cause a spark discharge, which will break down the entire gap. The positive corona also distributes positive ions near the tip electrode, but is constantly repelled to the interstitial space, while electrons are drawn into the electrode, which also forms a repeating pulse current corona. As the voltage continues to rise, streamer discharge occurs and can lead to gap breakdown.

  Corona discharge is characterized by a "hissing" sound and sometimes a faint glow. Corona discharge occurs when there is a small tip on the surface of the conductor. Corona discharges may or may not be directed towards other objects in a particular direction. During corona discharge, the electric field strength near the tip is very strong, the gas near the tip is ionized, and the charge can leave the conductor; while the field strength is sharply weakened away from the tip, and the ionization is incomplete, so only a tiny current can be established. Corona discharges are characterized by a "hissing" sound and sometimes a faint glow. Corona discharge can be continuous discharge or continuous pulse discharge. The energy density of corona discharge is much smaller than that of spark discharge. In some cases, if the potential of the tip conductor is raised, the corona can develop into a spark to another object. When the finished product is inspected for the withstand voltage test, be sure to insert the conductor part into the copper connector, tighten the fixing screw to make it firmly fixed to the cable head, and carefully wipe the exposed part of the insulation with cotton cloth and anhydrous alcohol. Poor contact also leads to tip corona discharge. When the three insulated wire cores are subjected to the high-voltage test, the insulating medium must be separated to prevent corona discharge from each other. When stripping the head, strictly follow the operating rules and use a planer to strip the semi-conductive shielding layer from the end of the cable inward, and strip the insulation and Conductor shielding, the stripping length is 8.7/15KV and below and more than 15cm, and 12/20KV~20/35KV is more than 20cm. The stripping thickness is required to just strip off the insulating semiconducting shielding layer. Pay attention to the last retraction action, the root should be rounded, No sharp corners are allowed, and the peeled insulating part is not allowed to have deep knife marks or black semi-conductive shielding layer residues. When using a large terminal, it is advisable to strip off the insulation and conductor shield so that the conductor is exposed by 5cm. For a small terminal, only the outer shield needs to be stripped, and no sharp points are allowed on the surface.

  The occurrence of corona, for high-voltage electrical equipment, will gradually destroy the insulation performance of the equipment, and the space charge of corona discharge has the effect of improving the gap breakdown strength under certain conditions. When doing the withstand voltage test, it is necessary to strengthen preventive measures to prevent the occurrence of corona discharge and improve the inspection efficiency of finished products.


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