Study On Aging And Flashover Characteristics Of Composite Interface Of Cable Joint

Power cables are a key component of the power system.Cable joints are the bridge between the cables and another cables.In recent years,Cross-linked polyethylene power cables are increasingly used in power systems.The real operation experiences show that the interface between the cable insulation and the joint insulation is of the most prone to fail.With the high heat generated during the power transmission process and the micro-discharge,the insulating material is aged,the insulation degradation cause partial breakdown.Therefore,it is of great significance to study the flashover mechanism at the composite interface of cable joints and analyze the influence of defects at the composite interface on the discharge.In this paper,we study on aging and flashover characteristics of composite interface of cable joints.We explore the cable joint structure and the morphological structure of the insulating material,establish the physical flashover theory model of XLPE-SIR composite interface,analyze the entire flashover process,we design the heat aging test of the entire insulation samples.The aging samples are analyzed for hardness,scanning electron microscopy and thermal stimulation current characteristics.It shows that as the develop of the aging,the hardness of the samples increase slightly.The cross-linked polyethylene material gradually becomes brittle,cracks and microporous appear in local areas of the material surface,and the amorphous region expands;The silicone rubber material becomes wrinkled and soft,the flexibility is gradually weakened,the surface gradually wrinkles from the flat surface,and finally the local area is powdery or porous.The cross-linked polyethylene material thermally stimulated depolarization currents peak gradually moves to the low temperature region,and the peak area is getting larger and larger.By calculation,the trap energy level gradually increases with the aging.At the same time,the amount of trapped charge accumulated as the aging progresses is gradually increasing,and the density of the trap is gradually increasing as the aging progresses.Based on the interface flashover physical model and aging test research,we start the discharge test of composite interface of the cable joint.Under the power frequency voltage,we study on influence of aging on flashover performance.The results show that with the development of aging,the initial discharge voltage and flashover breakdown voltage at the interface becomes decrease tendency and the discharge current increases with the aging.Under the condition of heat aging,the silicone rubber-silicone rubber composite interface sample has the strongest voltage resistance and the highest breakdown voltage.The cross-linked polyethylene-cross-linked polyethylene composite interface has the weakest voltage resistance and the lowest breakdown voltage.Under the power frequency voltage,with the increase of pressure,the withstand voltage at the composite interface before and after aging is gradually increased.Under different aging time,the breakdown voltage increases as the electrode spacing increases.This paper contains 56 charts,14 tables and 79 references.