Study on key technology of ±800 kV UHVDC GIL

In order to improve the flexibility of transmission corridor right of way in ultra-high voltage DC system, it is necessary to study DC gas insulated metal enclosed transmission line (GIL) which can replace sections of overhead lines. Based on international test results of small-scale electrode and considering the surface roughness, the equation which can be used for estimating the critical breakdown field is deduced by using Levenberg-Marquart method. During these tests related insulator of DC GIL, the test method using the cylinder-flat electrode instead of the coaxial cylinder electrode, is presented. The DC GIL electrode which includes particle trap, particle driver and field-well ring is designed. Electric field distribution of this electrode is also emulated. The results indicate the triple structure can limit the activity of the metal conducting particle.