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Through folding screen of dendritic discharge in Fushun Power Supply Company 220kV Gongnong Station, this paper folding screen in the basic process of dendritic discharge fault, argument insulation be affected with damp be affected with damp and gas are the main external cause the folding screen dendritic discharge fault; Insulation structure defects are the main internal cause folding screen dendritic discharge fault. Combined with the actual finally puts forward the measures to prevent the folding screen dendritic discharge fault. Introduction Folding screen dendritic discharge accident is not allow to ignore.This kind of accidents occur mostly on the three-phase transformer, unless the light gas relay action, and promptly blackout check repair. Otherwise, when a heavy gas relay action or differential protection action, the transformer will be a serious distortion, sometimes box along the bolt fracture, transformer oil leaked out, and the consequence is very serious. Due to the transformer winding head pad and stay insulated structure exist edges, making the conductor edges in the electric field distortion. And folding screen and winding inside the protrusions (block), S bending transposition and turns uneven deformation and paperboard bending part, narrow the local oil duct, both may cause local overheating, but also intensified electric field distortion, field strength increased. Therefore, will cause the wire on the surface of the edges of the insulation oil gap occurs first discharge, then development to the folding screen board, or cause the second oil gap discharge, or along the inside surface and the interlayer sliding folding screen board flash discharge. When interlayer unclean (water or air bubbles), internal slide flash discharge is more likely to happen, finally in the plasma channel "dendritic" char is formed on the channel[1-3]. The cause of the folding screen dendritic discharge (1)The main external cause 1) Wet insulation The dry oil gap and cardboard folding screen structure of the electric strength is high. After the oil cut insulation board be affected with damp be affected with damp, however, its electric strength will be greatly reduced. Moisture intrusion approach generally has safe airway, hygroscopic and transformer oil pump, catheter anastomoses. When internal moisture from the way into the fuel tank, the transformer oilpaper insulation be affected with damp be affected with damp, oiled paper insulated electrical strength will be greatly reduced, trigger a folding screen dendritic discharge failure[4, 5]. 2) Insulating gas Another reason is caused by the large transformer screens dendritic discharge gas in transformer oil. Because the gas will make the discharge inception field strength greatly reduced, especially when high gas content in transformer, and moisture intrusion, because the screen board is attached to the surface moisture bubbles, or cardboard sandwich bubble, stratified and the existence of moisture whole, will be easier to form the tree discharge.

Analysis of 220kV Main Transformer Screens Dendritic Discharge Fault